Impact of acquisition and modeling parameters on the test-retest reproducibility of edited GABA

Literature values vary widely for within-subject test-retest reproducibility of gamma-aminobutyric acid (GABA) measured with edited magnetic resonance spectroscopy (MRS). Reasons for this variation remain unclear. Here, we tested whether three acquisition parameters-(1) sequence complexity (two-experiment MEscher-GArwood Point RESolved Spectroscopy [MEGA-PRESS] vs. four-experiment Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy [HERMES]); (2) editing pulse duration (14 vs. 20 ms); and (3) scanner frequency drift (interleaved water referencing [IWR] turned ON vs. OFF)-and two linear combination modeling variations-(1) three different coedited macromolecule models (called "1to1GABA", "1to1GABAsoft", and "3to2MM" in the Osprey software package); and (2) 0.55- versus 0.4-ppm spline baseline knot spacing-affected the within-subject coefficient of variation of GABA + macromolecules (GABA+). We collected edited MRS data from the dorsal anterior cingulate cortex from 20 participants (mean age: 30.8 ± 9.5 years; 10 males). Test and retest scans were separated by removing the participant from the scanner for 5-10 min. Each acquisition consisted of two MEGA-PRESS and two HERMES sequences with editing pulse durations of 14 and 20 ms (referred to here as MEGA-14, MEGA-20, HERMES-14, and HERMES-20; all TE = 80 ms, 224 averages). We identified the best test-retest reproducibility following postprocessing with a composite model of the 0.9- and 3-ppm macromolecules ("3to2MM"); this model performed particularly well for the HERMES data. Furthermore, sparser (0.55- compared with 0.4-ppm) spline baseline knot spacing yielded generally better test-retest reproducibility for GABA+. Replicating our prior results, linear combination modeling in Osprey compared with simple peak fitting in Gannet resulted in substantially better test-retest reproducibility. However, reproducibility did not consistently differ for MEGA-PRESS compared with HERMES, for 14- compared with 20-ms editing pulses, or for IWR-ON versus IWR-OFF. These results highlight the importance of model selection for edited MRS studies of GABA+, particularly for clinical studies that focus on individual patient differences in GABA+ or changes following an intervention.

Parameter Space and Potential for Biomarker Development in 25 Years of fMRI Drug Cue Reactivity: A Systematic Review

Importance

In the last 25 years, functional magnetic resonance imaging drug cue reactivity (FDCR) studies have characterized some core aspects in the neurobiology of drug addiction. However, no FDCR-derived biomarkers have been approved for treatment development or clinical adoption. Traversing this translational gap requires a systematic assessment of the FDCR literature evidence, its heterogeneity, and an evaluation of possible clinical uses of FDCR-derived biomarkers.

Objective

To summarize the state of the field of FDCR, assess their potential for biomarker development, and outline a clear process for biomarker qualification to guide future research and validation efforts.

Evidence Review

The PubMed and Medline databases were searched for every original FDCR investigation published from database inception until December 2022. Collected data covered study design, participant characteristics, FDCR task design, and whether each study provided evidence that might potentially help develop susceptibility, diagnostic, response, prognostic, predictive, or severity biomarkers for 1 or more addictive disorders.

Findings

There were 415 FDCR studies published between 1998 and 2022. Most focused on nicotine (122 [29.6%]), alcohol (120 [29.2%]), or cocaine (46 [11.1%]), and most used visual cues (354 [85.3%]). Together, these studies recruited 19 311 participants, including 13 812 individuals with past or current substance use disorders. Most studies could potentially support biomarker development, including diagnostic (143 [32.7%]), treatment response (141 [32.3%]), severity (84 [19.2%]), prognostic (30 [6.9%]), predictive (25 [5.7%]), monitoring (12 [2.7%]), and susceptibility (2 [0.5%]) biomarkers. A total of 155 interventional studies used FDCR, mostly to investigate pharmacological (67 [43.2%]) or cognitive/behavioral (51 [32.9%]) interventions; 141 studies used FDCR as a response measure, of which 125 (88.7%) reported significant interventional FDCR alterations; and 25 studies used FDCR as an intervention outcome predictor, with 24 (96%) finding significant associations between FDCR markers and treatment outcomes.

Conclusions and Relevance

Based on this systematic review and the proposed biomarker development framework, there is a pathway for the development and regulatory qualification of FDCR-based biomarkers of addiction and recovery. Further validation could support the use of FDCR-derived measures, potentially accelerating treatment development and improving diagnostic, prognostic, and predictive clinical judgments.

Alcohol Cue Processing in Co-Occurring Bipolar Disorder and Alcohol Use Disorder

Importance

Reward circuitry dysfunction is a candidate mechanism of co-occurring bipolar disorder and alcohol use disorder (BD + AUD) that remains understudied. This functional magnetic resonance imaging (fMRI) research represents the first evaluation of alcohol cue reward processing in BD + AUD.

Objective

To determine how alcohol cue processing in individuals with BD + AUD may be distinct from that of individuals with AUD or BD alone.

Design, Setting, and Participants

This cross-sectional case-control study (April 2013-June 2018) followed a 2 × 2 factorial design and included individuals with BD + AUD, AUD alone, BD alone, and healthy controls. A well-validated visual alcohol cue reactivity fMRI paradigm was administered to eligible participants following their demonstration of 1 week or more of abstinence from alcohol and drugs assessed via serial biomarker testing. Study procedures were completed at the Medical University of South Carolina. Analysis took place between June and August 2022.

Main Outcomes and Measures

Past-week mood symptoms were rated by clinicians using the Montgomery-Åsberg Depression Rating Scale and Young Mania Rating Scale. The Alcohol Dependence Scale, Obsessive-Compulsive Drinking Scale, and Barratt Impulsiveness Scale were included questionnaires. Functional MRI whole-brain data were analyzed along with percent signal change within a priori regions of interest located in the ventral striatum, dorsal striatum, and ventromedial prefrontal cortex. Exploratory analyses of associations between cue reactivity and select behavioral correlates (alcohol craving, impulsivity, maximum number of alcohol drinks on a single occasion, and days since last alcohol drink) were also performed.

Results

Of 112 participants, 28 (25.0%) had BD + AUD, 26 (23.2%) had AUD alone, 31 (27.7%) had BD alone, and 27 (24.1%) were healthy controls. The mean (SD) age was 38.7 (11.6) years, 50 (45.5%) were female, 33 (30%) were smokers, and 37 (34.9%) reported recent alcohol consumption. Whole-brain analyses revealed a BD × AUD interaction (F = 10.64; P = .001; η2 = 0.09) within a cluster spanning portions of the right inferior frontal gyrus and insula. Region of interest analyses revealed a main association of BD (F = 8.02; P = .006; η2 = 0.07) within the dorsal striatum. In each instance, individuals with BD + AUD exhibited reduced activation compared with all other groups who did not significantly differ from one another. These hypoactivations were associated with increased impulsivity and obsessive-compulsive alcohol craving exclusively among individuals with BD + AUD.

Conclusion and Relevance

The findings of this study suggest conceptualizing reward dysfunction in BD + AUD by the potential interaction between blunted reward responsivity and deficient inhibitory control may help guide treatment development strategies. To this end, reduced right inferior frontal gyrus and insula alcohol cue reactivity represents a novel candidate biomarker of BD + AUD that may respond to pharmacological interventions targeting impulsivity-related neural mechanisms for improved executive control.

N-acetylcysteine does not alter neurometabolite levels in non-treatment seeking adolescents who use alcohol heavily: A preliminary randomized clinical trial

Current treatments for adolescent alcohol use disorder (AUD) are mainly psychosocial and limited in their efficacy. As such, pharmacotherapies are being investigated as potential adjunctive treatments to bolster treatment outcomes. N-acetylcysteine is a promising candidate pharmacotherapy for adolescent AUD because of its tolerability and demonstrated ability to modulate glutamatergic, GABAergic, and glutathione systems. The primary objective of this double-blind, placebo-controlled, within-subjects crossover preliminary investigation was to measure potential changes within glutamate + glutamine (Glx), GABA, and glutathione levels in the dorsal anterior cingulate cortex (dACC) using proton magnetic resonance spectroscopy during 10-days of N-acetylcysteine (1200 mg twice daily) compared to 10-days of placebo in non-treatment seeking adolescents who use alcohol heavily (N = 31; 55% female). Medication adherence was confirmed via video. Effects on alcohol use were measured using Timeline Follow-Back as an exploratory aim. Linear mixed effects models controlling for baseline metabolite levels, brain tissue composition, alcohol use, cannabis use, and medication adherence found no significant differences in Glx, GABA, or glutathione levels in the dACC after N-acetylcysteine compared to placebo. There were also no measurable effects on alcohol use; however, this finding was underpowered. Findings were consistent in the subsample of participants who met criteria for AUD (n = 19). The preliminary null findings in brain metabolite levels may be due to the young age of participants, relatively low severity of alcohol use, and non-treatment seeking status of the population investigated. Future studies can use these findings to conduct larger, well-powered studies within adolescents with AUD.

Impact of acquisition and modeling parameters on test-retest reproducibility of edited GABA

Literature values for within-subject test-retest reproducibility of gamma-aminobutyric acid (GABA), measured with edited magnetic resonance spectroscopy (MRS), vary widely. Reasons for this variation remain unclear. Here we tested whether sequence complexity (two-experiment MEGA-PRESS versus four-experiment HERMES), editing pulse duration (14 versus 20 ms), scanner frequency drift (interleaved water referencing (IWR) turned ON versus OFF), and linear combination modeling variations (three different co-edited macromolecule models and 0.55 versus 0.4 ppm spline baseline knot spacing) affected the within-subject coefficient of variation of GABA + macromolecules (GABA+). We collected edited MRS data from the dorsal anterior cingulate cortex from 20 participants (30.8 ± 9.5 years; 10 males). Test and retest scans were separated by removing the participant from the scanner for 5-10 minutes. Each acquisition consisted of two MEGA-PRESS and two HERMES sequences with editing pulse durations of 14 and 20 ms (referred to here as: MEGA-14, MEGA-20, HERMES-14, and HERMES-20; all TE = 80 ms, 224 averages). Reproducibility did not consistently differ for MEGA-PRESS compared with HERMES or for 14 compared with 20 ms editing pulses. A composite model of the 0.9 and 3 ppm macromolecules (particularly for HERMES) and sparser (0.55 compared with 0.4 ppm) spline baseline knot spacing yielded generally better test-retest reproducibility for GABA+. Replicating our prior results, linear combination modeling in Osprey compared with simple peak fitting in Gannet resulted in substantially better test-retest reproducibility. These results highlight the importance of model selection for edited MRS studies of GABA+, particularly for clinical studies which focus on individual patient differences in GABA+ or changes following an intervention.

