Dimensional Measures Research Articles

Homo- and Heterotypic Trajectories in a Preschool to Primary-School Clinical Sample: A Prospective Study Related to Maternal Psychopathology.

Background: Most longitudinal or follow-up mental health studies describe developmental pathways using dimensional measures of psychopathology, but seldom using pathways described by clinical disorders.Objective: We aim to describe diagnostic pathways by homotypic (within the disorder continuity) and heterotypic development (between the disorder continuity), with maternal psychopathology as moderator for both trajectories.Methods: Clinically referred children (0–7 years; N = 83) were assessed at preschool age and at primary-school age through a clinical interview. We built a disorder cluster of emotional disorders (ED; F32, F40, F42, F43, F93.0, F93.1, F93.2, F93.8, F95), behavioral disorders (BD; F68.8, F90, F91, F91.3, F93.3, F93.9, F94), and specific early onset disorders (SEO; F50, F51, F70, F98.0, F98.1, F98.2, F98.8, F98.9). We describe the prevalence, comorbidity, and clinical trajectories of various types of homotypic and heterotypic development.Results: We observed a high rate of comorbidity throughout the study (62.6% at admission and 67.5% at follow-up) and in general, a high continuity of mental health problems from preschool to primary-school age children (69.9% of the sample showed continuity), with 50.6% of the sample showing homotypic and 44.6% showing heterotypic development. Hierarchical multiple regression analyses suggest that heterotypic development may be influenced by maternal psychopathology.Conclusion: Currently, evidence-based mental health guidelines for preschool populations are designed and evaluated assuming a homotypic development. However, our findings indicate that treatment interventions and outcome measures should also be designed and evaluated for heterotypic development especially in case of increased maternal psychopathology.

Sexual Sadism and Psychopathy in Sexual Homicide Offenders: An Exploration of Their Associates in a Clinical Sample.

Sexual sadism and psychopathy are often considered synonymous with sexual homicide, but there is limited research on their associates in sexual homicide offenders. Associates of dimensional measures of sexual sadism (Sexual Sadism Scale; SeSaS) and psychopathy (Psychopathy Check List-Revised [PCL-R] total, Factor 1, and Factor 2) were examined in 51 male Scottish cases. Over a third were DSM-IV (Diagnostic and Statistical Manual of Mental Disorders-IV) sexual sadists, just under a third screened in with the SeSaS, and a quarter were "Hare psychopaths." Sexual sadism and PCL-R measures were moderately associated. Sexual sadism predicted control, sexual deviance, and unusual behaviour at crime scenes; attempted homicide and having a co-accused; and multiple sexual homicides and previous sexual offending. PCL-R Factor 1 predicted violent, exploitative, and evading detection behaviours at crime scenes; completed homicide; and previous violent offending. PCL-R Factor 2 predicted impulsive behaviours at crime scenes, substance misuse, and previous general offending. Psychopathy and sexual sadism play key roles in sexual homicide, interact with each other, and determine different aspects of offences and offenders.

Irregular eating patterns associate with hypomanic symptoms in bipolar disorders

ABSTRACT Objective: We present novel dimensional methods to describe the timing of eating in psychopathology. We focused on the relationship between current mood in bipolar disorder (BD) and the stability of the temporal pattern of daily eating events. Methods: Consenting BD patients (n = 69) from an outpatient, tertiary care clinic completed hourly charts of mood and eating for two weeks. Mood was also evaluated with Montgomery-Åsberg Depression Rating Scale (MADRS) and Young Mania Rating Scale (YMRS). Results: Illustrative displays, or eatograms, enabling visualization of all recorded eating events were used to guide assessment of the temporal structure of eating across the two week assessment period. We computed indices to quantify irregularities in timing of eating, namely IFRQ, ITIM and IINT for the variability of frequency, timing, and interval of eating events, respectively. In this cohort, irregular temporal pattern of eating correlated with hypomanic symptoms (YMRS with IFRQ, Spearman rank order rh = 0.28, p = .019, with ITIM, rh = 0.44, p < .001, and with IINT rh = 0.38, p = .001), but not depressive symptoms or anthropometric measures. Conclusions: Our data suggest a link between the instability of the temporal order of daily eating and mood. The dimensional measures for eating pattern introduced here enable future investigations of correlations with psychopathology.

