Nicotine metabolite ratio (3-hydroxycotinine/cotinine) in plasma and urine by different analytical methods and laboratories: implications for clinical implementation

BACKGROUND

The highly genetically variable enzyme CYP2A6 metabolizes nicotine to cotinine (COT) and COT to trans-3'-hydroxycotinine (3HC). The nicotine metabolite ratio (NMR, 3HC/COT) is commonly used as a biomarker of CYP2A6 enzymatic activity, rate of nicotine metabolism, and total nicotine clearance; NMR is associated with numerous smoking phenotypes, including smoking cessation. Our objective was to investigate the impact of different measurement methods, at different sites, on plasma and urinary NMR measures from ad libitum smokers.

METHODS

Plasma (n = 35) and urine (n = 35) samples were sent to eight different laboratories, which used similar and different methods of COT and 3HC measurements to derive the NMR. We used Bland-Altman analysis to assess agreement, and Pearson correlations to evaluate associations, between NMR measured by different methods.

RESULTS

Measures of plasma NMR were in strong agreement between methods according to Bland-Altman analysis (ratios, 0.82-1.16) and were highly correlated (all Pearson r > 0.96, P < 0.0001). Measures of urinary NMR were in relatively weaker agreement (ratios 0.62-1.71) and less strongly correlated (Pearson r values of 0.66-0.98, P < 0.0001) between different methods. Plasma and urinary COT and 3HC concentrations, while weaker than NMR, also showed good agreement in plasma, which was better than that in urine, as was observed for NMR.

CONCLUSIONS

Plasma is a very reliable biologic source for the determination of NMR, robust to differences in these analytical protocols or assessment site.

IMPACT

Together this indicates a reduced need for differential interpretation of plasma NMR results based on the approach used, allowing for direct comparison of different studies.

The Nicotine Metabolite Ratio is Associated With Early Smoking Abstinence Even After Controlling for Factors That Influence the Nicotine Metabolite Ratio

INTRODUCTION

The decrease in smoking rates in North America has plateaued, underscoring the need for new approaches to treat nicotine dependence. Inter-individual differences in smoking behavior result, in part, from variation in the rate of CYP2A6-mediated nicotine metabolism. A phenotypic measure of CYP2A6 activity is the nicotine metabolite ratio (NMR), the ratio of 3'hydroxycotinine/cotinine. The NMR is associated with smoking cessation. However, the NMR is also associated with genetic (eg, CYP2A6 genotype) and other (eg, sex and ethnicity) factors. Here we aimed to determine if previously identified non-CYP2A6 sources of variation in the NMR mitigated the association between the NMR and short-term abstinence.

METHODS

The NMR was determined from blood samples collected at intake from daily smokers aged 18-65. Biochemically-verified point prevalence abstinence (exhaled carbon monoxide level ≤ 8 ppm) was measured at 1 week following the target quit date in participants from a smoking cessation clinical trial (NCT01314001). Analyses were restricted to N = 462 blacks and N = 693 whites in the intent-to-treat sample.

RESULTS

Lower NMR (<0.31) was associated with a higher likelihood of 1-week abstinence (OR = 1.43; 95% CI = 1.12, 1.84). NMR was associated with abstinence even after controlling for treatment arm (nicotine patch or varenicline) and factors previously associated with NMR variation including sex, ethnicity, estrogen-containing hormonal therapy, body mass index, alcohol, and cigarette consumption.

CONCLUSIONS

NMR was associated with 1-week smoking abstinence; NMR may be a useful addition to medication screening approaches evaluating treatments for nicotine dependence.

Lack of Associations of CHRNA5-A3-B4 Genetic Variants with Smoking Cessation Treatment Outcomes in Caucasian Smokers despite Associations with Baseline Smoking

