Neuropsychological assessment of adult patients with attention-deficit/hyperactivity disorder

Networks of Neuropsychological Functions in the Clinical Evaluation of Adult ADHD

This study applied network analysis to explore the relations between neuropsychological functions of individuals in the clinical evaluation of attention-deficit/hyperactivity disorder (ADHD) in adulthood. A total of 319 participants from an outpatient referral context, that is, 173 individuals with ADHD (ADHD group) and 146 individuals without ADHD (n-ADHD group), took part in this study and completed a comprehensive neuropsychological assessment. A denser network with stronger global connectivity was observed in the ADHD group compared to the n-ADHD group. The strongest connections were consistent in both networks, that is, the connections between selective attention and vigilance, and connections between processing speed, fluency, and flexibility. Further centrality estimation revealed attention-related variables to have the highest expected influence in both networks. The observed relationships between neuropsychological functions, and the high centrality of attention, may help identify neuropsychological profiles that are specific to ADHD and optimize neuropsychological assessment and treatment planning of individuals with cognitive impairment.

Neuropsychological functioning of individuals at clinical evaluation of adult ADHD

OBJECTIVES

Numerous studies showed that adults with attention deficit hyperactivity disorder (ADHD) suffer from impairments in a range of cognitive functions when compared to healthy controls. However, only little is known about the neuropsychological functions when compared to various clinical control groups and whether a distinct neuropsychological profile can be identified for adult ADHD.

METHOD

This retrospective study examined data of 199 outpatients referred for clinical evaluation of adult ADHD, allocated either to an ADHD group (n = 78) or to one of two clinical comparison groups, depending on whether they show indications (n = 71) or no indications (n = 50) for the presence of psychiatric disorders other than ADHD. All individuals performed a comprehensive neuropsychological test battery.

RESULTS

Data analysis revealed impairments in a range of cognitive functions in a substantial number of patients of all three groups. However, profiles of neuropsychological impairments were similar between groups. Furthermore, significant small- to medium-sized correlations between basic and higher-order cognitive functions were revealed in the ADHD group and the clinical comparison group with indications for psychiatric disorders other than ADHD.

CONCLUSION

Neuropsychological impairments are prominent in psychiatric outpatients seeking a clinical evaluation of adult ADHD but are not specific for ADHD. It is concluded that neuropsychological test performance may have limited incremental value to support the psychiatric differential diagnosis. Furthermore, a clinical trajectory may need to take into account that deficits in a range of higher-order cognitive functions can be substantially explained by deficits in basic cognitive functions.

Cognitive characterization of adult attention deficit hyperactivity disorder by domains: a systematic review

Attention deficit hyperactivity disorder (ADHD) is reportedly the most frequent neurodevelopmental disorder diagnosed during childhood, and it is recognized as a common condition in adulthood. We review the evidence to help identify cognitive domains associated to deficits in adult ADHD. A systematic review with narrative synthesis was performed, assessing studies on adult ADHD, neuropsychology and research on involved cognitive domains in adults 18+ years old with an established diagnosis of ADHD, in seven electronic databases (PubMed, PsychInfo, WebOfScience, Embase, Scopus, OvidSPMedline, and Teseo), and Worldcat and OpenGrey grey literature databases. 93 studies were included for this review, encompassing findings from a total 5574 adults diagnosed only with ADHD, medication-naïve or non-medicated at the moment of the assessment and 4880 healthy controls. Adults diagnosed with ADHD may show, when compared to healthy controls, a cognitive profile characterized by deficits across all attention modalities, processing speed, executive function (mainly working memory and inhibition with emphasis on reward delay and interference control), verbal memory, reading skills, social cognition and arithmetic abilities. A cognitive characterization of adult ADHD by domains is established beyond the sole consideration of attention and executive function problems. Along with these, verbal memory, language (mainly reading), social cognition and arithmetic abilities may also contribute to a more comprehensive characterization of the cognitive profile in adult ADHD.

A Preliminary Investigation of Deficits in Executive Functions of Adults With Attention Deficit Hyperactivity Disorder

Several studies over the past two decades have investigated the neuropsychological deficits in children with attention deficit hyperactivity disorder (ADHD), but much less has been done on adults. This study aimed to assess the deficits in executive functions of adults with ADHD, especially in the areas of attention, inhibition, impulsivity, and planning. Twenty-four adults (18 years and older) diagnosed with ADHD according to the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition criteria, and also assessed with Conners' Adult ADHD Rating Scale, participated in the study. Executive functions in cases were compared with 20 matched controls through the three instruments of Tower of London (TOL), Continuous Performance Test (CPT), and Stroop test. Performance of cases was weaker than that of the control group in TOL. The difference was significant in subsequent thinking time in most of the trials and number of movements only at level 2. In CPT, the adults with ADHD made more commission errors. In addition, the ADHD cases made more errors in the word card of the Stroop test, and the time they spent reading all three cards was significantly longer than that of the control group. Our study suggests that several deficits in executive functions related to ADHD persist into adulthood, such as impairments in planning time and set shifting, response inhibition, impulsivity, and visuolingual processing. However, simple (visual-motor processing) and sustained attention might improve with age.