Sleep and eating disorders among adults enrolled in a commercial weight loss program: associations with self-report and objective sleep measures.

Some research suggests that eating disorders are related to poor sleep health. To increase knowledge on the relation between sleep and eating disorders, we used a multi-method approach to examine associations between sleep, chronotype, and eating disorder psychopathology. We investigated associations between ED psychopathology, both diagnostic categories (ascertained through self-report data) and dimensional measures, and self-report and ambulatory measures of sleep. Adults currently enrolled in a commercial weight loss program completed self-report measures as well as 1week of ambulatory sleep monitoring and sleep diaries. Participants with full- or sub-threshold bulimia nervosa and binge eating disorder reported significantly lower subjective sleep health and greater eveningness. Additionally, greater severity of eating disorder psychopathology was associated with lower subjective sleep health and greater eveningness. Eating disorder psychopathology was generally not related to objective sleep measures. Regarding diary measures, global eating disorder psychopathology was negatively correlated with subjective reports of feeling rested. Eating disorder psychopathology is associated with participants' subjective sense of sleep quality, but appears to have little relation to objective sleep characteristics. Level of evidence Level V, descriptive study.

Development of a suicide index model in general adolescents using the South Korea 2012\u20132016 national representative survey data

Suicide is a leading cause of death among adolescents and a major public health concern. Here we developed a risk stratification model for adolescent suicide attempts using sociodemographic characteristics, risk behaviours and psychological variables. Participants were 247,222 subjects in the Korea Youth Risk Behavior Web-based Survey (KYRBS). We developed a suicide index based on the suicide risk estimated in the generalized linear model and proposed the risk stratification model using the R language to measure the probability of suicide attempt among adolescents. Among the study population, the annual rate of suicide attempt was approximately 4%. The model provided good prediction for suicide attempt (AUC = 0.85). The important univariate risk factors for the outcome were dimensional measures of age, sex, breakfast consumption, experience of violence, sleep duration, perceived stress, feeling of sadness, current cigarette smoking, current alcohol drinking, perceived general health, perceived academic record, household economic status and living with biological or adoptive parents. Our suicide index model allowed the identification of adolescents who are at a high risk for suicide. This tool may promote the prevention of adolescent suicide and can be particularly useful in everyday settings where it is difficult to contact mental health professionals immediately.

Borderline Personality Disorder Symptom Comorbidity Within a High Externalizing Sample: Relationship to the Internalizing-Externalizing Dimensional Structure of Psychopathology.

Borderline personality disorder (BPD) is highly comorbid with internalizing and externalizing psychopathology. The current study replicates findings indicating that BPD symptomatology is influenced by the distress subfactor of both the internalizing and the externalizing dimension of psychopathology. Confirmatory factor analysis of the covariance of continuous measures of externalizing pathology, internalizing pathology, and BPD symptoms was assessed in 837 young adults. The sample contained a range of externalizing severity from none to high severity, leading to an overrepresentation of externalizing problems. BPD symptoms were associated with both the externalizing dimension and the distress subfactor of the internalizing dimension. Interestingly, BPD had a stronger association with the externalizing dimension than observed in previous studies. Results replicated earlier findings using different and more dimensional measures. Findings indicated that BPD is more heavily influenced by the externalizing dimension of psychopathology within a high externalizing sample, such as those presenting for treatment of alcohol or substance use disorders.