More than one-half of the variance in in vivo proton MR spectroscopy metabolite estimates is common to all metabolites

The present study characterized associations among brain metabolite levels, applying bivariate and multivariate (i.e., factor analysis) statistical methods to total creatine (tCr)-referenced estimates of the major Point RESolved Spectroscopy (PRESS) proton MR spectroscopy (¹ H-MRS) metabolites (i.e., total NAA/tCr, total choline/tCr, myo-inositol/tCr, glutamate + glutamine/tCr) acquired at 3 T from medial parietal lobe in a large (n = 299), well-characterized international cohort of healthy volunteers. Results supported the hypothesis that ¹ H-MRS-measured metabolite estimates are moderately intercorrelated (M_r  = 0.42, SD_r  = 0.11, ps < 0.001), with more than one-half (i.e., 57%) of the total variability in metabolite estimates explained by a single common factor. Older age was significantly associated with lower levels of the identified common metabolite variance (CMV) factor (β = -0.09, p = 0.048), despite not being associated with levels of any individual metabolite. Holding CMV factor levels constant, females had significantly lower levels of total choline (i.e., unique metabolite variance; β = -0.19, p < 0.001), mirroring significant bivariate correlations between sex and total choline reported previously. Supplementary analysis of water-referenced metabolite estimates (i.e., including tCr/water) demonstrated lower, although still substantial, intercorrelations among metabolites, with 37% of total metabolite variance explained by a single common factor. If replicated, these results would suggest that applied ¹ H-MRS researchers shift their analytical framework from examining bivariate associations between individual metabolites and specialty-dependent (e.g., clinical, research) variables of interest (e.g., using t-tests) to examining multivariable (i.e., covariate) associations between multiple metabolites and specialty-dependent variables of interest (e.g., using multiple regression).

A methodological checklist for fMRI drug cue reactivity studies: development and expert consensus

Cue reactivity is one of the most frequently used paradigms in functional magnetic resonance imaging (fMRI) studies of substance use disorders (SUDs). Although there have been promising results elucidating the neurocognitive mechanisms of SUDs and SUD treatments, the interpretability and reproducibility of these studies is limited by incomplete reporting of participants' characteristics, task design, craving assessment, scanning preparation and analysis decisions in fMRI drug cue reactivity (FDCR) experiments. This hampers clinical translation, not least because systematic review and meta-analysis of published work are difficult. This consensus paper and Delphi study aims to outline the important methodological aspects of FDCR research, present structured recommendations for more comprehensive methods reporting and review the FDCR literature to assess the reporting of items that are deemed important. Forty-five FDCR scientists from around the world participated in this study. First, an initial checklist of items deemed important in FDCR studies was developed by several members of the Enhanced NeuroImaging Genetics through Meta-Analyses (ENIGMA) Addiction working group on the basis of a systematic review. Using a modified Delphi consensus method, all experts were asked to comment on, revise or add items to the initial checklist, and then to rate the importance of each item in subsequent rounds. The reporting status of the items in the final checklist was investigated in 108 recently published FDCR studies identified through a systematic review. By the final round, 38 items reached the consensus threshold and were classified under seven major categories: 'Participants' Characteristics', 'General fMRI Information', 'General Task Information', 'Cue Information', 'Craving Assessment Inside Scanner', 'Craving Assessment Outside Scanner' and 'Pre- and Post-Scanning Considerations'. The review of the 108 FDCR papers revealed significant gaps in the reporting of the items considered important by the experts. For instance, whereas items in the 'General fMRI Information' category were reported in 90.5% of the reviewed papers, items in the 'Pre- and Post-Scanning Considerations' category were reported by only 44.7% of reviewed FDCR studies. Considering the notable and sometimes unexpected gaps in the reporting of items deemed to be important by experts in any FDCR study, the protocols could benefit from the adoption of reporting standards. This checklist, a living document to be updated as the field and its methods advance, can help improve experimental design, reporting and the widespread understanding of the FDCR protocols. This checklist can also provide a sample for developing consensus statements for protocols in other areas of task-based fMRI.

Results from a randomized, double-blind, placebo-controlled, crossover, multimodal-MRI pilot study of gabapentin for co-occurring bipolar and cannabis use disorders

Disrupted brain gamma-aminobutyric acid (GABA)/glutamate homeostasis is a promising target for pharmacological intervention in co-occurring bipolar disorder (BD) and cannabis use disorder (CUD). Gabapentin is a safe and well-tolerated medication, FDA-approved to treat other neurological diseases, that restores GABA/glutamate homeostasis, with treatment studies supporting efficacy in treating CUD, as well as anxiety and sleep disorders that are common to both BD and CUD. The present manuscript represents the primary report of a randomized, double-blind, placebo-controlled, crossover (1-week/condition), multimodal-MRI (proton-MR spectroscopy, functional MRI) pilot study of gabapentin (1200 mg/day) in BD + CUD (n = 22). Primary analyses revealed that (1) gabapentin was well tolerated and adherence and retention were high, (2) gabapentin increased dorsal anterior cingulate cortex (dACC) and right basal ganglia (rBG) glutamate levels and (3) gabapentin increased activation to visual cannabis cues in the posterior midcingulate cortex (pMCC, a region involved in response inhibition to rewarding stimuli). Exploratory evaluation of clinical outcomes further found that in participants taking gabapentin versus placebo, (1) elevations of dACC GABA levels were associated with lower manic/mixed and depressive symptoms and (2) elevations of rBG glutamate levels and pMCC activation to cannabis cues were associated with lower cannabis use. Though promising, the findings from this study should be interpreted with caution due to observed randomization order effects on dACC glutamate levels and identification of statistical moderators that differed by randomization order (i.e. cigarette-smoking status on rBG glutamate levels and pMCC cue activation). Nonetheless, they provide the necessary foundation for a more robustly designed (urn-randomized, parallel-group) future study of adjuvant gabapentin for BD + CUD.

Importance of Linear Combination Modeling for Quantification of Glutathione and γ-Aminobutyric Acid Levels Using Hadamard-Edited Magnetic Resonance Spectroscopy

BACKGROUND

J-difference-edited ¹H-MR spectra require modeling to quantify signals of low-concentration metabolites. Two main approaches are used for this spectral modeling: simple peak fitting and linear combination modeling (LCM) with a simulated basis set. Recent consensus recommended LCM as the method of choice for the spectral analysis of edited data.

PURPOSE

The aim of this study is to compare the performance of simple peak fitting and LCM in a test-retest dataset, hypothesizing that the more sophisticated LCM approach would improve quantification of Hadamard-edited data compared with simple peak fitting.

METHODS

A test-retest dataset was re-analyzed using Gannet (simple peak fitting) and Osprey (LCM). These data were obtained from the dorsal anterior cingulate cortex of twelve healthy volunteers, with TE = 80 ms for HERMES and TE = 120 ms for MEGA-PRESS of glutathione (GSH). Within-subject coefficients of variation (CVs) were calculated to quantify between-scan reproducibility of each metabolite estimate.

RESULTS

The reproducibility of HERMES GSH estimates was substantially improved using LCM compared to simple peak fitting, from a CV of 19.0-9.9%. For MEGA-PRESS GSH data, reproducibility was similar using LCM and simple peak fitting, with CVs of 7.3 and 8.8%. GABA + CVs from HERMES were 16.7 and 15.2%, respectively for the two models.

CONCLUSION

LCM with simulated basis functions substantially improved the reproducibility of GSH quantification for HERMES data.

Effects of Gabapentin on Dorsal Anterior Cingulate Cortex GABA and Glutamate Levels and Their Associations With Abstinence in Alcohol Use Disorder: A Randomized Clinical Trial

OBJECTIVE

Although gabapentin has demonstrated efficacy in mitigating alcohol withdrawal symptoms and preventing relapse drinking in individuals with alcohol use disorder (AUD), the neurobiological mechanisms of action underlying these therapeutic effects remain unknown. The present study evaluated changes in GABA and glutamate levels in the dorsal anterior cingulate cortex (dACC) as candidate mechanisms of action.

METHODS

In a 16-week randomized clinical trial, 68 adults with AUD, including a history of alcohol withdrawal syndrome, received 1,200 mg/day of gabapentin (N=37) or placebo (N=31) and nine medical management visits after ≥72 hours of abstinence. Proton MR spectroscopy (¹H-MRS) estimates of dACC levels of GABA (N=67) and glutamate (N=64) were acquired before start of treatment and again approximately 14 days after randomization. Percent days abstinent was reported via timeline followback interview.

RESULTS

The effects of gabapentin on GABA and glutamate levels were significantly associated with participants' percent days abstinent during early treatment. Specifically, gabapentin was associated with greater increases in glutamate and greater decreases in GABA levels in participants who remained mostly or entirely abstinent, and yet the opposite in participants who drank on more than half of the days preceding the second scan. Furthermore, gabapentin-treated participants with greater increases in glutamate levels during early treatment had significantly more percent days abstinent across the remainder of the study, relative to placebo-treated participants.

CONCLUSIONS

In addition to providing insight into the mechanisms through which gabapentin may promote abstinence in individuals with AUD, this study also provides evidence for a biomarker of efficacious treatment that may be used to evaluate other glutamatergic or GABAergic medications for AUD and related conditions.

A Multimethod Examination of Sensitivity to Reward and Sensitivity to Punishment in Bipolar Disorder and Alcohol Dependence: Results from a 2 × 2 Factorial Design

INTRODUCTION

Shared neurobehavioral characteristics of bipolar disorder (BD) and alcohol dependence (AD), including heightened sensitivity to reward (SR), may account for high rates of BD and AD co-occurrence (BD + AD). However, empirical research is lacking. The present multimethod investigation examined SR and sensitivity to punishment (SP) among these patient groups using a reliable and well-validated self-report questionnaire of SR and SP along with a laboratory task specifically designed to distinguish SR and SP activation.