Cognitive deficits and psychosocial functioning in adult ADHD: Bridging the gap between objective test measures and subjective reports

INTRODUCTION

Self-reported cognitive deficits in adult Attention-Deficit/Hyperactivity-Disorder (ADHD) are often not corroborated by standardized tests. Tests and reports also differ in their correspondence to aspects of psychosocial functioning. Executive function tasks (EF-tasks) using material close to daily life, may provide a more ecologically-valid assessment of cognitive deficits.

METHOD

36 adults with ADHD and 36 healthy controls performed standardized EF-tasks and corresponding EF-tasks using material close to daily life and gave self-reports on cognitive functioning. The study investigated performance differences and the predictive utility of cognitive measures for psychosocial functioning.

RESULTS

While all the self-reports showed substantial cognitive impairments for the ADHD group, this was only shown in some of task measures. For two domains, the deficits in EF-tasks with material close to daily life were similar or smaller than assessed with traditional measures. However, three tasks, which used material of daily life, revealed more deficits than the corresponding more standardized tasks. Beyond cognitive self-reports the new tasks did not contribute substantial to psychosocial functioning, similar to the standardized tasks.

CONCLUSIONS

Tasks using material close to daily life have the potential to objectify reported everyday life deficits better than more standardized tests, at least in single EF-domains. When relevant methodical aspects of these tasks will be more targeted and considered systematically in future research, the tasks might contribute to assessments of psychosocial functioning. Then they could also be used as outcome measures in intervention studies.

Do children with attention-deficit/hyperactivity disorder (ADHD) have set shifting deficits?

OBJECTIVE

Set shifting, or cognitive flexibility, is a core executive function involving the ability to quickly and efficiently shift back and forth between mental sets. Meta-analysis suggests medium-magnitude shifting impairments in attention-deficit/hyperactivity disorder (ADHD). However, this conclusion may be premature because the evidence-base relies exclusively on tasks that have been criticized for poor construct validity and may better reflect general neuropsychological functioning rather than shifting specifically.

METHOD

A well-characterized sample of 77 children ages 8-13 (M = 10.46, SD = 1.54; 32 girls; 66% Caucasian/non-Hispanic) with ADHD (n = 43) and without ADHD (n = 34) completed the criterion global-local set shifting task and 2 counterbalanced control tasks that were identical in all aspects except the key processes.

RESULTS

The experimental manipulation was successful at evoking set shifting demands during the global-local versus both nonshift control tasks (p < .001; ω2 = .12-.14). Mixed-model analyses of variance (ANOVAs) revealed that the ADHD group did not demonstrate disproportional decrements in speed shift costs on the shifting versus nonshift control tasks (p = .30; ω2 = .002), suggesting no evidence of impaired set shifting abilities in ADHD. In contrast, the ADHD group made disproportionately more shifting errors than the non-ADHD group (p = .03; ω2 = 0.03) that were more parsimoniously attributable to prerequisite (nonshifting) processes necessary for successful performance on the global-local task.

CONCLUSIONS

Children with ADHD's impaired performance on shifting tasks may be attributable to difficulties maintaining competing rule sets and/or inhibiting currently active rule sets prior to shifting. However, when these higher-order processes are executed successfully, there is no significant evidence to suggest a unique set shifting deficit in ADHD. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

High serum high-density lipoprotein-cholesterol is associated with memory function and gyrification of insular and frontal opercular cortex in an elderly memory-clinic population