On a decomposition of non-negative Radon measures

We establish a decomposition of non-negative Radon measures on $\mathbb{R}^{d}$ which extends that obtained by Strichartz [6] in the setting of $\alpha $-dimensional measures. As consequences, we deduce some well-known properties concerning the density of non-negative Radon measures. Furthermore, some properties of non-negative Radon measures having their Riesz potential in a Lebesgue space are obtained.

An enhanced cuckoo search using dimension selection

This paper proposes an enhanced cuckoo search algorithm using dimension selection. In the proposed strategy, the dimensional distance measure is used to select a part of dimensions of each solution to search for the new solution in two search components. The dimensions of each solution are selected when those dimensional distances are larger than the average distance of all dimensional distance. A suit of 20 benchmark functions are employed to verify the performance of the proposed algorithm, and the results show the improvement in effectiveness and efficiency of dimension selection.

53 - TRANSLATING DISCOVERIES IN ADHD GENOMICS TO THE CLINIC

Background A recent genome-wide association analysis has identified specific susceptibility variants and a substantial polygenic component for Attention-Deficit/Hyperactivity Disorder (ADHD). Given that emerging risk variants are unlikely to track precisely with conventional diagnoses, whether these discoveries will have utility in clinical settings for improved diagnostics and risk stratification requires further study. Our overall goal is to establish the relevance of emerging psychiatric genetics findings to youth clinical samples. In the current study, we aimed to 1) confirm the convergent validity of ADHD polygenic risk with ADHD-related phenotypes in youth presenting for neuropsychiatric evaluation; and 2) determine the extent to which ADHD polygenic risk associates with phenotypes beyond ADHD that putatively share its underlying liability and have implications for functional outcome. Methods Participants were 470 youth, ages 7 to 18, consecutively referred for neuropsychiatric evaluation and genotyped on the Illumina Infinium PsychArray Beadchip. Diagnoses made subsequent to study enrollment reflected a range of psychopathology and comorbidity. We determined the burden of ADHD-related common variants in these patients at different significance thresholds from the ADHD PGC-iPSYCH meta-analysis. We then associated this polygenic risk with clinical phenotypes. First, we conducted univariate analyses relating ADHD polygenic risks scores (PRSs) to ADHD diagnoses (none/borderline/full) and symptoms, cognition, and dimensional ratings of aggression and mania. Second, we stratified youth by low, medium, and high ADHD polygenic burden and used a mixed modeling approach to determine whether risk strata associated with distinct multivariate clinical profiles. Third, we determined phenotypically distinct latent classes in these and other youth (N~900) based on eight dimensional measures of psychopathology and examined whether the ADHD-PRS discriminated among them. Results The ADHD-PRS predicted the ADHD diagnosis at seven discovery sample thresholds after correction for potential confounds and multiple testing. The strongest association occurred at discovery sample p Discussion In a multi-diagnostic clinical sample, ADHD polygenic risk showed convergent validity with ADHD phenotypes. Genotype- and phenotype-first analyses also indicated that ADHD polygenic burden associates with traits reflecting cognition and behavioral and emotional dysregulation that extend beyond ADHD and that have implications for functional outcome.