METHODS

One-hundred participants formed 4 groups: BD + AD (n = 40), BD (n = 18), AD (n = 25), and healthy controls (n = 17). Clinical interviews were administered, and participants completed the Sensitivity to Punishment and Sensitivity to Reward Questionnaire (SPSR-Q) and the Point Score Reaction Test behavioral task. Pearson correlations, hierarchical linear regression, and 2 × 2 factorial general linear modeling with Bonferroni-corrected pairwise comparisons were performed.

RESULTS

BD and AD main effects were significant on self-reported SR and SP; however, BD × AD interactions were not. BD + AD individuals were significantly higher on self-reported SR than BD and AD individuals, yet all clinical groups were similar on SP. Behavioral response times did not distinguish groups nor did they associate with self-report data.

DISCUSSION/CONCLUSION

BD and AD had additive, rather than interactive, effects on self-reported SR and SP. The methods employed, paired with their application to the present sample, may account for a lack of positive findings with behavioral data.

Intraindividual changes in brain GABA, glutamate, and glutamine during monitored abstinence from alcohol in treatment-naive individuals with alcohol use disorder

Proton magnetic resonance spectroscopy (¹ H-MRS) studies have demonstrated abnormal levels of a variety of neurometabolites in treatment-seeking individuals with moderate-severe alcohol use disorder (AUD) following acute withdrawal. In contrast, few studies have investigated neurochemical changes across early abstinence in less severe, treatment-naïve AUD. The present study, which represents the primary report of a research grant from ABMRF/The Alcohol Research Fund, measured dorsal anterior cingulate cortex (dACC) GABA, glutamate, and glutamine levels in treatment-naïve AUD (n = 23) via three ¹ H-MRS scans spaced across a planned week of abstinence from alcohol. In addition to AUD participants, 12 light drinkers completed two scans, separated by 48 hours, to ensure that results in AUD were not produced by between-scan differences other than abstinence from alcohol. ¹ H-MRS spectra were acquired in dACC at each scan using 2D J-resolved point-resolved spectroscopy. Linear mixed modeling results demonstrated a significant increase in GABA, but not glutamate or glutamine (Ps = .237-.626), levels between scans 1 and 2 (+8.88%, .041), with no difference between scans 2 and 3 (+1.00%, .836), in AUD but not LD (F = 1.24, .290) participants. Exploratory regression analyses tentatively revealed a number of significant prospective associations between changes in glutamine levels and heavy drinking, craving, and withdrawal symptoms. Most notably, the present study demonstrated return from abnormally low to normal GABA levels in treatment-naïve AUD within 3 days of their last drink; the pattern of results was consistent with glutamate and glutamine disturbances being exclusive to relatively more severe AUD.

Comparison of Multivendor Single-Voxel MR Spectroscopy Data Acquired in Healthy Brain at 26 Sites

Background The hardware and software differences between MR vendors and individual sites influence the quantification of MR spectroscopy data. An analysis of a large data set may help to better understand sources of the total variance in quantified metabolite levels. Purpose To compare multisite quantitative brain MR spectroscopy data acquired in healthy participants at 26 sites by using the vendor-supplied single-voxel point-resolved spectroscopy (PRESS) sequence. Materials and Methods An MR spectroscopy protocol to acquire short-echo-time PRESS data from the midparietal region of the brain was disseminated to 26 research sites operating 3.0-T MR scanners from three different vendors. In this prospective study, healthy participants were scanned between July 2016 and December 2017. Data were analyzed by using software with simulated basis sets customized for each vendor implementation. The proportion of total variance attributed to vendor-, site-, and participant-related effects was estimated by using a linear mixed-effects model. P values were derived through parametric bootstrapping of the linear mixed-effects models (denoted Pboot). Results In total, 296 participants (mean age, 26 years ± 4.6; 155 women and 141 men) were scanned. Good-quality data were recorded from all sites, as evidenced by a consistent linewidth of N-acetylaspartate (range, 4.4-5.0 Hz), signal-to-noise ratio (range, 174-289), and low Cramér-Rao lower bounds (≤5%) for all of the major metabolites. Among the major metabolites, no vendor effects were found for levels of myo-inositol (Pboot > .90), N-acetylaspartate and N-acetylaspartylglutamate (Pboot = .13), or glutamate and glutamine (Pboot = .11). Among the smaller resonances, no vendor effects were found for ascorbate (Pboot = .08), aspartate (Pboot > .90), glutathione (Pboot > .90), or lactate (Pboot = .28). Conclusion Multisite multivendor single-voxel MR spectroscopy studies performed at 3.0 T can yield results that are coherent across vendors, provided that vendor differences in pulse sequence implementation are accounted for in data analysis. However, the site-related effects on variability were more profound and suggest the need for further standardization of spectroscopic protocols. © RSNA, 2020 Online supplemental material is available for this article.

An evaluation of the reproducibility of 1H-MRS GABA and GSH levels acquired in healthy volunteers with J-difference editing sequences at varying echo times

Recent advances in J-difference-edited proton magnetic resonance spectroscopy (¹H MRS) data acquisition and processing have led to the development of Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy (HERMES) techniques, which enable the simultaneous measurement of ɣ-aminobutyric acid (GABA), the primary inhibitory amino acid neurotransmitter in the central nervous system, and of glutathione (GSH), the most abundant antioxidant in living tissue, at the commonly available magnetic field strength of 3 T. However, the reproducibility of brain levels of GABA and GSH measured across multiple scans in human subjects using HERMES remains to be established. In the present study, twelve healthy volunteers completed two consecutive HERMES scans of the dorsal anterior cingulate cortex (dACC) to assess the test-retest reproducibility of the technique for GABA and GSH measurements at TE = 80 ms. Eleven of the twelve participants additionally completed two consecutive MEGA-PRESS scans at TE = 120 ms, with editing pulses configured for GSH acquisition, to compare the reliability of GSH in the same voxel measured using the standard MEGA-PRESS at TE = 120 ms. The primary findings of study were that, 1) the coefficient of variation (CV) of measuring GABA with HERMES was 16.7%, which is in agreement with the reliability we previously reported for measuring GABA using MEGA-PRESS; and 2) the reliability of measuring GSH with MEGA-PRESS at TE = 120 ms was more than twice as high as that for measuring the antioxidant with HERMES at TE = 80 ms (CV = 7.3% vs. 19.0% respectively). These findings suggest that HERMES and MEGA-PRESS offer similar reliabilities for measuring GABA, while MEGA-PRESS at TE = 120 ms is more reliable for measuring GSH relative to HERMES at TE = 80 ms.

Delay discounting and reward sensitivity in a 2 × 2 study of bipolar disorder and alcohol dependence

BACKGROUND AND AIMS

Separate studies have shown increased delay discounting in people with bipolar disorder (BD) and people with alcohol dependence (AD) relative to people without mental health problems. Delay discounting was compared in people with no mental health problems, AD, BD and AD plus BD. Associations of delay discounting with self-reported impulsivity and reward sensitivity were also assessed.

DESIGN

The study was a two-by-two factorial comparative observational design.

SETTING

Data were collected at baseline diagnostic visits as part of a neuroimaging study at a medical university in South Carolina, USA.

PARTICIPANTS

Twenty-two BD + AD, 33 BD, 28 AD and 27 people without mental health problems participated.

MEASUREMENTS

Diagnostic and clinician-rated symptom measures, self-report questionnaires and a computerized delay discounting task were administered. Two-by-two general linear univariate models were tested to examine between-group differences on discounting rates, and bivariate correlations and hierarchical regression analyses were performed to examine associations between discounting rates and self-reported reward sensitivity and impulsivity.

FINDINGS

There was a significant main effect of AD (P = 0.006, η2  = 0.068). The main effect of BD and the BD × AD interaction terms were non-significant (P ≥ 0.293, η2  ≤ 0.010). Reward sensitivity and impulsivity were not significantly associated with discounting rates after adjustment for the other (P ≥ 0.089).

CONCLUSIONS

People with alcohol dependence appear to have higher delay discounting, while previously found associations between bipolar disorder and delay discounting may be secondary to alcohol use disorder.

Evidence for a unique association between fronto-cortical glycine levels and recent heavy drinking in treatment naïve individuals with alcohol use disorder

Although the neurotransmitters/modulators glutamate and, more recently, glycine have been implicated in the development and maintenance of Alcohol Use Disorder (AUD) in preclinical research, human proton magnetic resonance spectroscopy (¹H-MRS) studies have focused solely on the measurement of glutamate. The purpose of the present analysis was to examine the relative associations of brain glutamate and glycine levels with recent heavy drinking in 41 treatment naïve individuals with AUD using ¹H-MRS. The present study is the first that we are aware of to report in vivo brain glycine levels from an investigation of addiction. Dorsal Anterior Cingulate Cortex (dACC) glutamate and glycine concentration estimates were obtained using Two-Dimensional J-Resolved Point Resolved Spectroscopy at 3 Tesla, and past 2-week summary estimates of alcohol consumption were assessed via the Timeline Followback method. Glutamate (β = -0.44, t = -3.09, p = 0.004) and glycine (β = -0.68, t = -5.72, p <  0.001) were each significantly, inversely associated with number of heavy drinking days when considered alone. However, when both variables were simultaneously entered into a single regression model, the effect of glutamate was no longer significant (β = -0.11, t = -0.81, p = 0.42) whereas the effect of glycine remained significant (β = -0.62, t = -4.38, p < 0.001). The present study extends the literature by demonstrating a unique, inverse association of brain glycine levels with recent heavy drinking in treatment naïve individuals with AUD. If replicated and extended, these data could lead to enhanced knowledge of how glycinergic systems change with alcohol consumption and AUD progression leading to pharmacological interventional/preventative strategies that modulate brain glycine levels.