The issue of whether serum lipid marker values are cognitively and neurologically significant for elderly individuals attending a memory clinic has been controversial. We investigated the associations of serum lipid markers with the memory function and cortical structure in 52 patients aged ≥75 years who had attended our memory clinic based on their subjective memory complaints. None had a history of medication for hyperlipidemia. The Wechsler Memory Scale-Revised (WMS-R) was administered to all patients for the assessment of their memory function. Serum low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDLC), and triglyceride (TG) were measured for each patient. Surface-based morphometry (SBM) was performed for the calculation of each patient's cortical thickness and gyrification index based on structural MRI data. Our analyses revealed that the serum HDLC level was positively and significantly correlated with the WMS-R subtests of visual paired associates I/II and logical memory I (p < 0.05). The serum TG level was negatively correlated with the logical memory I subtest. The SBM results showed positive correlations between the serum HDLC level and the gyrification indices of the bilateral insular and frontal opercular cortices, and those two gyrification indices were positively correlated with the logical memory I and visual paired associates I/II. These results suggest that in these elderly patients, a high serum HDLC level was associated with not only preserved memory function but also gyrification of the insular and frontal opercular cortex. We conclude that elderly individuals' serum lipid markers should be carefully assessed in memory clinic settings, because serum HDLC may be a biomarker for memory function and cortical structure.

Comparison of the Computer and Hand Administered Versions of the Brown Location Test (BLT)

Objective

The Brown Location Test (BLT) was developed to remedy some of the problems in existing visual-based memory tests. The hand version has demonstrated good psychometric properties, the ability to provide lateralization information for mesial temporal lobe epilepsy patients, and has normative data. The purpose of this study was to compare the hand administered format to the more recently developed computer administered format.

Methods

We used Generalizability Theory analyses to assess the degree of variability in scores across the hand and computer versions of the test, and across alternate test forms, A and B. We also compared the means and standard deviations for the different versions and forms using paired t-tests, and Pearson correlation coefficients.

Results

There was minimal variability and high levels of score similarity across the various test administration formats and forms.

Conclusions

The high degree of comparability between versions allows one to apply the validity findings and normative data collected using the hand administered version to the computer version of the BLT.

Differential Effects of the Factor Structure of the Wechsler Memory Scale-Revised on the Cortical Thickness and Complexity of Patients Aged Over 75 Years in a Memory Clinic Setting

The Wechsler Memory Scale-Revised (WMS-R) is one of the internationally well-known batteries for memory assessment in a general memory clinic setting. Several factor structures of the WMS-R for patients aged under 74 have been proposed. However, little is known about the factor structure of the WMS-R for patients aged over 75 years and its neurological significance. Thus, we conducted exploratory factor analysis to determine the factor structure of the WMS-R for patients aged over 75 years in a memory clinic setting. Regional cerebral blood flow (rCBF) was calculated from single-photon emission computed tomography data. Cortical thickness and cortical fractal dimension, as the marker of cortical complexity, were calculated from high resolution magnetic resonance imaging data. We found that the four factors appeared to be the most appropriate solution to the model, including recognition memory, paired associate memory, visual-and-working memory, and attention as factors. Patients with mild cognitive impairments showed significantly higher factor scores for paired associate memory, visual-and-working memory, and attention than patients with Alzheimer's disease. Regarding the neuroimaging data, the factor scores for paired associate memory positively correlated with rCBF in the left pericallosal and hippocampal regions. Moreover, the factor score for paired associate memory showed most robust correlations with the cortical thickness in the limbic system, whereas the factor score for attention correlated with the cortical thickness in the bilateral precuneus. Furthermore, each factor score correlated with the cortical fractal dimension in the bilateral frontotemporal regions. Interestingly, the factor scores for the visual-and-working memory and attention selectively correlated with the cortical fractal dimension in the right posterior cingulate cortex and right precuneus cortex, respectively. These findings demonstrate that recognition memory, paired associate memory, visual-and-working memory, and attention can be crucial factors for interpreting the WMS-R results of elderly patients aged over 75 years in a memory clinic setting. Considering these findings, the results of WMS-R in elderly patients aged over 75 years in a memory clinic setting should be cautiously interpreted.

Long-Term Memory Performance in Adult ADHD

OBJECTIVE

Memory problems are a frequently reported symptom in adult ADHD, and it is well-documented that adults with ADHD perform poorly on long-term memory tests. However, the cause of this effect is still controversial. The present meta-analysis examined underlying mechanisms that may lead to long-term memory impairments in adult ADHD.

METHOD

We performed separate meta-analyses of measures of memory acquisition and long-term memory using both verbal and visual memory tests. In addition, the influence of potential moderator variables was examined.

RESULTS

Adults with ADHD performed significantly worse than controls on verbal but not on visual long-term memory and memory acquisition subtests. The long-term memory deficit was strongly statistically related to the memory acquisition deficit. In contrast, no retrieval problems were observable.

CONCLUSION

Our results suggest that memory deficits in adult ADHD reflect a learning deficit induced at the stage of encoding. Implications for clinical and research settings are presented.