SU35 - EVALUATING THE IMPACT OF PHENOTYPIC DEFINITIONS ON STATISTICAL POWER IN MAJOR DEPRESSION GENETICS

Background Obtaining sufficient statistical power has been a key issue in the study of genetics in depression; only recently have samples become large enough to identify any genome-wide significant hits for this phenotype. Researchers have used a range of different approaches to tackle the issue of balancing sample size with phenotypic depth, and here we evaluate the statistical power achieved with these different methods. Methods We collated details of published genome-wide association studies exploring major depression or depressive symptoms. For each study we assessed sampling methods, phenotyping criteria and sample size, and use GPC (Genetics Power Calculator, Purcell et al. 2003) and extension methods (Yang et al. 2010, Traylor et al. 2015) to calculate statistical power, and compare approaches within the literature. We compared the statistical power (as captured by the non-centrality parameter) of each cohort across a range of allele thresholds and genetic effect sizes, contrasting different methodologies of cohort ascertainment within the depression literature. We evaluate how statistical power is affected by the selection of potentially more homogenous but less prevalent depression phenotypes, the potential impact of misclassification in large cohorts which have employed brief phenotypic screening questions, and the value of dimensional measures of depression symptoms in population-based cohorts. Results We confirm the findings of Traylor et al. apply in the case of depression; that in the analysis of specific subtypes of depression performed in datasets including PGC2 (2013, secondary analysis of recurrent, early-onset recurrent and typical-like depression, observed in approximately 75%, 50% and 40% of cases respectively) and CONVERGE (2015, secondary analysis of melancholia observed in approximately 85% of cases), very modest increases in genotypic relative risk (GRR) are required to achieve equivalent power with the whole sample analyses, particularly for less common risk allele frequencies and lower index GRR. We also compare the statistical power of the PGC2 case-control sample (discovery sample n=18,759) and the study from the CHARGE Consortium (discovery sample n= 34,549, Hek et al. 2013) looking at depression symptoms, observing that with a sample size which is 54% of that in CHARGE, the PGC2 dataset has less than half the statistical power to detect genetic effects. Discussion Given range of approaches, here we give evaluation of expected statistical power across a range of approaches specific to the field of major depression genetics. We compare the statistical power achieved in the current literature and evaluate how different phenotypic approaches affect this. If the ultimate aim of our research is to improve outcomes for patients with depression, our phenotypic definitions must be informed by clinical relevance. But nevertheless, an understanding of how statistical power is impacted by these definitions is key to optimal study design for the identification of the genetic variants associated with depressive disorders.

An Integrated Analysis of Neural Network Correlates of Categorical and Dimensional Models of Attention-Deficit/Hyperactivity Disorder

BackgroundAttention-deficit/hyperactivity disorder (ADHD) is a heterogeneous neurodevelopmental disorder, putatively induced by dissociable dysfunctional biobehavioral pathways. Here, we present a proof-of-concept study to parse ADHD-related heterogeneity in its underlying neurobiology by investigating functional connectivity across multiple brain networks to 1) disentangle categorical diagnosis-related effects from dimensional behavior-related effects and 2) functionally map these neural correlates to neurocognitive measures. MethodsWe identified functional connectivity abnormalities related to ADHD across 14 networks within a large resting-state functional magnetic resonance imaging dataset (n = 409; age = 17.5 ± 3.3 years). We tested these abnormalities for their association with the categorical ADHD diagnosis and with dimensional inattention and hyperactivity/impulsivity scores using a novel modeling framework, creating orthogonalized models. Next, we evaluated the relationship of these findings with neurocognitive measures (working memory, response inhibition, reaction time variability, reward sensitivity). ResultsWithin the default mode network, we mainly observed categorical ADHD-related functional connectivity abnormalities, unrelated to neurocognitive measures. Clusters within the visual networks primarily related to dimensional scores of inattention and reaction time variability, while findings within the sensorimotor networks were mainly linked to hyperactivity/impulsivity and both reward sensitivity and working memory. Findings within the cerebellum network and salience network related to both categorical and dimensional ADHD measures and were linked to response inhibition and reaction time variability. ConclusionsThis proof-of-concept study identified ADHD-related neural correlates across multiple functional networks, showing distinct categorical and dimensional mechanisms and their links to neurocognitive functioning.