CHRNA5-A3-B4 variants, rs16969968, rs588765 and rs578776, are consistently associated with tobacco consumption among smokers, but the association with smoking cessation is less consistent. Among the studies that reported significant associations with cessation, the effects were observed in smokers treated with placebo treatment in some studies and conversely in those receiving active pharmacological therapy (bupropion and nicotine replacement therapies) in others. Thus, it remains unclear whether CHRNA5-A3-B4 is a useful marker for optimizing smoking cessation. Using data from 654 Caucasian smokers treated with placebo, nicotine patch or varenicline, we investigated whether CHRNA5-A3-B4 variants were associated with smoking cessation outcomes, and whether there were significant genotype-by-treatment or haplotype-by-treatment interactions. We observed no significant associations between CHRNA5-A3-B4 variants and smoking cessation, despite replicating previous associations with baseline tobacco consumption. At end of treatment the effect size on smoking cessation in the placebo, patch and varenicline groups for rs16969968 [GG vs. GA+AA] was OR = 0.66 (P = 0.23), OR = 1.01 (P = 0.99), and OR = 1.30 (P = 0.36) respectively, of rs588765 [CC vs. CT+TT] was OR = 0.96 (P = 0.90), OR = 0.84 (P = 0.58), and OR = 0.74 (P = 0.29) respectively, and for rs578776 [GG vs. GA+AA] on smoking cessation was OR = 1.02 (P = 0.95), OR = 0.75 (P = 0.35), and OR = 1.20 (P = 0.51) respectively. Furthermore, we observed no associations with cessation using the CHRNA5-A3-B4 haplotype (constructed using rs16969968 and rs588765), nor did we observe any significant genotype-by-treatment interactions, with or without adjusting for the rate of nicotine metabolism (all P>0.05). We also observed no significant genetic associations with 6 month or 12 month smoking abstinence. In conclusion, we found no association between CHRNA5-A3-B4 variants and smoking cessation rates in this clinical trial; however, as expected, significant associations with baseline tobacco consumption were replicated. Our data suggest that CHRNA5-A3-B4 gene variants do not exhibit a robust association with smoking cessation and are unlikely to be useful for clinically optimizing smoking cessation pharmacotherapy for Caucasian smokers.

Minimal evidence that untreated psychosis damages brain structures: a systematic review

INTRODUCTION

A longer duration of untreated psychosis (DUP) is associated with poor outcomes in first-episode psychosis (FEP); however, it is unclear whether this is due to the effects of psychosis on brain structure. We systematically reviewed the literature on the association between the length of untreated psychosis and brain structure in first-episode psychosis.

METHODS

We searched three electronic databases and conducted forward and backward citation searching to identify relevant papers. Studies were included if they: (1) included patients with a psychotic disorder who were treatment naïve or minimally treated; and (2) had correlated measures of DUP or duration of untreated illness (DUI) with structural measures.

RESULTS

We identified 48 studies that met the inclusion criteria. Forty-three examined the correlation between DUP and brain structure, and 19 examined the correlation between DUI and brain structure. There was evidence of significant associations in brain regions considered important in psychosis; however, the proportion of significant associations was low and the findings were inconsistent across studies. The majority of included studies were not primarily designed to examine whether DUP/DUI is correlated with brain structure, and there were methodological limitations in many studies that prevent drawing a strong conclusion.

CONCLUSION

To date, there is minimal evidence of an association between untreated psychosis and brain structure in FEP. Although the body of literature is substantial, there are few hypothesis-driven studies with a primary objective to answer this question. Future studies should be specifically designed to examine whether untreated psychosis has a deleterious effect on brain structure.

Use of the nicotine metabolite ratio as a genetically informed biomarker of response to nicotine patch or varenicline for smoking cessation: a randomised, double-blind placebo-controlled trial

BACKGROUND

Substantial variability exists in therapeutic response and adverse effects with pharmacotherapies for tobacco dependence. Biomarkers to optimise treatment choice for individual smokers might improve treatment outcomes. We tested whether a genetically informed biomarker of nicotine clearance, the nicotine metabolite ratio (NMR; 3'-hydroxycotinine:cotinine), predicts response to nicotine patch or varenicline for smoking cessation.

METHODS

We undertook NMR-stratified multicentre, randomised, placebo-controlled clinical trial from Nov 16, 2010, to Sept 12, 2014, at four sites. Smokers seeking treatment were randomly assigned by baseline NMR status and study site, in blocks of 12 patients (1:1:1 ratio), to 11 weeks of placebo (placebo pill plus placebo patch), nicotine patch (active patch plus placebo pill), or varenicline (active pill plus placebo patch), plus behavioural counselling. Participants and investigators were masked to group allocation and NMR status. An intention-to-treat analysis was done. Participants were followed up for 12 months after the target quit date. The primary endpoint was biochemically verified 7 day point prevalence abstinence at the end of treatment to estimate the pharmacological effect of treatment by NMR. The trial is registered at ClinicalTrials.gov, number NCT01314001.