Attenuated Readiness Potential in the Absence of Executive Dysfunction in Adults With ADHD

OBJECTIVE

Patients with ADHD display a decreased contingent negative variation in Go/NoGo tasks. It is unclear whether the attenuation is due to deficits of executive function or to disorder of motor planning. The readiness potential (RP) recorded during self-initiated movements could cast light on this question.

METHOD

RP was recorded in 25 stably medicated adult ADHD patients and 21 healthy controls matched for age, education, and verbal IQ. Participants also completed neuropsychological tests of executive function.

RESULTS

Compared with healthy controls, ADHD patients showed significantly diminished RP peaks and also decreased negativity in preparation of the movement at frontal locations. There were no significant group differences with regard to tests of executive function.

CONCLUSION

In adults with ADHD, deficits of motor organization are also manifest in situations not involving external stimulus processing. The attenuated RP occurred in the absence of executive dysfunction. Results are consistent with partial independence between motor and executive dysfunction in ADHD.

Allocentric but not egocentric visual memory difficulties in adults with ADHD may represent cognitive inefficiency

Attention Deficit Hyperactivity Disorder (ADHD) has often been conceptualized as arising executive dysfunctions (e.g., inattention, defective inhibition). However, recent studies suggested that cognitive inefficiency may underlie many ADHD symptoms, according to reaction time and processing speed abnormalities. This study explored whether a non-timed measure of cognitive inefficiency would also be abnormal. A sample of 23 ADHD subjects was compared to 23 controls on a test that included both egocentric and allocentric visual memory subtests. A factor analysis was used to determine which cognitive variables contributed to allocentric visual memory. The ADHD sample performed significantly lower on the allocentric but not egocentric conditions. Allocentric visual memory was not associated with timed, working memory, visual perception, or mental rotation variables. This paper concluded by discussing how these results supported a cognitive inefficiency explanation for some ADHD symptoms, and discussed future research directions.

Comorbid attention-deficit/hyperactivity disorder in adult psychiatric outpatients with depressive or anxiety disorders

BACKGROUND

There are very few studies reporting on the prevalence and the contribution of not previously diagnosed ADHD in the clinical picture of other psychiatric disorders. The aim of our study is to determine the prevalence and clinical correlates of comorbid attention deficit/hyperactivity disorder (ADHD) in adult psychiatric outpatients with depressive or anxiety disorders.

METHODS

During a 6-month period, 114 outpatients with depressive or anxiety disorders were evaluated for ADHD diagnosis. Assessment included interviews with both patient and relatives/friends and the use of a daily diary. Moreover, the patients completed the self-report scales Beck Depression Inventory (BDI), Spielberger's Anxiety Inventory (STAI), and the Symptom Checklist-90-R Rating Scale (SCL-90-R).

RESULTS

A total of 22 out of 114 patients (19.3%) received an ADHD diagnosis for the first time in their life. Comorbid ADHD compared to non ADHD patients scored significantly higher (p < 0.05) for depression (BDI), state and trait anxiety (STAI) and in the following SCL-90-R factors: Positive Symptoms Distressing Index, Positive Symptoms Index, Somatization, Obsessive Compulsive, Depression, Anxiety, and Hostility.

CONCLUSIONS

ADHD might go unrecognized among psychiatric outpatients. Patients with depressive or anxiety disorder reporting more severe symptomatology should be carefully screened for possible comorbid adult ADHD.

Dysfunctional cortical inhibition in adult ADHD: neural correlates in auditory event-related potentials

In recent times, the relevance of an accurate diagnosis of attention-deficit/hyperactivity disorder (ADHD) in adults has been the focus of several studies. No longer considered a pathology exclusive to children and adolescents, and taking into account its social implications, developing enhanced support tools for the current diagnostic procedure becomes a priority. Here we present a method for the objective assessment of ADHD in adults using chirp-evoked, paired auditory late responses (ALRs) combined with a two-dimensional ALR denoising scheme to extract correlates of intracortical inhibition. Our method allows for an effective single-sweep denoising, thus requiring less trials to obtain recognizable physiological features, useful as pointers of cortical impairment. Results allow an optimized diagnosis, reduction of data loss and acquisition time; moreover, they do not account exclusively for critical elements within clinical evaluations, but also allow studying the pathophysiology of the condition by providing objective information regarding impaired cortical functions.

ADHD Preschoolers with and without ODD: do they act differently depending on degree of task engagement/reward?

OBJECTIVE

To examine the impact of reinforcement on reaction time (RT) and RT variability (RT standard deviation [RTSD]) in preschoolers with ADHD with and without oppositional defiant disorder (ODD), and a typically developing (TD) comparison group.