The Sources of Meaning and Meaning in Life Questionnaire in the Norwegian Context: Relations to Mental Health, Quality of Life, and Self-Efficacy

ABSTRACTThe Sources of Meaning and Meaning in Life Questionnaire (SoMe) offers dimensional measures of meaningfulness, crisis of meaning, and 26 sources of meaning. It allows for a clearer understanding of the variety of existential orientations, which are known to be linked to both mental and physical health. The Norwegian version of the SoMe was validated by testing 925 randomly selected individuals who were representative for the Norwegian population. Reliability scores were satisfactory; factor analyses suggested a 6-factor structure of the sources of meaning scales. Expected patterns of associations with mental health and quality-of-life factors attested the instrument’s construct validity: Meaningfulness showed positive relationships to all quality-of-life factors. There was no relationship with anxiety but negative relationships with depression and distress. Crisis of meaning established a strong positive relationship with anxiety, depression, and distress and a negative relationship with quality-of-life factors. Criterion validity was documented by expected differences in meaningfulness and crisis of meaning between groups with and without presence of depression disorder. Self-efficacy correlated strongly with sources of meaning from the dimension “accomplishment” and moderately negatively with sources of meaning from the dimension “vertical selftranscendence.”

Explaining interpersonal difficulty via implicit and explicit personality correlates of mania risk.

Mania is associated with social conflict, reduced social support, and reduced social interaction quality (Breyer etal., 2003; Coryell etal., 1998; Morriss etal., 2007). Chronic stress in interpersonal relationships is related to the worsening of mood symptoms (Kim etal., 2007), suggesting the importance of characterizing the mechanism of interpersonal relationship disruption in bipolar disorder. The current study was designed to investigate exaggerated dominance tendencies present in at-risk individuals (Gardner, 1982; Wilson and Price, 2006), which may represent one such mechanism. Sixty-nine University undergraduate participants (50.7% female, 22 categorized as high mania risk) completed an implicit measure of power motivation and series of self-report questionnaires designed to assess dominance-relevant traits. Risk for mania was related to a tendency to experience contempt, and an implicit index of dominance tendencies, and also to trait-like tendencies to experience pride, perceptions of being more powerful and influential across relationships,. Use of an undergraduate population and a dimensional measure of mania risk (rather than diagnosed individuals) are limitations. Mania risk is tied not only to the pursuit of dominance, but also to beliefs and actions consistent with a sense of power. Current findings provide evidence that the dominance system profile observed in those at risk for mania could be one source of interpersonal problems.

An infinite dimensional purification principle without saturation

We establish a purification process for the min-expected utilities coming from economy theory, involved in the phenomenon of aversion to the ambiguity in game and decision theories. We use instead of the saturation property a characterization of Lyapunov infinite dimensional vector measures established in “G. Knowles, Lyapunov vector measures, SIAM J. Control 13 (1975) 294–303”.

Plasma levels of leptin and adiponectin and depressive symptoms in young adults

Circulating levels of adipokines are known to be associated with depression. This study aimed to investigate a possible association between leptin, adiponectin and dimensional measures of depressive symptoms in young adults with and without psychiatric illness. Total plasma adiponectin and leptin levels were measured in 194 young adults seeking psychiatric ambulatory care and 57 healthy controls. Depressive symptoms were assessed using the Montgomery-Åsberg Depression Self-Rating Scale (MADRS-S). Analysis was performed on men and women separately. P-leptin levels were significantly elevated in patients compared with controls and correlated with total MADRS-S scores in the women. Women with P-leptin in the highest quartile reached a significantly higher MADRS-S score than women in the lowest quartile, but this difference disappeared after adjusting for body mass index (BMI) and antidepressant use. MADRS-S score was associated with P-leptin in female patients without antidepressant use, independently of BMI. There was no association between P-leptin levels and current major depression. P-adiponectin levels were not associated with depressive symptoms or current major depression. The findings indicate that P-leptin levels are associated with depressive symptom severity in young women; however, the association is linked to other factors, which challenges its usefulness as a biomarker for depression in clinical psychiatry.

Dimensions of Anxiety, Age, and Gender: Assessing Dimensionality and Measurement Invariance of the State-Trait for Cognitive and Somatic Anxiety (STICSA) in an Italian Sample.