Identification and initial validation of empirically derived bipolar symptom states from a large longitudinal dataset: an application of hidden Markov modeling to the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) study

BACKGROUND

Although bipolar disorder (BD) is a fundamentally cyclical illness, a divided model of BD that emphasizes polarity over cyclicity has dominated modern psychiatric diagnostic systems since their advent in the 1980s. However, there has been a gradual return to conceptualizations of BD which focus on longitudinal course in the research community due to emerging supportive data. Advances in longitudinal statistical methods promise to further progress the field.

METHODS

The current study employed hidden Markov modeling to uncover empirically derived manic and depressive states from longitudinal data [i.e. Young Mania Rating Scale and Montgomery-Asberg Depression Rating Scale responses across five occasions from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) study], estimate participants' probabilities of transitioning between these states over time (n = 3918), and evaluate whether clinical variables (e.g. rapid cycling and substance dependence) predict participants' state transitions (n = 3229).

RESULTS

Analyses identified three empirically derived mood states ('euthymic,' 'depressed,' and 'mixed'). Relative to the euthymic and depressed states, the mixed state was less commonly experienced, more temporally unstable, and uniquely associated with rapid cycling, substance use, and psychosis. Individuals assigned to the mixed state at baseline were relatively less likely to be diagnosed with BD-II (v. BD-I), more likely to present with a mixed or (hypo)manic episode, and reported experiencing irritable and elevated mood more frequently.

CONCLUSIONS

The results from the current study represent an important step in defining, and characterizing the longitudinal course of, empirically derived mood states that can be used to form the foundation of objective, empirical attempts to define meaningful subtypes of affective illness defined by clinical course.

Big GABA II: Water-referenced edited MR spectroscopy at 25 research sites

Accurate and reliable quantification of brain metabolites measured in vivo using ¹H magnetic resonance spectroscopy (MRS) is a topic of continued interest. Aside from differences in the basic approach to quantification, the quantification of metabolite data acquired at different sites and on different platforms poses an additional methodological challenge. In this study, spectrally edited γ-aminobutyric acid (GABA) MRS data were analyzed and GABA levels were quantified relative to an internal tissue water reference. Data from 284 volunteers scanned across 25 research sites were collected using GABA+ (GABA + co-edited macromolecules (MM)) and MM-suppressed GABA editing. The unsuppressed water signal from the volume of interest was acquired for concentration referencing. Whole-brain T₁-weighted structural images were acquired and segmented to determine gray matter, white matter and cerebrospinal fluid voxel tissue fractions. Water-referenced GABA measurements were fully corrected for tissue-dependent signal relaxation and water visibility effects. The cohort-wide coefficient of variation was 17% for the GABA + data and 29% for the MM-suppressed GABA data. The mean within-site coefficient of variation was 10% for the GABA + data and 19% for the MM-suppressed GABA data. Vendor differences contributed 53% to the total variance in the GABA + data, while the remaining variance was attributed to site- (11%) and participant-level (36%) effects. For the MM-suppressed data, 54% of the variance was attributed to site differences, while the remaining 46% was attributed to participant differences. Results from an exploratory analysis suggested that the vendor differences were related to the unsuppressed water signal acquisition. Discounting the observed vendor-specific effects, water-referenced GABA measurements exhibit similar levels of variance to creatine-referenced GABA measurements. It is concluded that quantification using internal tissue water referencing is a viable and reliable method for the quantification of in vivo GABA levels.

Brain Glutamate, GABA, and Glutamine Levels and Associations with Recent Drinking in Treatment-Naïve Individuals with Alcohol Use Disorder Versus Light Drinkers

BACKGROUND

Proton magnetic resonance spectroscopy (¹ H-MRS) studies have demonstrated abnormal levels of a variety of neurometabolites in inpatients/outpatients with alcohol use disorder (AUD) following acute alcohol withdrawal relative to healthy controls. In contrast, few studies have compared neurometabolite levels between less severe, treatment-naïve AUD individuals and light drinkers (LD) or related them to recent alcohol consumption. The present study compared neurometabolite levels between treatment-naïve AUD and LD individuals.

METHODS

Twenty treatment-naïve individuals with AUD and 20 demographically matched LD completed an ¹ H-MRS scan, approximately 2.5 days following their last reported drink. ¹ H-MRS data were acquired in dorsal anterior cingulate (dACC) using a 2-dimensional J-resolved point-resolved spectroscopy sequence. dACC neurometabolite levels, with a focus on glutamate, glutamine, and GABA, were compared between AUD and LD participants. The associations between metabolite levels and recent drinking were explored.

RESULTS

AUD participants had significantly lower concentrations of GABA (Cohen's d = 0.79, p = 0.017) and glutamine (Cohen's d = 1.12, p = 0.005), but not glutamate (Cohen's d = 0.05, p = 0.893), relative to LD. As previously reported, AUD participants' glutamate and N-acetylaspartate concentrations were inversely associated with their number of heavy drinking days. In contrast, neither number of drinking (mean p = 0.56) nor heavy drinking (mean p = 0.47) days were associated with metabolite concentrations in LD.

CONCLUSIONS

The present study demonstrated significantly lower levels of prefrontal γ-aminobutyric acid and glutamine in treatment-naïve individuals with AUD relative to LD. Whether these findings reflect the neurotoxic consequence and/or neuroadaptive response of alcohol consumption versus a predrinking trait, and therefore a more durable neurochemical disturbance, awaits elucidation from longitudinal studies.

Two-Dimensional Proton Magnetic Resonance Spectroscopy versus J-Editing for GABA Quantification in Human Brain: Insights from a GABA-Aminotransferase Inhibitor Study

Metabolite-specific, scalar spin-spin coupling constant (J)-editing ¹H MRS methods have become gold-standard for measuring brain γ-amino butyric acid (GABA) levels in human brain. Localized, two-dimensional (2D) ¹H MRS technology offers an attractive alternative as it significantly alleviates the problem of severe metabolite signal overlap associated with standard 1D MRS and retains spectroscopic information for all MRS-detectable species. However, for metabolites found at low concentration, a direct, in vivo, comprehensive methods comparison is challenging and has not been reported to date. Here, we document an assessment of comparability between 2D ¹H MRS and J-editing methods for measuring GABA in human brain. This clinical study is unique in that it involved chronic administration a GABA-amino transferase (AT) inhibitor (CPP-115), which induces substantial increases in brain GABA concentration, with normalization after washout. We report a qualitative and quantitative comparison between these two measurement techniques. In general, GABA concentration changes detected using J-editing were closely mirrored by the 2D ¹H MRS time courses. The data presented are particularly encouraging considering recent 2D ¹H MRS methodological advances are continuing to improve temporal resolution and spatial coverage for achieving whole-brain, multi-metabolite mapping.

Big GABA: Edited MR spectroscopy at 24 research sites

Magnetic resonance spectroscopy (MRS) is the only biomedical imaging method that can noninvasively detect endogenous signals from the neurotransmitter γ-aminobutyric acid (GABA) in the human brain. Its increasing popularity has been aided by improvements in scanner hardware and acquisition methodology, as well as by broader access to pulse sequences that can selectively detect GABA, in particular J-difference spectral editing sequences. Nevertheless, implementations of GABA-edited MRS remain diverse across research sites, making comparisons between studies challenging. This large-scale multi-vendor, multi-site study seeks to better understand the factors that impact measurement outcomes of GABA-edited MRS. An international consortium of 24 research sites was formed. Data from 272 healthy adults were acquired on scanners from the three major MRI vendors and analyzed using the Gannet processing pipeline. MRS data were acquired in the medial parietal lobe with standard GABA+ and macromolecule- (MM-) suppressed GABA editing. The coefficient of variation across the entire cohort was 12% for GABA+ measurements and 28% for MM-suppressed GABA measurements. A multilevel analysis revealed that most of the variance (72%) in the GABA+ data was accounted for by differences between participants within-site, while site-level differences accounted for comparatively more variance (20%) than vendor-level differences (8%). For MM-suppressed GABA data, the variance was distributed equally between site- (50%) and participant-level (50%) differences. The findings show that GABA+ measurements exhibit strong agreement when implemented with a standard protocol. There is, however, increased variability for MM-suppressed GABA measurements that is attributed in part to differences in site-to-site data acquisition. This study's protocol establishes a framework for future methodological standardization of GABA-edited MRS, while the results provide valuable benchmarks for the MRS community.

Unique prefrontal GABA and glutamate disturbances in co-occurring bipolar disorder and alcohol dependence

Bipolar disorder (BD) and alcohol dependence (AD) frequently co-occur, and co-occurring BD and AD are associated with devastating public health costs. Minimal neurobiological research exists to guide the development of effective treatments for this treatment-resistant population. We believe the present study represents the first investigation of prefrontal gamma-aminobutyric acid (GABA) and glutamate levels in co-occurring BD and current AD. The participants were 78 individuals who met DSM-IV criteria for BD I/II and current AD (n=20), BD I/II alone (n=19), current AD alone (n=20) or no diagnosis (n=19). The participants completed a baseline diagnostic visit, then returned approximately 4 days later for a two-dimensional J-resolved proton magnetic resonance spectroscopy (¹H-MRS) acquisition in dorsal anterior cingulate cortex (dACC). All participants were required to demonstrate ⩾1 week of abstinence from alcohol/drugs via serial biomarker testing before ¹H-MRS. A 2 × 2 factorial analysis of variance of cerebrospinal fluid (CSF)-corrected GABA/water concentrations demonstrated a significant BD × AD interaction (F=2.91, P<0.05), signifying uniquely low levels of GABA in BD+AD; this effect doubled when the sample was restricted to individuals who consumed alcohol within 2 weeks of ¹H-MRS. There were no overall effects of BD/AD on CSF-corrected glutamate/water levels. However, the BD × AD interaction, signifying uniquely low levels of glutamate in BD+AD, approached statistical significance (F=3.83, P=0.06) in individuals who consumed alcohol within 2 weeks of ¹H-MRS. The dACC GABA levels were significantly, negatively associated with Barratt Impulsiveness Scale (r=-0.28, P=0.02) and Obsessive Compulsive Drinking Scale (r=-0.35, P<0.01) scores. If replicated, these results may suggest that future treatment studies should preferentially evaluate therapeutics in BD+AD known to increase prefrontal GABA and glutamate levels.