FINDINGS

1246 participants (662 slow metabolisers of nicotine, 584 normal metabolisers of nicotine) were enrolled and randomly assigned to the three interventions (408 placebo, 418 nicotine patch, 420 varenicline). At end of treatment, varenicline was more efficacious than nicotine patch in normal metabolisers (OR 2·17, 95% CI 1·38-3·42; p=0·001), but not in slow metabolisers (OR 1·13, 0·74-1·71; p=0·56). In the longitudinal model including all timepoints, the NMR-by-treatment interaction was significant (ratio of odds ratios [ORR] 1·96, 95% CI 1·11-3·46; p=0·02). An NMR-by-treatment interaction showed that slow (vs normal) metabolisers reported greater overall side-effect severity with varenicline versus placebo (β=-1·06, 95% CI -2·08 to -0·03; p=0·044).

INTERPRETATION

Treating normal metabolisers with varenicline and slow metabolisers with nicotine patch could optimise quit rates while minimising side-effects.

FUNDING

National Institutes of Health, Canadian Institutes of Health Research, Abramson Cancer Center, Centre for Addiction and Mental Health Foundation, and Pennsylvania Department of Health.

A review of drug policy in the Golden Crescent: towards the development of more effective solutions

There is a high prevalence of drug trafficking and misuse in Asia. Drugs grown in Afghanistan are trafficked through Iran and Pakistan to the rest of the world. This has led to an increase in the prevalence of drug use disorders in these regions, especially heroin. This has in turn led to an increase in the use of syringes and syringe sharing which has resulted in the exponential spread of blood borne diseases such as HIV/AIDS. A lack of awareness of the detrimental use of heroin, syringe sharing and the concept of HIV has been revealed. The literature reviewed provides evidence for a change in policy with an increase in epidemiological and clinical research in these regions as well as an increase in public awareness.

The role of untreated psychosis in neurodegeneration: a review of hypothesized mechanisms of neurotoxicity in first-episode psychosis

For over 20 years, studies have tried to measure the association between the duration of untreated psychosis (DUP) and changes in brain morphology. A hypothesis that untreated psychosis is neurotoxic has been postulated, but the mechanisms of that toxicity have not been described. We re-analyzed papers collected for a systematic review to extract data on the hypotheses that have been generated on the potential mechanisms by which DUP could impact brain morphology in first-episode psychosis. Dopaminergic hyperactivity, prolonged hypothalamic-pituitary-adrenal activation, and persistent activity of catecholamines have been hypothesized as mechanisms to explain these associations. However, the question remains as to whether the observed structural changes are permanent or may be reversed via antipsychotic treatment.

Effects of tobacco smoking on neuropsychological function in schizophrenia in comparison to other psychiatric disorders and non-psychiatric controls

BACKGROUND AND OBJECTIVES

Compared to the general population cigarette smoking prevalence is elevated in psychiatric disorders such as schizophrenia (SZ), bipolar disorder (BD), and major depressive disorder (MDD). These disorders are also associated with neurocognitive impairments. Cigarette smoking is associated with improved cognition in SZ. The effects of smoking on cognition in BD and MDD are less well studied.

METHODS

We used a cross-sectional design to study neuropsychological performance in these disorders as a function of smoking status. Subjects (N = 108) were SZ smokers (n = 32), SZ non-smokers (n = 15), BD smokers (n = 10), BD non-smokers (n = 6), MDD smokers (n = 6), MDD non-smokers (n = 10), control smokers (n = 12), and control non-smokers (n = 17). Participants completed a neuropsychological battery; smokers were non-deprived.

RESULTS

SZ subjects performed significantly worse than controls in select domains, while BD and MDD subjects did not differ from controls. Three verbal memory outcomes were improved in SZ smokers compared with non-smokers; smoking status did not alter performance in BD or MDD.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

These data suggest that smoking is associated with neurocognitive improvements in SZ, but not BD or MDD. Our data may suggest specificity of cigarette-smoking modulation of neurocognitive deficits in SZ.