The State–Trait Inventory for Cognitive and Somatic Anxiety (STICSA) is a widely used measure of state and trait anxiety that permits a specific assessment of cognitive and somatic anxiety. Previous research provided inconsistent findings about its factor structure in non-clinical samples (e.g., hierarchical or bi-factor structure). To date, no psychometric validation of the Italian version of the STICSA has been conducted. Our study aimed to determine the psychometric functioning of the Italian version of the STICSA, including its dimensionality, gender and age measurement equivalence, and convergent/divergent validity in a large sample of community-dwelling participants (N = 2,938; 55.9% female). Through confirmatory factor analysis, the multidimensional structure of both State and Trait STICSA scales, with each including Cognitive and Somatic dimensions, was supported. Factor structure invariance was tested and established at configural, metric, and scalar levels for males and females. Additionally, full factorial measurement invariance was supported for the State scale across young, middle age, and old adult groups whereas the Trait scale was partially invariant across age groups. The STICSA also showed good convergent validity with concurrent anxiety measures (State-Trait Anxiety Inventory and Beck Anxiety Inventory), and satisfactory internal discriminant validity with two depression measures (Teate Depression Inventory and Beck Depression Inventory-II). Results provided support for the multidimensionality of the STICSA, as well as the generalizability of the State and Trait scales as independent measures of Cognitive and Somatic symptomatology across gender in the general population. Implications for research and personality and clinical assessment are discussed.

Dimensional Complexity of the Resting Brain in Healthy Aging, Using a Normalized MPSE.

Spontaneous fluctuations of resting-state functional connectivity have been studied in many ways, but grasping the complexity of brain activity has been difficult. Dimensional complexity measures, which are based on Eigenvalue (EV) spectrum analyses (e.g., Ω entropy) have been successfully applied to EEG data, but have not been fully evaluated on functional MRI recordings, because only through the recent introduction of fast multiband fMRI sequences, feasable temporal resolutions are reached. Combining the Eigenspectrum normalization of Ω entropy and the scalable architecture of the so called Multivariate Principal Subspace Entropy (MPSE) leads to a new complexity measure, namely normalized MPSE (nMPSE). It allows functional brain complexity analyses at varying levels of EV energy, independent from global shifts in data variance. Especially the restriction of the EV spectrum to the first dimensions, carrying the most prominent data variance, can act as a filter to reveal the most discriminant factors of dependent variables. Here we look at the effects of healthy aging on the dimensional complexity of brain activity. We employ a large open access dataset, providing a great number of high quality fast multiband recordings. Using nMPSE on whole brain, regional, network and searchlight approaches, we were able to find many age related changes, i.e., in sensorimotoric and right inferior frontal brain regions. Our results implicate that research on dimensional complexity of functional MRI recordings promises to be a unique resource for understanding brain function and for the extraction of biomarkers.

Intrinsic functional connectivity correlates of person-level risk for bipolar disorder in offspring of affected parents.

Offspring of parents with bipolar disorder (OBP) are at increased risk to develop bipolar disorder (BD). Alterations in resting-state functional connectivity (rsFC) have been identified in OBP; however, replication has been limited and correlation with person-level risk is unknown. A recent study found reduced rsFC between left inferior frontal gyrus (IFG) and clusters in the left insula (LINS), lentiform nucleus (LENT), and midcingulate cortex (MCING) in OBP (Roberts et al. 2017); here, we aim to extend these findings to at-risk youth. We scanned a subset of the Pittsburgh Bipolar Offspring Study, a longitudinal study of OBP and community controls. Twenty-four OBP, 20 offspring of control parents with non-bipolar psychopathology (OCP), and 27 healthy controls (HC) had acceptable rsFC data. After preprocessing steps, we assessed group differences in seed-based rsFC between the IFG and target clusters (LINS, LENT, MCING) using multivariate regression. Next, we tested whether rsFC correlated with person-level risk score and with other dimensional measures. We did not find group differences in rsFC between IFG and target regions. Within OBP, risk score negatively correlated with IFG-LINS rsFC (p = 0.002). Across groups, mood lability correlated negatively with rsFC between IFG and target regions (p = 0.0002), due to negative correlation with IFG-LINS (p = 0.0003) and IFG-MCING (p = 0.001) rsFC. While group-level differences were not replicated, IFG-LINS rsFC was negatively correlated with a person-level risk score in OBP and with mood lability (a predictor of BD) across the sample. Thus, IFG-LINS rsFC might constitute a risk marker, within OBP, for the development of BD.