METHOD

Participants were administered a computerized task consisting of two conditions: simple RT (SRT) and reinforced SRT (SRTr). Data were analyzed using two-way (Group × Condition) mixed ANOVAs and followed-up using pairwise comparisons.

RESULTS

RTs were significantly shorter and less variable during the SRTr than the SRT condition. A significant Group x Condition interaction was observed for RTSD (F= 3.38, p < .05); post hoc analyses indicated that the RTSD of the ADHD + ODD group was significantly more variable than that of the TD group during the SRT condition (F = 4.81, p < .05). However, their RTSD was statistically indistinguishable from the other groups during the SRTr condition.

CONCLUSION

Preschoolers who are oppositional/defiant and hyperactive are the most responsive to feedback/reward.

Brain activation deficit in increased-load working memory tasks among adults with ADHD using fMRI

Working memory (WM) is impaired among adults with attention-deficit hyperactivity disorder (ADHD). This study aimed to investigate the brain activation deficit for low-level or increased-load WM among adults with ADHD. A total of 20 adults with ADHD and controls were recruited according to diagnostic interviewing by a psychiatrist. Phonological and visual-spatial 2-back and 3-back tasks were performed under functional magnetic resonance scanning. The results demonstrated that both the adults with ADHD and the controls exhibited activation of the fronto-parietal network for WM, and the intensity was greater in the adult ADHD group. The ADHD group had higher brain activation over the bilateral anterior cingulate, left inferior frontal lobe, hippocampus, and supplementary motor area (SMA) for phonological WM than the control group. When the task loading increased from 2-back to 3-back tasks, the adults with ADHD perceived greater difficulty. The control group exhibited increased brain activation over the frontal-parietal network in response to increased phonological WM load. However, the ADHD group showed decreased brain activation over the left precuneus, insula, and SMA. Further analysis demonstrated that the ADHD group exhibited a greater decrease in brain activation over the left fronto-parietal network, including the precuneus, SMA, insula/inferior frontal lobe, and dorsolateral prefrontal cortex, than the control group. These results suggest that adults with ADHD pay more effort to low demanding phonological WM. On the other hand, brain activation of the left fronto-parietal network is impaired when the demands of WM exceed the capacity of adults with ADHD.

A head-to-head randomized clinical trial of methylphenidate and atomoxetine treatment for executive function in adults with attention-deficit hyperactivity disorder

Results regarding the effects of methylphenidate and atomoxetine on executive functions were inconsistent and no study has directly compared the efficacy of these two medications in improving executive functions in adults with attention-deficit hyperactivity disorder (ADHD). We conducted an 8-10 wk, open-label, head-to-head, randomized clinical trial involving adults with a clinical diagnosis of ADHD confirmed by psychiatric interview. The two treatment arms were immediate-release methylphenidate (IR-methylphenidate) (n = 31) and atomoxetine once daily (n = 32). Executive functions were assessed by the Cambridge Neuropsychological Test Automated Battery (CANTAB), including spatial working memory, spatial span, intra-extra dimensional set shifts, rapid visual information processing and Stockings of Cambridge (SOC). In addition to the symptom assessments at baseline (week 0), visit 2 (week 4-5) and visit 3 (week 8–10), they received CANTAB assessments at baseline and visit 3 (60.4 ± 6.3 d). Compared to baseline, adults treated with atomoxetine showed significant improvement in spatial working memory, spatial short-term memory, sustained attention and spatial planning at visit 3; adults treated with IR-methylphenidate showed significant improvement in spatial working memory at visit 3. Comparing the magnitude of improvement in executive functions between these two medications, the effect was generally similar for the two groups, although atomoxetine might have significantly greater efficacy than IR-methylphenidate in terms of improving spatial planning (SOC). Our results provide evidence to support that both IR-methylphenidate and atomoxetine improved various executive functions in adults with ADHD with greater improvement in atomoxetine than IR-methylphenidate in spatial planning.

The genetics of attention deficit/hyperactivity disorder in adults, a review

The adult form of attention deficit/hyperactivity disorder (aADHD) has a prevalence of up to 5% and is the most severe long-term outcome of this common neurodevelopmental disorder. Family studies in clinical samples suggest an increased familial liability for aADHD compared with childhood ADHD (cADHD), whereas twin studies based on self-rated symptoms in adult population samples show moderate heritability estimates of 30-40%. However, using multiple sources of information, the heritability of clinically diagnosed aADHD and cADHD is very similar. Results of candidate gene as well as genome-wide molecular genetic studies in aADHD samples implicate some of the same genes involved in ADHD in children, although in some cases different alleles and different genes may be responsible for adult versus childhood ADHD. Linkage studies have been successful in identifying loci for aADHD and led to the identification of LPHN3 and CDH13 as novel genes associated with ADHD across the lifespan. In addition, studies of rare genetic variants have identified probable causative mutations for aADHD. Use of endophenotypes based on neuropsychology and neuroimaging, as well as next-generation genome analysis and improved statistical and bioinformatic analysis methods hold the promise of identifying additional genetic variants involved in disease etiology. Large, international collaborations have paved the way for well-powered studies. Progress in identifying aADHD risk genes may provide us with tools for the prediction of disease progression in the clinic and better treatment, and ultimately may help to prevent persistence of ADHD into adulthood.