An item response theory evaluation of the young mania rating scale and the montgomery-asberg depression rating scale in the systematic treatment enhancement program for bipolar disorder (STEP-BD)

BACKGROUND

The Young Mania Rating Scale (YMRS) and Montgomery-Asberg Depression Rating Scale (MADRS) are among the most widely used outcome measures for clinical trials of medications for Bipolar Disorder (BD). Nonetheless, very few studies have examined the measurement characteristics of the YMRS and MADRS in individuals with BD using modern psychometric methods. The present study evaluated the YMRS and MADRS in the Systematic Treatment Enhancement Program for BD (STEP-BD) study using Item Response Theory (IRT).

METHODS

Baseline data from 3716 STEP-BD participants were available for the present analysis. The Graded Response Model (GRM) was fit separately to YMRS and MADRS item responses. Differential item functioning (DIF) was examined by regressing a variety of clinically relevant covariates (e.g., sex, substance dependence) on all test items and on the latent symptom severity dimension, within each scale.

RESULTS

Both scales: 1) contained several items that provided little or no psychometric information, 2) were inefficient, in that the majority of item response categories did not provide incremental psychometric information, 3) poorly measured participants outside of a narrow band of severity, 4) evidenced DIF for nearly all items, suggesting that item responses were, in part, determined by factors other than symptom severity.

LIMITATIONS

Limited to outpatients; DIF analysis only sensitive to certain forms of DIF.

CONCLUSIONS

The present study provides evidence for significant measurement problems involving the YMRS and MADRS. More work is needed to refine these measures and/or develop suitable alternative measures of BD symptomatology for clinical trials research.

Alcohol-Induced Stimulation Mediates the Effect of a GABRA2 SNP on Alcohol Self-Administrated among Alcohol-Dependent Individuals

BACKGROUND

A single-nucleotide polymorphism (SNP) in GABRA2 (rs279858) may moderate subjective response (SR) to alcohol. Results of studies in non-dependent drinkers examining this GABRA2 SNP on SR have been equivocal. This study examined this SNP's direct and indirect effects on alcohol self-administration in dependent drinkers.

METHOD

The sample consisted of 63 Caucasian, non-treatment-seeking individuals with alcohol dependence. Subjective stimulation was assessed using the Biphasic Alcohol Effects Scale following consumption of an alcoholic priming drink (target breath alcohol content = 0.02 g%). Participants were subsequently offered the opportunity to self-administer up to eight additional drinks.

RESULTS

Controlling for baseline stimulation, T-allele homozygotes, relative to individuals with at least one copy of the C-allele, reported greater initial stimulation, t(58) = 2.011, p = 0.049. Greater stimulation predicted greater subsequent alcohol self-administration, t(57) = 2.522, p = 0.015. Although rs279858 genotype did not directly impact self-administration (t(57) = -0.674, p = 0.503), it did have an indirect effect (95% confidence interval [0.068, 1.576]), such that T-allele homozygotes reported greater stimulation, which in turn predicted greater self-administration.

CONCLUSION

These results suggest that the influence of this SNP on SR differs depending on dose or stage of dependence. This study is the first to demonstrate an indirect effect of rs279858 genotype on drinking through SR. Although C-allele carriers have been shown to have an increased risk for alcohol dependence, in our dependent sample, greater stimulation was found among T-allele homozygotes, suggesting that the influence of SR on developing and maintaining dependence differs based on rs279858 genotype.This study demonstrates an indirect effect of rs279858 genotype on drinking through SR. Although C-allele carriers have an increased risk for alcohol dependence, in our dependent sample, greater stimulation was found among T-allele homozygotes, suggesting that the influence of SR on developing dependence differs based on rs279858 genotype.

Associations Between Recent Heavy Drinking and Dorsal Anterior Cingulate N-Acetylaspartate and Glutamate Concentrations in Non-Treatment-Seeking Individuals with Alcohol Dependence

BACKGROUND

Proton magnetic resonance spectroscopy ((1) H-MRS) studies have consistently found abnormal brain concentrations of N-acetylaspartate (NAA) and glutamate in individuals with alcohol use disorders (AUD) relative to light drinkers. However, most such studies have focused on individuals in treatment for severe alcohol dependence (AD), and few studies have investigated associations between neurochemical concentrations and recent alcohol consumption. This study focused on associations between recent drinking and prefrontal neurometabolite concentrations in nonsevere, non-treatment-seeking individuals with AUD.

METHODS

Nineteen treatment-naïve alcohol-dependent individuals aged 21 to 40 completed a (1) H-MRS scan. Single-voxel (1) H-MRS spectra were acquired in dorsal anterior cingulate cortex (dACC) using a 2-dimensional J-resolved point resolved spectroscopy sequence. Associations between recent heavy drinking, assessed using the Timeline FollowBack, and dACC metabolite concentrations were estimated via regression controlling for within-voxel tissue composition.

RESULTS

Participants provided a negative breathalyzer reading and reported between 1 and 5 days (M = 2.45, SD = 1.23) since their last drink. Number of heavy drinking days in the 14 days preceding the scan (M = 4.84, SD = 3.32) was significantly inversely associated with both glutamate/water (β = -0.63, t(17) = -3.37, p = 0.004) and NAA/water concentrations (β = -0.59, t(17) = -2.98, p = 0.008).

CONCLUSIONS

This study extends the literature by demonstrating inverse associations between recent heavy drinking and dACC glutamate and NAA concentrations in a sample of nonsevere, non-treatment-seeking individuals with AD. These findings may support the hypothesis that amount of recent alcohol consumption may account for differences in neuronal metabolism, even in nonsevere, non-treatment-seeking alcoholics.

Individualized real-time fMRI neurofeedback to attenuate craving in nicotine-dependent smokers

BACKGROUND

Cue-induced craving plays an important role in relapse, and the neural correlates of cue-induced craving have been elucidated using fMRI. This study examined the utility of real-time fMRI (rtfMRI) neurofeedback to strengthen self-regulation of craving-related neural activation and cue-reactivity in cigarette smokers.

METHODS

Nicotine-dependent smokers were randomized to rtfMRI neurofeedback or to a no-feedback control group. Participants completed 3 neuroimaging visits. Within each visit, an initial run during which smoking-related cues were used to provoke craving, an individualized craving-related region of interest (ROI) in the prefrontal cortex or anterior cingulate cortex was identified. In the rtfMRI group, activity from the ROI was fed back via a visual display during 3 subsequent runs while participants were instructed to reduce craving during cue exposure. The control group had an identical experience with no feedback provided.

RESULTS

Forty-four nicotine-dependent smokers were recruited to participate in our study; data from the 33 participants who completed a 1-week follow-up visit were included in the analysis. Subjective craving ratings and cue-induced brain activation were lower in the rtfMRI group than in the control group.

LIMITATIONS

As participants were not seeking treatment, clinical outcomes are lacking.

CONCLUSION

Nicotine-dependent smokers receiving rtfMRI feedback from an individualized ROI attenuated smoking cue-elicited neural activation and craving, relative to a control group. Further studies are needed in treatment-seeking smokers to determine if this intervention can translate into a clinically meaningful treatment modality.

Evidence for the continuous latent structure of mania and depression in out-patients with bipolar disorder: results from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD)

BACKGROUND

Evidence supporting the continuous latent structure of mood phenomena has not been incorporated into psychiatric diagnostic systems, in part because the evidence has been incomplete. For example, no studies have investigated the boundary between 'sick' and 'well' periods in individuals with bipolar disorder, despite agreement that characterization of mood disorders as having a discrete episodic course is inaccurate. The present study examined the validity of mood episode symptom thresholds in out-patients with bipolar disorder using multiple methodologies: taxometrics and information-theoretic latent distribution modeling (ITLDM), to evaluate the continuity/discontinuity of mood symptoms; and structural equation mixture modeling (SEMM), to evaluate the continuity/discontinuity of associations between mood symptoms and general functioning.

METHOD

A total of 3721 out-patients with bipolar disorder from the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) were available for analysis. Data were collected at participants' baseline STEP-BD visit. Taxometric [maximum covariance/means above minus below a cut (MAXCOV/MAMBAC) with simulated comparison data], ITLDM and SEMM methods were applied twice, once to the Montgomery-Åsberg Depression Rating Scale and again to the Young Mania Rating Scale.

RESULTS

Taxometric results unequivocally supported a continuous interpretation of the data. ITLDM results favored many valued 'discrete metrical' models, suggesting that mood symptoms have continuous, but potentially non-normally distributed, latent structures in out-patients with bipolar disorder. Finally, SEMM results demonstrated that latent associations between mood symptoms and general functioning were linear.

CONCLUSIONS

Results from the present study argue against the validity of DSM mood episode thresholds and argue for a graded continuum of care of bipolar symptom management.

D-cycloserine combined with cue exposure therapy fails to attenuate subjective and physiological craving in cocaine dependence

BACKGROUND

Based on preclinical studies showing that the partial N-methyl-D-aspartate (NMDA) agonist D-cycloserine (DCS) facilitates extinction of cocaine self-administration and cocaine-induced conditioned place preference, we evaluated whether 50 mg of DCS would reduce craving to cocaine cues when combined with cue exposure (CE) in cocaine dependent humans.

METHODS

In this double-blind placebo-controlled pilot study, 47 cocaine dependent participants were randomized to DCS or placebo (PBO), plus CE. Participants received DCS or PBO 30 minutes prior to two CE sessions, conducted one day apart. Craving and heart rate was assessed prior to CE sessions, during CE trials, and after CE trials. These measures were assessed again at a 1-week follow-up (session 3) after the second CE session.

RESULTS

DCS failed to significantly attenuate cocaine cue reactivity based on subjective craving and physiological reactivity (heart rate) compared to PBO. The CE protocol, consisting of repeated exposure to drug cues combined with skills training, resulted in extinction to cocaine cues as suggested by decreased craving within and between sessions in both treatment conditions. All participants exhibited elevated heart rate with repeated exposures, demonstrating a potentiation in heart rate between sessions.

CONCLUSIONS

50 mg of DCS may not be effective for extinguishing reactivity to drug cues for individuals with cocaine dependence.