Cognitive remediation for individuals with psychosis in a supported education setting: a randomized controlled trial

Cognitive remediation (CR) has demonstrated good outcomes when paired with supported employment, however little is known about its effectiveness when integrated into a supported education program. This randomized controlled trial examined the effectiveness of integrating CR within a supported education program compared with supported education without CR. Thirty-seven students with psychosis were recruited into the study in the 2012 academic year. Academic functioning, cognition, self-esteem, and symptomatology were assessed at baseline, at 4months following the first academic term in which CR was provided, and at 8months assessing maintenance of gains. The treatment group demonstrated better retention in the academic program and a trend of improvement across a range of academic functional domains. While both treatment and control groups showed improvement in cognitive measures, the outcomes were not augmented by CR training. CR was also associated with significant and sustained improvements in self esteem. Further research, investigating specific intervention components is required to clarify the mixed findings regarding the effectiveness of CR in an education setting.

Known and novel sources of variability in the nicotine metabolite ratio in a large sample of treatment-seeking smokers

BACKGROUND

The ratio of 3'hydroxycotinine to cotinine, or nicotine metabolite ratio (NMR), is strongly associated with CYP2A6 genotype, CYP2A6-mediated nicotine and cotinine metabolism, and nicotine clearance. Higher NMR (faster nicotine clearance) is associated retrospectively with heavier smoking and lower cessation rates.

METHODS

NMR as a predictive biomarker of cessation outcomes is being investigated (NCT01314001). In addition to strong CYP2A6 genetic influences on NMR, demographic and hormonal factors alter NMR. Here, we analyzed, for the first time together, these sources of variation on NMR in smokers screened for this clinical trial (N = 1,672).

RESULTS

Participants (mean age = 45.9) were 65.1% Caucasian, 34.9% African American, and 54.8% male. Mean NMR (SD) was higher in Caucasians versus African Americans [0.41 (0.20) vs. 0.33 (0.21); P < 0.001], and in females versus males [0.41 (0.22) vs. 0.37 (0.20); P < 0.001]. Among females, birth control pill use (N = 17) and hormone replacement therapy (N = 14) were associated with 19.5% (P = 0.09) and 29.3% (P = 0.06) higher mean NMR, respectively, albeit nonsignificantly. BMI was negatively associated with NMR (Rho = -0.14; P < 0.001), whereas alcohol use (Rho = 0.11; P < 0.001) and cigarette consumption (Rho = 0.12; P < 0.001) were positively associated with NMR. NMR was 16% lower in mentholated cigarette users (P < 0.001). When analyzed together in a linear regression model, these predictors (each ≤2%) accounted for <8% of total NMR variation.

CONCLUSIONS

Although these factors significantly affected NMR, they contributed little (together <8%; each ≤2%) to total NMR variation.

IMPACT

Thus, when using NMR, for example, to prospectively guide smoking cessation therapy, these sources of variation are unlikely to cause NMR misclassification.

Varenicline for smoking cessation in bipolar disorder: a randomized, double-blind, placebo-controlled study

OBJECTIVE

Virtually no clinical trials for smoking cessation have been undertaken in bipolar disorder. Varenicline has shown efficacy for smoking cessation, but warnings about neuropsychiatric adverse events have been issued. We assessed the efficacy and safety of varenicline in euthymic bipolar subjects motivated to quit smoking.

METHOD

Clinically stable adult patients with DSM-IV bipolar disorder (n = 60) who smoked ≥ 10 cigarettes per day were randomized to a 3-month, double-blind, placebo-controlled varenicline trial and a 3-month follow-up. Study enrollment was completed from February 2010 through March 2013. Varenicline was dosed using standard titration, and smoking cessation counseling was provided to all patients. The primary outcome was defined as a 7-day point prevalence of self-reported no smoking verified by expired carbon monoxide level < 10 ppm at 12 weeks. Psychopathology and side-effects were assessed at each visit.