Assessment of post-excitatory long-interval cortical inhibition in adult attention-deficit/hyperactivity disorder

In order to further examine cortical impairment in adult ADHD patients and to test the hypothesis of a disturbed neuronal inhibition in adults with ADHD, late auditory evoked potentials were measured. By using paired-chirp auditory late responses, we compared 15 adults with ADHD with 15 control subjects, focusing on the inhibition elicited by the stimuli. Besides amplitude measurements, a time-frequency phase coherence study using the wavelet phase synchronization stability (WPSS) was performed. ADHD was diagnosed according to DSM-IV criteria. All ADHD subjects were without medication and did not suffer from any further axis I disorder. WPSS analysis revealed impaired auditory inhibition for ADHD patients for interstimulus intervals (ISI) between 500 and 1,100 ms as compared with healthy controls. By analyzing the WPSS in the interval from 80 ms to 220 ms, mean inhibition of the test chirp was found to be 6% in the ADHD group and 38.5% in the control subjects (p = 0.01). Moreover, overall smaller amplitudes in the N100 and P200 waves at all ISI were found (p = 0.04 and p = 0.02). However, reproducibility indices in the amplitude measurements were low, thus supporting the use of the instantaneous phase-based analysis method. The results support the hypothesis of reduced intracortical inhibition as a correlate of disturbed brain function in adults with ADHD.

Visual memory as a potential cognitive endophenotype of attention deficit hyperactivity disorder

BACKGROUND

Executive functions have been proposed as endophenotypes for attention deficit hyperactivity disorder (ADHD); however, data regarding visual memory are lacking. We therefore assessed visual memory in adolescents with ADHD and their unaffected siblings compared with controls.

METHOD

The participants included 279 adolescents with ADHD, 108 unaffected siblings, and 173 unaffected school controls. They were assessed by using the visual memory tasks of the Cambridge Neuropsychological Test Automated Battery (CANTAB): Delayed Matching to Sample (DMS), Spatial Recognition Memory (SRM), Paired Associates Learning (PAL), and Pattern Recognition Memory (PRM).

RESULTS

Compared with the controls, probands with ADHD had a significantly lower number of correct responses, a higher probability of an error following a correct response and following an error response in the DMS, and a lower percentage of correct responses in the SRM. Their unaffected siblings occupied an intermediate position between ADHD probands and controls in the probability of an error following a correct response and following an error response in the DMS, and in the percentage of correct responses in the SRM. In general, lower IQ and current use of and duration of treatment with methylphenidate were associated with more severe visual memory deficits.

CONCLUSIONS

The present results suggest that ADHD is associated with poorer visual memory function. Visual memory assessed by the DMS and SRM tasks in the CANTAB may be a useful endophenotype for ADHD.

Set shifting in a rodent model of attention-deficit/hyperactivity disorder

Two experiments compared spontaneously hypertensive rats (SHRs; a rodent model of attention-deficit/hyperactivity disorder) and Wistar rats (a normoactive control strain), on the acquisition of a set-shifting strategy. In Experiment 1, SHRs and Wistar rats were equivalent in trials to criterion to learn a brightness or a texture discrimination but SHRs were faster than Wistar rats in shifting to the opposite discrimination when there was 1 or 2 days between the initial discrimination and the shift. In Experiment 2, SHRs and Wistar rats were equivalent in shifting when the shift between discriminations occurred immediately after a criterion had been met in the first discrimination. The results are discussed in terms of a failure of SHRs to store or retrieve an initial discrimination and/or latent inhibition over a delay, leading to faster acquisition of a set-shift. This failure in storage or retrieval may be the result of a hypoactive dopamine system in the prefrontal cortex and nucleus accumbens shell as well as abnormalities in entorhinal cortex in SHRs.