SCIENTIFIC SIGNIFICANCE

Future studies examining the effect of DCS on facilitating extinction to drug cues should examine variations in cue exposure length, number of CE presentations, and timing of DCS dose administration prior to cue exposures, which may differentially impact drug cue reactivity.

The relationship between years of cocaine use and brain activation to cocaine and response inhibition cues

AIMS

Functional magnetic resonance imaging research has attempted to elucidate the neurobehavioral underpinnings of cocaine dependence by evaluating differences in brain activation to cocaine and response inhibition cues between cocaine-dependent individuals and controls. This study investigated associations between task-related brain activation and cocaine use characteristics.

DESIGN

Cross-sectional.

SETTING

The Center for Biomedical Imaging at the Medical University of South Carolina, USA.

PARTICIPANTS

Fifty-one cocaine users (41 dependent).

MEASUREMENTS

Brain activation to cocaine-cue exposure and Go No-Go tasks in six a priori selected brain regions of interest and cocaine use characteristics (i.e. cocaine dependence status, years of cocaine use, cocaine use in the past 90 days) assessed via standardized interviews.

FINDINGS

Participants demonstrated elevated activation to cocaine (bilateral ventral striatum, dorsal caudate, amygdala) and response inhibition (bilateral anterior cingulate, insula, inferior frontal gyrus) cues in all hypothesized brain regions. Years of cocaine use was associated with task-related brain activation, with more years of cocaine use associated with greater activation to cocaine cues in right (F = 7.97, P = 0.01) and left (F = 5.47, P = 0.02) ventral striatum and greater activation to response inhibition cues in left insula (F = 5.10, P = 0.03) and inferior frontal gyrus (F = 4.12, P = 0.05) controlling for age, cocaine dependence status and cocaine use in the past 90 days.

CONCLUSIONS

Years of cocaine use may be more centrally related to cocaine cue and response inhibition brain activation than cocaine dependence diagnosis or amount of recent use.

Brain activation to cocaine cues and motivation/treatment status

Motivation to change is believed to be a key factor in therapeutic success in substance use disorders; however, the neurobiological mechanisms through which motivation to change impacts decreased substance use remain unclear. Existing research is conflicting, with some investigations supporting decreased and others reporting increased frontal activation to drug cues in individuals seeking treatment for substance use disorders. The present study investigated the relationship between motivation to change cocaine use and cue-elicited brain activity in cocaine-dependent individuals using two conceptualizations of 'motivation to change': (1) current treatment status (i.e. currently receiving versus not receiving outpatient treatment for cocaine dependence) and (2) self-reported motivation to change substance use, using the Stages of Change Readiness and Treatment Eagerness Scale. Thirty-eight cocaine-dependent individuals (14 currently in treatment) completed a diagnostic assessment and an fMRI cocaine cue-reactivity task. Whole-brain analyses demonstrated that both treatment-seeking and motivated participants had lower activation to cocaine cues in a wide variety of brain regions in the frontal, occipital, temporal and cingulate cortices relative to non-treatment-seeking and less motivated participants. Future research is needed to explain the mechanism by which treatment and/or motivation impacts neural cue reactivity, as such work could potentially aid in the development of more effective therapeutic techniques for substance-dependent patients.

Impact of DCS-facilitated cue exposure therapy on brain activation to cocaine cues in cocaine dependence

BACKGROUND

The development of addiction is marked by a pathological associative learning process that imbues incentive salience to stimuli associated with drug use. Recent efforts to treat addiction have targeted this learning process using cue exposure therapy augmented with d-cycloserine (DCS), a glutamatergic agent hypothesized to enhance extinction learning. To better understand the impact of DCS-facilitated extinction on neural reactivity to drug cues, the present study reports fMRI findings from a randomized, double-blind, placebo-controlled trial of DCS-facilitated cue exposure for cocaine dependence.

METHODS

Twenty-five participants completed two MRI sessions (before and after intervention), with a cocaine-cue reactivity fMRI task. The intervention consisted of 50mg of DCS or placebo, combined with two sessions of cocaine cue exposure and skills training.

RESULTS

Participants demonstrated cocaine cue activation in a variety of brain regions at baseline. From the pre- to post-study scan, participants experienced decreased activation to cues in a number of regions (e.g., accumbens, caudate, frontal poles). Unexpectedly, placebo participants experienced decreases in activation to cues in the left angular and middle temporal gyri and the lateral occipital cortex, while DCS participants did not.

CONCLUSIONS

Three trials of DCS-facilitated cue exposure therapy for cocaine dependence have found that DCS either increases or does not significantly impact response to cocaine cues. The present study adds to this literature by demonstrating that DCS may prevent extinction to cocaine cues in temporal and occipital brain regions. Although consistent with past research, results from the present study should be considered preliminary until replicated in larger samples.

Modeling longitudinal drinking data in clinical trials: an application to the COMBINE study

BACKGROUND

There is a lack of consensus in the literature as to how to define drinking outcomes in clinical trials. Typically, separate statistical models are fit to assess treatment effects on several summary drinking measures. These summary measures do not capture the complexity of drinking behavior. We used the COMBINE study to illustrate a statistical approach for examining treatment effects on high-resolution drinking data.

METHODS

This is a secondary data analysis of COMBINE participants randomly assigned to naltrexone, acamprosate, with medical management and/or combined behavioral intervention (CBI). Using a Poisson hurdle model, abstinence and number of drinks were simultaneously modeled as a function of treatment and covariates. An emphasis was placed on the evaluation of "risky drinking" (3 drinks/day for women and 4 for men).

RESULTS

During treatment, naltrexone increased the odds of abstinence vs placebo naltrexone (OR=1.35 [1.06, 1.65]) but receiving CBI in addition to naltrexone (vs not) obscured this effect; thus, the naltrexone effect was largest in the group not receiving CBI (OR=1.87 [1.29, 2.46]). Naltrexone vs placebo naltrexone also reduced the risk of drinking in those who resumed risky drinking (RR=0.58 [0.24, 0.93]) and increased the odds of maintaining low risk drinking (OT=1.99 [1.07, 2.90]). Both effects were strongest in the absence of CBI when only "medical management" was provided.

CONCLUSIONS

The hurdle model is an appropriate statistical tool for assessing the effect of treatment on the two part drinking process, abstinence and number of drinks. When applied to COMBINE, results bolster the use of naltrexone in promoting abstinence and reduction in risky drinking.

Sustained reduction of nicotine craving with real-time neurofeedback: exploring the role of severity of dependence

BACKGROUND

Neurofeedback delivered via real-time functional magnetic resonance imaging (rtfMRI) is a promising therapeutic technique being explored to facilitate self-regulation of craving in nicotine-dependent cigarette smokers. The current study examined the role of nicotine-dependence severity and the efficacy of multiple visits of neurofeedback from a single region of interest (ROI) in the anterior cingulate cortex (ACC) on craving reduction.

METHODS

Nine nicotine-dependent cigarette smokers participated in three rtfMRI visits that examined cue-induced craving and brain activation. Severity of nicotine dependence was assessed with the Fagerström Test for Nicotine Dependence. When viewing smoking-related images with instructions to "crave," patient-tailored ROIs were generated in the vicinity of the ACC. Activity levels from the ROI were fed back while participants viewed smoking cues with the instruction to reduce craving.

RESULTS

Neurofeedback from a single ROI in the ACC led to consistent decreases in self-reported craving and activation in the ACC across the three visits. Dependence severity predicted response to neurofeedback at Visit 3.

CONCLUSIONS

This study builds upon previous rtfMRI studies on the regulation of nicotine craving in demonstrating that feedback from the ACC can reduce activation to smoking cues across three separate visits. Individuals with lower nicotine-dependence severity were more successful in reducing ACC activation over time. These data highlight the need to consider dependence severity in developing more individualized neurofeedback methods.

Reduction of cue-induced craving through realtime neurofeedback in nicotine users: the role of region of interest selection and multiple visits

This multi-visit, real-time functional magnetic resonance imaging feedback study demonstrates that treatment-seeking smokers can effectively modulate their behavioral and brain responses to smoking cues. They are more effective at decreasing activity in functionally defined regions involved in "craving" (e.g. ventral anterior cingulate cortex (vACC)) rather than increasing activity in regions involved in "resisting" (e.g. dorsal medial prefrontal cortex (dmPFC)).

Prospective associations between brain activation to cocaine and no-go cues and cocaine relapse

BACKGROUND

The ability to predict potential for relapse to substance use following treatment could be very useful in targeting aftercare strategies. Recently, a number of investigators have focused on using neural activity measured by fMRI to predict relapse propensity. The purpose of the present study was to use fMRI to investigate prospective associations between brain reactivity to cocaine and response inhibition cues and relapse to cocaine use.

METHODS

Thirty cocaine-dependent participants with clean cocaine urine drug screens (UDS) completed a baseline fMRI scan, including a cocaine-cue reactivity task and a go no-go response inhibition task. After participating in a brief clinical trial of d-cycloserine for the facilitation of cocaine-cue extinction, they returned for a one-week follow-up UDS. Associations between baseline activation to cocaine and inhibition cues and relapse to cocaine use were explored.

RESULTS

Positive cocaine UDS was significantly associated with cocaine-cue activation in the right putamen and insula, as well as bilateral occipital regions. Associations between positive cocaine UDS and activation to no-go cues were concentrated in the postcentral gyri, a region involved in response execution.

CONCLUSIONS

Although preliminary, these results suggest that brain imaging may be a useful tool for predicting risk for relapse in cocaine-dependent individuals. Further, larger-scale naturalistic studies are needed to corroborate and extend these findings.