RESULTS

At 3 months (end of treatment), significantly more subjects quit smoking with varenicline (n/n = 15/31, 48.4%) than with placebo (n/n = 3/29, 10.3%) (OR = 8.1; 95% CI, 2.03-32.5; P < .002). At 6 months, 6 of 31 varenicline-treated subjects (19.4%) remained abstinent compared to 2 of 29 (6.90%) assigned to placebo (OR = 3.2; 95% CI, 0.60-17.6; P = .17). Psychopathology scores remained stable. Ten serious adverse events occurred (n = 6, varenicline; n = 4, placebo). Abnormal dreams occurred significantly more often in varenicline-treated subjects (n/n = 18/31, 61.3%) than in those receiving placebo (n/n = 9/29, 31%; Fisher exact test, P = .04). Eight varenicline-treated and 5 placebo-assigned subjects expressed fleeting suicidal ideation, a nonsignificant difference.

CONCLUSIONS

Varenicline shows efficacy for initiating smoking cessation in bipolar patients, but medication trials of longer duration are warranted for maintaining abstinence. Vigilance for neuropsychiatric adverse events is prudent when initiating varenicline for smoking cessation in this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01010204.

The relationship between the nicotine metabolite ratio and three self-report measures of nicotine dependence across sex and race

RATIONALE

Variability in the rate of nicotine metabolism, measured by the nicotine metabolite ratio (NMR), is associated with smoking behavior. However, data linking the NMR with nicotine dependence measured by the Fagerström test for nicotine dependence (FTND) are mixed. Few past studies have examined alternative measures of nicotine dependence and how this relationship may vary by sex and race.

OBJECTIVE

Using data from smokers undergoing eligibility evaluation for a smoking cessation clinical trial (n = 833), this study examined variability in the relationship between NMR and nicotine dependence across sex and race and using three measures of nicotine dependence: FTND, time-to-first-cigarette (TTFC), and the heaviness of smoking index (HSI).

RESULTS

Controlling for sex and race, nicotine metabolism was associated with nicotine dependence only when using the HSI (p < 0.05). Male normal metabolizers of nicotine were more likely to have high nicotine dependence based on the FTND and HSI (p < 0.05), but NMR was not related to measures of nicotine dependence in women. For African Americans, the NMR was associated with nicotine dependence only for the TTFC (p < 0.05), but NMR was not associated with nicotine dependence among Caucasians. Post hoc analyses indicated that the NMR was associated with cigarettes per day, overall, and among men and Caucasians (p < 0.05).

CONCLUSIONS

While there was some variation in the relationship between nicotine metabolism and nicotine dependence across measures and sex and race, the results indicate that this relationship may be more attributable to the association between NMR and cigarettes per day.

Stress-induced dopamine response in subjects at clinical high risk for schizophrenia with and without concurrent cannabis use

Research on the environmental risk factors for schizophrenia has focused on either psychosocial stress or drug exposure, with limited investigation of their interaction. A heightened dopaminergic stress response in patients with schizophrenia and individuals at clinical high risk (CHR) supports the dopaminergic sensitization hypothesis. Cannabis is believed to contribute to the development of schizophrenia, possibly through a cross-sensitization with stress. Twelve CHR and 12 cannabis-using CHR (CHR-CU, 11 dependent) subjects underwent [(11)C]-(+)-PHNO positron emission tomography scans, while performing a Sensorimotor Control Task (SMCT) and a stress condition (Montreal Imaging Stress task). The simplified reference tissue model was used to obtain binding potential relative to non-displaceable binding (BPND) in the whole striatum, its functional subdivisions (limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST)), globus pallidus (GP), and substantia nigra (SN). Changes in BPND, reflecting alterations in synaptic dopamine (DA) levels, were tested with analysis of variance. SMCT BPND was not significantly different between groups in any brain region (p>0.21). Although stress elicited a significant reduction in BPND in the CHR group, CHR-CU group exhibited an increase in BPND. Stress-induced changes in regional BPND between CHR-CU and CHR were significantly different in AST (p<0.001), LST (p=0.007), SMST (p=0.002), SN (p=0.021), and whole striatum (p=0.001), with trend level in the GP (p=0.099). All subjects experienced an increase in positive (attenuated) psychotic symptoms (p=0.001) following the stress task. Our results suggest altered DA stress reactivity in CHR subjects who concurrently use cannabis, as compared with CHR subjects. Our finding does not support the cross-sensitization hypothesis, which posits greater dopaminergic reactivity to stress in CHR cannabis users, but adds to the growing body of literature showing reduced DA (stress) response in addiction.