Response inhibition and reward anticipation in medication-naïve adults with attention-deficit/hyperactivity disorder: a within-subject case-control neuroimaging study

BACKGROUND

Previous research suggests that ADHD patients are characterized by both reduced activity in the inferior frontal gyrus (IFG) during response inhibition tasks (such as the Go-NoGo task), and reduced activity in the ventral striatum during reward anticipation tasks (such as the Monetary-Incentive-Delay [MID] task). However, no prior research has applied either of these paradigms in medication-naïve adults with ADHD, nor have these been implemented in an intrasubject manner.

METHODS

The sample consisted of 19 medication-naïve adults with ADHD and 19 control subjects. Main group analyses were based on individually defined regions of interest: the IFG and the VStr for the Go-NoGo and the MID task respectively. In addition, we analyzed the correlation between the two measures, as well as between these measures and the clinical symptoms of ADHD.

RESULTS

We observed reduced bilateral VStr activity in adults with ADHD during reward anticipation. No differences were detected in IFG activation on the Go-NoGo paradigm. Correlation analyses suggest that the two tasks are independent at a neural level, but are related behaviorally in terms of the variability of the performance reaction time. Activity in the bilateral VStr but not in the IFG was associated negatively with symptoms of hyperactivity/impulsivity.

CONCLUSIONS

Results underline the implication of the reward system in ADHD adult pathophysiology and suggest that frontal abnormalities during response inhibition performance may not be such a pivotal aspect of the phenotype in adulthood. In addition, our findings point toward response variability as a core feature of the disorder.

Set shifting and working memory in adults with attention-deficit/hyperactivity disorder

Compared to the high number of studies that investigated executive functions (EF) in children with attention-deficit/hyperactivity disorder (ADHD), a little is known about the EF performance of adults with ADHD. This study compared 37 adults with ADHD (ADHD(total)) and 32 control participants who were equivalent in age, intelligence quotient (IQ), sex, and years of education, in two domains of EF--set shifting and working memory. Additionally, the ADHD(total) group was subdivided into two subgroups: ADHD patients without comorbidity (ADHD(-), n = 19) and patients with at least one comorbid disorder (ADHD(+), n = 18). Participants fulfilled two measures for set shifting (i.e., the trail making test, TMT and a computerized card sorting test, CKV) and one measure for working memory (i.e., digit span test, DS). Compared to the control group the ADHD(total) group displayed deficits in set shifting and working memory. The differences between the groups were of medium-to-large effect size (TMT: d = 0.48; DS: d = 0.51; CKV: d = 0.74). The subgroup comparison of the ADHD(+) group and the ADHD(-) group revealed a poorer performance in general information processing speed for the ADHD(+) group. With regard to set shifting and working memory, no significant differences could be found between the two subgroups. These results suggest that the deficits of the ADHD(total) group are attributable to ADHD rather than to comorbidity. An influence of comorbidity, however, could not be completely ruled out as there was a trend of a poorer performance in the ADHD(+) group on some of the outcome measures.

Independent contributions of cognitive functioning and social risk factors to symptoms of ADHD in two nordic populations-based cohorts

This study examined independent contributions of executive functioning (EF), state regulation (SR), and social risk factors to symptom dimensions of attention deficit hyperactivity disorder (ADHD) in two cohorts, which included 221 Norwegian children and 294 Finnish adolescents. Independent contributions of EF and SR were shown in the Norwegian cohort and EF contributed independently in the Finnish cohort. When controlling for each symptom dimension, cognitive functioning and social risk factors were differentially associated with inattention and hyperactivity/impulsivity symptoms. The results show the need to include both social risk factors and cognitive functioning to obtain a better understanding of ADHD symptoms.

How do different diagnostic criteria, age and gender affect the prevalence of attention deficit hyperactivity disorder in adults? An epidemiological study in a Hungarian community sample

The goal of the study was twofold: (1) to investigate the effect of different diagnostic criteria on prevalence estimates of adult attention deficit hyperactivity disorder (ADHD), and (2) to provide prevalence estimates of adult ADHD for the first time in a Hungarian sample. Subjects between 18 and 60 years were included in the screening phase of the study (N = 3,529), conducted in 17 GP practices in Budapest. Adult self-report scale 6-item version was used for screening. Out of 279 positively screened subjects 161 subjects participated in a clinical interview and filled out a self-report questionnaire to confirm the diagnosis. Beside DSM-IV diagnostic criteria, we applied four alternative diagnostic criteria: 'No-onset' (DSM-IV criteria without the specific requirement for onset); full/Sx (DSM-IV "symptoms only" criteria); and reduced/Sx (DSM-IV "symptoms only" criteria with a reduced threshold for symptom count). Crude prevalence estimates adjusted for the specificity and sensitivity data of the screener were 1.35% in the 'DSM-IV' group, 1.64% in the 'No-onset' group, 3.65% in the 'Sx/full' group and 4.16% in the 'Sx/reduced' group. Logistic regression analysis showed that ADHD was significantly more prevalent with younger age and male gender [chi(2) = 14.46; P = 0.0007]. Prevalence estimates corrected for the 'not-interviewed' subsample and adjusted for specificity and sensitivity data of the screener was 2.3% in males, 0.91% in females; 2.02% in the < or =40 years age group and 0.70% in the >40 years age group, based on DSM-IV diagnostic criteria. Prevalence rates found in this study are somewhat lower, but still are in line with those reported in the literature.