Volitional reduction of anterior cingulate cortex activity produces decreased cue craving in smoking cessation: a preliminary real-time fMRI study

Numerous research groups are now using analysis of blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) results and relaying back information about regional activity in their brains to participants in the scanner in 'real time'. In this study, we explored the feasibility of self-regulation of frontal cortical activation using real-time fMRI (rtfMRI) neurofeedback in nicotine-dependent cigarette smokers during exposure to smoking cues. Ten cigarette smokers were shown smoking-related visual cues in a 3 Tesla MRI scanner to induce their nicotine craving. Participants were instructed to modify their craving using rtfMRI feedback with two different approaches. In a 'reduce craving' paradigm, participants were instructed to 'reduce' their craving, and decrease the anterior cingulate cortex (ACC) activity. In a separate 'increase resistance' paradigm, participants were asked to increase their resistance to craving and to increase middle prefrontal cortex (mPFC) activity. We found that participants were able to significantly reduce the BOLD signal in the ACC during the 'reduce craving' task (P=0.028). There was a significant correlation between decreased ACC activation and reduced craving ratings during the 'reduce craving' session (P=0.011). In contrast, there was no modulation of the BOLD signal in mPFC during the 'increase resistance' session. These preliminary results suggest that some smokers may be able to use neurofeedback via rtfMRI to voluntarily regulate ACC activation and temporarily reduce smoking cue-induced craving. Further research is needed to determine the optimal parameters of neurofeedback rtfMRI, and whether it might eventually become a therapeutic tool for nicotine dependence.

The primary health care version of ICD-11: the detection of common mental disorders in general medical settings

BACKGROUND

The primary health care version of the ICD-11 is currently being revised.

AIM

To test two brief sets of symptoms for depression and anxiety in primary care settings, and validate them against diagnoses of major depression and current generalised anxiety made by the CIDI.

METHOD

The study took place in general medical or primary care clinics in 14 different countries, using the Composite International Diagnostic Interview adapted for primary care (CIDI-PC) in 5,438 patients. The latent structure of common symptoms was explored, and two symptom scales were derived from item response theory (IRT), these were then investigated against research diagnoses.

RESULTS

Correlations between dimensions of anxious, depressive and somatic symptoms were found to be high. For major depression the 5 item depression scale has marked superiority over the usual 2 item scales used by both the ICD and DSM systems, and for anxiety there is some superiority. If the questions are used with patients that the clinician suspects may have a psychological disorder, the positive predictive value of the scale is between 78 and 90%.

CONCLUSION

The two scales allow clinicians to make diagnostic assessments of depression and anxiety with a high positive predictive value, provided they use them only when they suspect that a psychological disorder is present.

Associations between behavioral disinhibition and cocaine use history in individuals with cocaine dependence

BACKGROUND

Behavioral disinhibition has been suggested as both a cause and consequence of substance use disorders. Many studies examining associations between behavioral disinhibition and substance use history have focused on individuals with alcohol dependence or non-dependent college students. In the present study, the relationship between behavioral disinhibition and cocaine use history in individuals with cocaine dependence is examined.

METHODS

Forty-six non-treatment-seeking cocaine-dependent men and women completed impulsivity (Barratt impulsiveness scale; BIS) and novelty seeking (temperament and character inventory; TCI) questionnaires at the baseline visit of an ongoing study. Unadjusted, and adjusted for gender and age, Pearson correlations were calculated between BIS, TCI, and cocaine use variables from the structured clinical interview for DSM-IV and timeline follow-back (age of onset, quantity/frequency of past 30 day cocaine use).

RESULTS

As expected, elevated motor impulsivity and novelty seeking were each associated with younger age of dependence onset. Also, individuals with lower levels of persistence on the TCI reported more days of cocaine use over the previous month. Unexpectedly, increased novelty seeking and attentional impulsivity were associated with fewer days of cocaine use and less money spent on cocaine, respectively. Controlling for age and gender did not substantially change the pattern of observed associations.

CONCLUSIONS

The present study provides preliminary evidence for associations between behavioral disinhibition and cocaine use history in cocaine-dependent individuals. Given our relatively small sample size and the correlational nature of our findings, further research is needed to replicate and extend our results.

Real-time fMRI in the treatment of nicotine dependence: a conceptual review and pilot studies

Technical advances allowing for the analysis of functional MRI (fMRI) results in real time have led to studies exploring the ability of individuals to use neural feedback signals to modify behavior and regional brain activation. The use of real-time fMRI (rtfMRI) feedback has been explored for therapeutic benefit in a number of disease states, but to our knowledge, the potential therapeutic benefit of rtfMRI feedback in the treatment of addictive disorders has not been explored. This article will provide an overview of the development of rtfMRI and discussion of its potential uses in the treatment of addictions. We also describe a series of pilot studies that highlight some of the technical challenges in developing a rtfMRI feedback paradigm for use in addictions, specifically in nicotine dependence. Because the use of rtfMRI feedback is in its infancy, the work described is focused on establishing some of the basic parameters in optimizing the rtfMRI feedback, such as the type of feedback signal, region of interest for feedback and predicting which subjects are most likely to respond well to training. While rtfMRI feedback remains an intriguing possibility for the treatment of addictions, much work remains to be done in establishing its efficacy.

Simultaneous modeling of the impact of treatments on alcohol consumption and quality of life in the COMBINE study: a coupled hidden Markov analysis

BACKGROUND

Clinical trials for alcoholism have historically regarded alcohol consumption as the primary outcome. In a subset of trials, quality of life (QOL) has been considered as a secondary outcome. Joint latent-variable modeling techniques may provide a more accurate and powerful simultaneous analysis of primary and secondary outcomes in clinical trials. The goal of this study was to evaluate longitudinal associations between treatment status, alcohol consumption, and QOL in the Combined Pharmacotherapies and Behavioral Interventions for Alcohol Dependence (COMBINE) study.

METHODS

A total of 1,383 alcohol-dependent patients were randomized to 9 treatment groups. Percent heavy drinking days (PHDD) and health-related QOL from the 30 days preceding baseline, week 16, and week 52 were calculated using the Form 90 and the Medical Outcomes Study Health Survey Short Form-12 (SF-12), respectively. Latent profile analysis (LPA) was conducted to determine an appropriate number of latent states to represent PHDD and QOL. Subsequently, univariate and coupled hidden Markov models (for PHDD and SF-12 mental health, and PHDD and SF-12 physical) were fit to the data.

RESULTS

LPA suggested that PHDD should be represented by 3 latent states and that each SF-12 scale should be represented by 2 states. Joint modeling results suggested that (i) naltrexone significantly predicted decreased PHDD (p < 0.05), and marginally predicted improved mental health QOL via decreased PHDD (p < 0.10), and (ii) that the combinations of naltrexone and combined behavioral intervention (CBI), and acamprosate and CBI, each predicted significantly improved physical QOL (p < 0.05), and marginally predicted decreased PHDD via improved physical QOL (p < 0.10).

CONCLUSIONS

This study illustrates a powerful and novel statistical approach for simultaneously evaluating the impact of treatments on primary and secondary outcomes in clinical trials. This study also suggests that behavioral interventions may impact drinking behavior through their ameliorative effects on QOL.

A randomized, double-blind, placebo-controlled clinical trial of acamprosate in alcohol-dependent individuals with bipolar disorder: a preliminary report

BACKGROUND

Alcohol use disorders commonly co-occur with bipolar disorder and are associated with a more severe course of bipolar illness, yet treatment research in this important clinical population is scarce. The current study assessed the effects of acamprosate on alcohol use and mood symptoms in subjects with co-occurring bipolar disorder and active alcohol dependence.

METHODS

Thirty-three adults meeting criteria for bipolar I or bipolar II disorder and current alcohol dependence were randomized to receive add-on acamprosate (1998 mg/day) or placebo while concurrently maintained on mood stabilizing medications. Participants were assessed weekly for frequency and quantity of alcohol consumption and general clinical severity for eight weeks. Depressive symptoms, manic symptoms, and alcohol craving were assessed biweekly. Biomarkers of alcohol use were assessed at study baseline and endpoint.

RESULTS

Of the 33 subjects randomized, 23 (69.7%) completed all active phase visits. Over the trial as a whole, no statistically significant treatment differences were detected in drinking outcomes. Post-hoc analysis revealed lower Clinical Global Impression scores of substance use severity in acamprosate-treated participants in weeks 7-8 of the trial. No significant differences in depressive symptoms, manic symptoms, or adverse events were observed between groups.

CONCLUSIONS

Acamprosate was well-tolerated, with no worsening of depressive or manic symptoms, and appeared to confer some clinical benefit in study completers in the last two weeks of the trial. Larger studies of longer duration are required to fully explore the utility of acamprosate in this population.

The structure of depression, anxiety and somatic symptoms in primary care

BACKGROUND

Observed co-morbidity among the mood and anxiety disorders has led to the development of increasingly sophisticated dimensional models to represent the common and unique features of these disorders. Patients often present to primary care settings with a complex mixture of anxiety, depression and somatic symptoms. However, relatively little is known about how somatic symptoms fit into existing dimensional models.

METHOD

We examined the structure of 91 anxiety, depression and somatic symptoms in a sample of 5433 primary care patients drawn from 14 countries. One-, two- and three-factor lower-order models were considered; higher-order and hierarchical variants were studied for the best-fitting lower-order model.

RESULTS

A hierarchical, bifactor model with all symptoms loading simultaneously on a general factor, along with one of three specific anxiety, depression and somatic factors, was the best-fitting model. The general factor accounted for the bulk of symptom variance and was associated with psychosocial dysfunction. Specific depression and somatic symptom factors accounted for meaningful incremental variance in diagnosis and dysfunction, whereas anxiety variance was associated primarily with the general factor.

CONCLUSIONS

The results (a) are consistent with previous studies showing the presence and importance of a broad internalizing or distress factor linking diverse emotional disorders, and (b) extend the bounds of internalizing to include somatic complaints with non-physical etiologies.

Predictors of clinical trial dropout in individuals with co-occurring bipolar disorder and alcohol dependence

BACKGROUND

Individuals with co-occurring bipolar disorder and alcohol dependence have particularly low rates of retention in clinical trials. Past research has identified a variety of factors associated with dropout in this population, but few have been replicated. The present study investigated the ability of several baseline variables to predict clinical trial dropout in a sample of individuals with co-morbid bipolar and alcohol use disorders.

METHODS

Demographics, psychiatric diagnoses, recent alcohol use, mood pathology, and risk taking behavior (measured with the Balloon Analogue Risk Task) were evaluated as predictors of dropout from a randomized clinical trial of acamprosate for individuals with co-morbid bipolar and alcohol use disorders (n=30) using stepwise logistic regression.