The association between cannabis use and depression: a systematic review and meta-analysis of longitudinal studies

BACKGROUND

Longitudinal studies reporting the association between cannabis use and developing depression provide mixed results. The objective of this study was to establish the extent to which different patterns of use of cannabis are associated with the development of depression using meta-analysis of longitudinal studies.

METHOD

Peer-reviewed publications reporting the risk of developing depression in cannabis users were located using searches of EMBASE, Medline, PsychINFO and ISI Web of Science. Only longitudinal studies that controlled for depression at baseline were included. Data on several study characteristics, including measures of cannabis use, measures of depression and control variables, were extracted. Odds ratios (ORs) were extracted by age and length of follow-up.

RESULTS

After screening for 4764 articles, 57 articles were selected for full-text review, of which 14 were included in the quantitative analysis (total number of subjects = 76058). The OR for cannabis users developing depression compared with controls was 1.17 [95% confidence interval (CI) 1.05-1.30]. The OR for heavy cannabis users developing depression was 1.62 (95% CI 1.21-2.16), compared with non-users or light users. Meta-regression revealed no significant differences in effect based on age of subjects and marginal difference in effect based on length of follow-up in the individual studies. There was large heterogeneity in the number and type of control variables in the different studies.

CONCLUSIONS

Cannabis use, and particularly heavy cannabis use, may be associated with an increased risk for developing depressive disorders. There is need for further longitudinal exploration of the association between cannabis use and developing depression, particularly taking into account cumulative exposure to cannabis and potentially significant confounding factors.

Randomized clinical trial of disulfiram for cocaine dependence or abuse during buprenorphine treatment

BACKGROUND

Disulfiram may be efficacious for treating cocaine dependence or abuse, possibly through inhibiting dopamine β-hydroxylase (DβH). Consequently, this randomized, placebo-controlled clinical trial of disulfiram during buprenorphine maintenance treatment evaluated the study hypothesis that disulfiram is superior to placebo and explored whether disulfiram response is greatest for participants with a single nucleotide polymorphism coding for genetically low DβH (T-allele carriers).

METHODS

We randomized 177 buprenorphine-treated opioid dependent participants with cocaine dependence or abuse to 12 weeks of double-blind treatment with disulfiram 250mg daily (n=91) or placebo (n=86). Of 155 participants genotyped, 84 were CC-homozygous, and 71 CT or TT genotypes. Primary outcomes included days per week cocaine use, number of cocaine-negative urine tests, and maximum consecutive weeks of cocaine abstinence. We analyzed an intention-to-treat comparison between disulfiram and placebo. We also explored potential pharmacogenetic interactions and examined treatment responses of four participant groups based on medication (disulfiram or placebo) by genotype (CC-homozygous or T-allele carrier) classification.

RESULTS

Disulfiram participants reported significantly less frequent cocaine use; the differences in cocaine-negative urine tests or consecutive weeks abstinence were not significant. Frequency of cocaine use was lowest in disulfiram-treated T-allele carriers; differences in cocaine-negative urine tests or consecutive weeks abstinence were not significant among the four medication-genotype groups.

CONCLUSIONS

The findings provide limited support for the efficacy of disulfiram for reducing cocaine use and suggest that its mechanism of action may involve inhibition of DβH. Further studies of its efficacy, mechanism of action, and pharmacogenetics of response are warranted.

Heightened D3 dopamine receptor levels in cocaine dependence and contributions to the addiction behavioral phenotype: a positron emission tomography study with [11C]-+-PHNO