What are the cognitive effects of stimulant medications? Emphasis on adults with attention-deficit/hyperactivity disorder (ADHD)

The relevant literature concerning cognitive effects of amphetamine and methylphenidate, was reviewed, with an emphasis on research conducted in adults diagnosed with attention-deficit/hyperactivity disorder. As first-line treatment for ADHD, stimulant drugs are well-known to improve attention and concentration. Yet, there is increasing evidence that (as with children and adolescents), they do not promote learning and academic achievement in adult college students with ADHD. A review of neuropsychological studies indicates that, although response latencies are reduced, performance of ADHD adults on tests of 'distractibility' and 'planning' is also not consistently improved by stimulants. Studies in non-ADHD adults suggest that stimulants do not promote acquisition of new information, might improve retention of previously acquired information, and facilitate memory consolidation, but may actually impair performance of tasks that require adaptation, flexibility and planning. It is still not clear if improvement only occurs when there is a baseline deficit. Stimulants may influence cognition by their effects on physiological arousal. Regardless, the evidence does not support the conclusion that stimulants are cognitive 'enhancers.'

[Neuro-enhancement from an addiction specialist's viewpoint]

The use of medications to enhance performance in healthy individuals is increasingly being propagated even by neuroscientists under such colorful terms as"neuro-enhancement". A large number of medications, including psychostimulants have been advocated in this context. Recent data from the German health insurance company DAK indicate that a number of employees already take medications to fulfill their professional needs and enhance performance. The use of new drugs in the healthy has even been advocated by prominent neurobiologists in a commentary in a recent edition of Nature. There are a number of ethical objections to this use and there is an apparent risk of addiction. To date German psychiatrists have surprisingly not been outspoken on this issue. The author would like to make an emphatic plea against"brain doping" in healthy individuals.

Unwanted intrusive and worrisome thoughts in adults with Attention Deficit\Hyperactivity Disorder

Attention Deficit/Hyperactivity Disorder (ADHD) is associated with deficient motor and cognitive inhibitory mechanisms. The aim of this article is to examine two symptoms associated with cognitive disinhibition, namely: intrusive unwanted thoughts, worrisome thoughts and their suppression. Thirty-seven college students diagnosed with ADHD and 23 healthy college students were compared on the Distressing Thoughts Questionnaire and on the Anxious Thoughts Inventory. Results show that in comparison to the control group, participants with ADHD experienced significantly higher ratings on all intrusive thoughts scales, and three worrisome thoughts scales. Our results suggest that worrisome intrusive thoughts are an important phenotypical expression of adults with ADHD. A neurobiological explanation for this phenomenon is suggested, and clinical implications are discussed.

Attention deficit hyperactivity disorder (ADHD): gender- and age-related differences in neurocognition

BACKGROUND

Despite the growing recognition that the clinical symptom characteristics associated with attention deficit hyperactivity disorder (ADHD) persist into adulthood in a high proportion of subjects, little is known about the persistence of neurocognitive deficits in ADHD. The objective was twofold: (1) to conduct a meta-analysis of neuropsychological studies to characterize attentional performance in subjects with adult ADHD by examining differences in ADHD versus normal control subjects; and (2) to investigate whether these differences vary as a function of age and gender.

METHOD

Twenty-five neuropsychological studies comparing subjects with adult ADHD and healthy controls were evaluated. Statistical effect size was determined to characterize the difference between ADHD and control subjects. Meta-regression analysis was applied to investigate whether the difference between ADHD and control subjects varied as a function of age and gender across studies.

RESULTS

Tests measuring focused and sustained attention yielded an effect size with medium to large magnitude whereas tests of simple attention resulted in a small to medium effect size in terms of poorer attention functioning of ADHD subjects versus controls. On some of the measures (e.g. Stroop interference), a lower level of attention functioning in the ADHD group versus the controls was associated with male gender.

CONCLUSIONS

Adult ADHD subjects display significantly poorer functioning versus healthy controls on complex but not on simple tasks of attention, and the degree of impairment varies with gender, with males displaying a higher level of impairment.