RESULTS

Risk taking behavior was the only significant predictor of dropout in the present study (OR=1.44, p=0.03); opiate dependence marginally predicted dropout as well (OR=13.46, p=0.08). A model consisting of these predictors, as well as acamprosate group status (p=0.13), provided excellent prediction of dropout (i.e., area under the ROC curve=0.94; R(2)=0.53).

CONCLUSIONS

Given the robust relationship between risk taking and dropout in the present study, the Balloon Analogue Risk Task may represent a valuable tool for researchers to predict who will drop out of clinical trials for comorbid bipolar and substance use disorders.

Impact of depressive symptoms on future alcohol use in patients with co-occurring bipolar disorder and alcohol dependence: a prospective analysis in an 8-week randomized controlled trial of acamprosate

BACKGROUND

Bipolar disorders and alcohol use disorders commonly co-occur, yet little is known about the proximal impact of bipolar symptoms on alcohol use in patients with this comorbidity. The present study examined the impact of depressive symptoms and alcohol craving on proximal alcohol use in patients with co-occurring bipolar disorder and alcohol dependence.

METHODS

Data were collected during an 8-week randomized controlled trial of acamprosate for individuals with co-occurring bipolar disorder and alcohol dependence (n = 30). Depressive symptoms and alcohol craving were assessed biweekly using the Montgomery Asberg Depression Rating Scale (MADRS) and the Obsessive Compulsive Drinking Scale (OCDS), respectively. Daily alcohol use data were available via administration of the Time-line Follow-back interview at baseline and at subsequent weekly study visits. Correlational analyses and hidden Markov modeling were used to examine the prospective relationships between depressive symptoms, alcohol craving, and alcohol use.

RESULTS

Depressive symptoms and alcohol craving were significantly correlated with proximal (i.e., 1 week later) alcohol use across a variety of alcohol consumption summary measures. In hidden Markov models, depressive symptoms (OR = 1.3, 95% credible interval = [1.1, 1.5]) and alcohol craving (OR = 1.6, 95% credible interval = [1.4, 1.9]) significantly predicted transitioning from a light to a heavy drinking state, or remaining in a heavy drinking state.

CONCLUSIONS

The results from the present study suggest that depressive symptoms and alcohol craving increase proximal risk for alcohol use in individuals with co-occurring bipolar and alcohol use disorders.

Psychoticism and neuroticism predict cocaine dependence and future cocaine use via different mechanisms

BACKGROUND

Personality characteristics have been associated with cocaine use. However, little is known about the mechanisms through which personality could impact drug use. The present study investigated the cross-sectional and prospective relationships between personality dimensions (i.e., impulsivity, neuroticism) and problematic cocaine use. Reactivity to a pharmacological stressor as a potential mediator of the relationship between neuroticism and future cocaine use was also examined.

METHODS

Participants were 53 cocaine-dependent individuals and 47 non-dependent controls. Subjects completed the Eysenck Personality Questionnaire (EPQ) at baseline and were administered i.v. corticotrophin releasing hormone (CRH; 1 μg/kg). Cocaine use in the 30 days following CRH administration was measured.

RESULTS

Cocaine-dependent individuals had higher scores on the psychoticism (i.e., impulsivity, aggression; p=0.02) and neuroticism (p<0.01) scales of the EPQ than non-dependent controls. Cocaine-dependent individuals also had a greater subjective stress response to CRH than controls (p<0.01). Cocaine-dependent individuals with elevated psychoticism used significantly more cocaine over the follow-up period (p<0.05), whereas individuals with elevated neuroticism trended towards using cocaine more frequently over the follow-up (p=0.07). Finally, there was a trend for an indirect effect of neuroticism on frequency of cocaine use through subjective reactivity to CRH.

CONCLUSIONS

The findings extend past research on the association between personality and cocaine use, and suggest that motives for cocaine use may systematically vary across personality characteristics. Moreover, tailoring therapeutic interventions to individuals' personalities may be an area that warrants further investigation.

Evidence for the continuous latent structure of mania in the Epidemiologic Catchment Area from multiple latent structure and construct validation methodologies

BACKGROUND

Although psychiatric diagnostic systems have conceptualized mania as a discrete phenomenon, appropriate latent structure investigations testing this conceptualization are lacking. In contrast to these diagnostic systems, several influential theories of mania have suggested a continuous conceptualization. The present study examined whether mania has a continuous or discrete latent structure using a comprehensive approach including taxometric, information-theoretic latent distribution modeling (ITLDM) and predictive validity methodologies in the Epidemiologic Catchment Area (ECA) study.

METHOD

Eight dichotomous manic symptom items were submitted to a variety of latent structural analyses, including factor analyses, taxometric procedures and ITLDM, in 10105 ECA community participants. In addition, a variety of continuous and discrete models of mania were compared in terms of their relative abilities to predict outcomes (i.e. health service utilization, internalizing and externalizing disorders, and suicidal behavior).

RESULTS

Taxometric and ITLDM analyses consistently supported a continuous conceptualization of mania. In ITLDM analyses, a continuous model of mania demonstrated 6.52:1 odds over the best-fitting latent class model (LCM) of mania. Factor analyses suggested that the continuous structure of mania was best represented by a single latent factor. Predictive validity analyses demonstrated a consistent superior ability of continuous models of mania relative to discrete models.

CONCLUSIONS

The present study provided three independent lines of support for a continuous conceptualization of mania. The implications of a continuous model of mania are discussed.

Impact of psychiatric comorbidity on mortality in veterans with type 2 diabetes

BACKGROUND

particular psychiatric disorders, such as depression, have a significant and negative effect on diabetes outcomes. However, we know very little about the impact of other psychiatric disorders, and of the effect of multiple psychiatric comorbidities, on the clinical course of diabetes. As such, the present study examined the impact of a wide range of psychiatric comorbidities on all-cause mortality in individuals with type 2 diabetes.

METHODS

retrospective follow-up was conducted of 15,065 veterans with type 2 diabetes enrolled in hospital care between 1997 and 2006. Clinical diagnoses from patient records were used to construct four psychiatric disorder scales: internalizing (i.e., depression and anxiety); externalizing (i.e., alcohol and drug abuse); psychotic; and bipolar. Longitudinal relationships were examined between these scales and mortality using Cox regression.

RESULTS

only externalizing disorders were significantly associated with mortality: hazard ratio = 1.22 (95% confidence interval = 1.02-1.47). In other words, each additional diagnosed externalizing disorder increased an individual's chance of dying over the follow-up period by 22%. This association remained significant when demographics and medical comorbidities were statistically controlled, but was rendered nonsignificant when medication adherence was introduced to the regression model.

CONCLUSIONS

the results provide evidence that among individuals with diabetes, alcohol and drug abuse/dependence have a significant impact on mortality. This increased risk of mortality may have been due to the association between psychiatric disorders and adherence to antidiabetes medications observed in the present study. Individuals with co-occurring diabetes and alcohol or drug abuse should be targeted for intensive interventions given their acute increased risk of mortality.

A comparison of the predictive abilities of dimensional and categorical models of unipolar depression in the National Comorbidity Survey

BACKGROUND

Taxometric research on depression has yielded mixed results, with some studies supporting dimensional solutions and others supporting taxonic solutions. Although supplementary tests of construct validity might clarify these mixed findings, to date such analyses have not been reported. The present study represents a follow-up to our previous taxometric study of depression designed to evaluate the relative predictive validities of dimensional and categorical models of depression.

METHOD

Two sets of dimensional and categorical models of depression were constructed from the depression items of the Composite International Diagnostic Interview: (1) empirically derived models obtained using latent structure analyses and (2) rationally selected models, including an additive depressive symptoms scale (dimensional) and DSM major depressive episodes (categorical). Both sets of dimensional and categorical models were compared in terms of their abilities to predict various clinically relevant outcomes (psychiatric diagnoses and impairment).

RESULTS

Factor analyses suggested a two-factor model ('cognitive-affective' and 'somatic' symptoms) and latent class analyses suggested a three-class model ('severe depression', 'moderate depression' and 'cognitive-affective distress'). In predictive analyses that simultaneously included dimensional and categorical models as predictors, the dimensional models remained significant unique predictors of outcomes while the categorical models did not.

CONCLUSIONS

Both dimensional models provided superior predictive validity relative to their categorical counterparts. These results provide construct validity evidence for the dimensional findings from our previous taxometric study and thus inspire confidence in dimensional conceptualizations of depression. It remains for future research to evaluate the construct validity of the taxonic solutions reported in the literature.

Initial Treatment Success Followed By Failure

This article presents a diagnostically complicated case involving comorbid major depressive disorder with psychotic features, social phobia and personality pathology (including avoidant, paranoid, and obsessive compulsive traits). “Mr. X” was a 45-year-old single White male who was unemployed and living with his parents at the time of treatment. He presented with severe anxiety (Beck Anxiety Inventory = 43) and depression (Beck Depression Inventory = 41) as well as active psychotic symptoms (e.g., self-depreciating auditory hallucinations). Although a cognitive case formulation and treatment plan led to initial success in terms of improvements in symptomatology and functional impairment, we speculate that failure to adequately address core toxic beliefs (e.g., “I am inadequate”) ultimately contributed to a precipitous return of symptomatology, followed by a suicide attempt and premature treatment termination. We discuss the challenges of working within a cognitive framework with this client and suggest alternative approaches that might have proven more successful.

A taxometric investigation of unipolar depression in the national comorbidity survey

Ongoing debate has questioned whether unipolar depression is a dimensional or categorical phenomenon. Although past studies using taxometric methods have supported a dimensional interpretation, each has suffered from methodological limitations. The present study was designed to overcome these limitations through reanalysis of the National Comorbidity Survey. Two indicator sets were constructed from the depression-relevant questions of the Composite International Diagnostic Interview. Participants who endorsed the lifetime occurrence of significant depressed mood or anhedonia (n=4,577) were submitted to 2 nonredundant taxometric procedures (maximum eigenvalue and means above minus below a cut), additional consistency tests, and recently developed simulation techniques. All results converged on a dimensional solution. The implications of these findings on assessment, treatment, and research design are discussed.