The dopamine system is a primary treatment target for cocaine dependence (CD), but research on dopaminergic abnormalities (eg, D2 receptor system deficiencies) has so far failed to translate into effective treatment strategies. The D3 receptor system has recently attracted considerable clinical interest, and D3 antagonism is now under investigation as a novel avenue for addiction treatment. The objective here was to evaluate the status and behavioral relevance of the D3 receptor system in CD, using the positron emission tomography (PET) radiotracer [(11)C]-(+)-PHNO. Fifteen CD subjects (many actively using, but all abstinent 7-240 days on scan day) and fifteen matched healthy control (HC) subjects completed two PET scans: one with [(11)C]-(+)-PHNO to assess D3 receptor binding (BPND; calculated regionally using the simplified reference tissue model), and for comparison, a second scan with [(11)C]raclopride to assess D2/3 binding. CD subjects also completed a behavioral battery to characterize the addiction behavioral phenotype. CD subjects showed higher [(11)C]-(+)-PHNO BPND than HC in the substantia nigra, which correlated with behavioral impulsiveness and risky decision making. In contrast, [(11)C]raclopride BPND was lower across the striatum in CD, consistent with previous literature in 2 week abstinence. The data suggest that in contrast to a D2 deficiency, CD individuals may have heightened D3 receptor levels, which could contribute to addiction-relevant traits. D3 upregulation is emerging as a biomarker in preclinical models of addiction, and human PET studies of this receptor system can help guide novel pharmacological strategies for treatment.

Relationship between tobacco and cannabis use status in outpatients with schizophrenia

BACKGROUND AND OBJECTIVE

While high prevalence of tobacco and cannabis use are well established in schizophrenia, reports on their co-morbid use is limited. We explored the links between tobacco and cannabis use in an outpatient population meeting DSM-IV criteria for schizophrenia.

METHODS

Cigarette smoking behaviors were assessed in an outpaitent population with schizophrenia (N=54) with current (n=18), former (n=24), and no lifetime cannabis dependence (n=12).

RESULTS

We found significant differences in cigarettes per day (CPD) across groups: current dependent patients smoked less CPD than patients with former dependence and those with no history of dependence; former dependent patients smoked significantly less than patients with no history of cannabis dependence.

CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE

Preliminary results support an effect of cannabis use status on tobacco consumption. In the absence of cannabis, patients may increase cigarette smoking, suggesting state-dependent effects of cannabis on tobacco. Prospective designs should further examine this relationship between cannabis and tobacco in schizophrenia versus non-psychiatric controls.

Dopamine response to psychosocial stress in chronic cannabis users: a PET study with [11C]-+-PHNO

A number of addictions have been linked with decreased striatal dopamine (DA) receptor availability and DA release. Stress has a key role in cannabis craving, as well as in modulation of dopaminergic signaling. The present study aimed to assess DA release in response to a laboratory stress task with [(11)C]-(+)-PHNO positron emission tomography in cannabis users (CU). Thirteen healthy CU and 12 healthy volunteers (HV) were scanned during a sensorimotor control task (SMCT) and under a stress condition using the validated Montreal imaging stress task (MIST). The simplified reference tissue model (SRTM) was used to obtain binding potential (BP(ND)) in striatal subdivisions: limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST). Stress-induced DA release (indexed as a percentage of reduction in [(11)C]-(+)-PHNO BP (ND)) between CU and HV was tested with analysis of variance. SMCT BP(ND) was significantly higher in CU compared with HV in the AST (F=10.38, p=0.003), LST (F=4.95, p=0.036), SMST (F=4.33, p=0.048), and whole striatum (F=9.02, p=0.006). Percentage of displacement (change in BP(ND) between SMCT and MIST PET scans) was not significantly different across groups in any brain region, except in the GP (-5.03±14.6 in CU, compared with 6.15±12.1 in HV; F=4.39, p=0.049). Duration of cannabis use was significantly associated with stress-induced [(11)C]-(+)-PHNO displacement by endogenous DA in the LST (r=0.566, p=0.044), with no effect in any other brain region. In conclusion, despite an increase in striatal BP(ND) observed during the control task, chronic cannabis use is not associated with alterations in stress-induced DA release.

Treatment of tobacco dependence in people with mental health and addictive disorders

People with mental health and addictive disorders (MHADs) have higher rates of cigarette smoking, and less success in quitting smoking compared with the general population. Moreover, tobacco-related medical illness may be the leading cause of death in the MHAD population. We discuss the scope of this comorbidity, and approaches to the treatment of tobacco dependence in people with MHAD, including schizophrenia, mood disorders, anxiety disorders, and alcohol and substance use disorders. Finally, at the level of health systems, we emphasize the importance of integrated treatment of tobacco dependence in MHADs.