A data mining and item response mixture modeling method to retrospectively measure Diagnostic and Statistical Manual of Mental Disorders-5 attention deficit hyperactivity disorder in the 1970 British Cohort Study.

To facilitate future outcome studies, we aimed to develop a robust and replicable method for estimating a categorical and dimensional measure of Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) attention deficit hyperactivity disorder (ADHD) in the 1970 British Cohort Study (BCS70). Following a data mining framework, we mapped DSM-5 ADHD symptoms to age 10 BCS70 data (N=11,426) and derived a 16-item scale (α=0.85). Mapping was validated by an expert panel. A categorical subgroup was derived (n=594, 5.2%), and a zero-inflated item response theory (IRT) mixture model fitted to estimate a dimensional measure. Subgroup composition was comparable with other ADHD samples. Relative risk ratios (ADHD/not ADHD) included boys=1.38, unemployed fathers=2.07, below average reading=2.58, and depressed parent=3.73. Our estimated measures correlated with two derived reference scales: Strengths and Difficulties Questionnaire hyperactivity (r=0.74) and a Rutter/Conners-based scale (r=0.81), supporting construct validity. IRT model items (symptoms) had moderate to high discrimination (0.90-2.81) and provided maximum information at average to moderate theta levels of ADHD (0.5-1.75). We extended previous work to identify ADHD in BCS70, derived scales from existing data, modeled ADHD items with IRT, and adjusted for a zero-inflated distribution. Psychometric properties were promising, and this work will enable future studies of causal mechanisms in ADHD.

Inferior Frontal Gyrus Volume Loss Distinguishes Between Autism and (Comorbid) Attention-Deficit/Hyperactivity Disorder-A FreeSurfer Analysis in Children.

Objective: Autism spectrum (ASD) and attention-deficit/hyperactivity disorder (ADHD) are neurodevelopmental disorders with a high rate of comorbidity. To date, diagnosis is based on clinical presentation and distinct reliable biomarkers have been identified neither for ASD nor ADHD. Most previous neuroimaging studies investigated ASD and ADHD separately.Method: To address the question of structural brain differences between ASD and ADHD, we performed FreeSurfer analysis in a sample of children with ADHD (n = 30), with high-functioning ASD (n = 14), with comorbid high-functioning ASD and ADHD (n = 15), and of typically developed controls (TD; n = 36). With FreeSurfer, an automated brain imaging processing and analyzing suite, we reconstructed the cerebral cortex and calculated gray matter volumes as well as cortical surface parameters in terms of cortical thickness and mean curvature.Results: A significant main effect of the factor ADHD was detected for the left inferior frontal gyrus (Pars orbitalis) volume, with the ADHD group exhibiting smaller Pars orbitalis volumes. Dimensional measures of autism (SRS total raw score) and ADHD (DISYPS-II FBB-ADHD score) had no significant influence on the left Pars orbitalis volume. Both, ASD and ADHD tended to have an effect on cortical thickness or mean curvature, which did not survive correction for multiple comparisons.Conclusion: Our results underline that ADHD rather than ASD is associated with volume loss in the left inferior frontal gyrus (Pars orbitalis). This area might play a relevant role in modulating symptoms of inattention and/or impulsivity in ADHD. The effect of comorbid ADHD in ASD samples and vice versa, on cortical thickness and mean curvature, requires further investigation in larger samples.