The contribution of genetic factors to obsessive-compulsive (OC) symptoms has not been examined using a large population-based sample of adults. Furthermore, the extent to which there are qualitative and quantitative differences in genetic architecture between men and women with OC symptoms has not been elucidated.

We obtained the Young Adult Self Report Obsessive-Compulsive Scale (YASR-OCS) from a group of 5893 monozygotic (MZ) and dizygotic (DZ) twins, and 1304 additional siblings from the population-based Netherlands Twin Register. Structural equation modelling was used to decompose the variation in OC behaviour into genetic and environmental components and analyse quantitative and qualitative sex differences.

Familial resemblance was the same for DZ twins and non-twin siblings, which means that there was no evidence for a special twin environment. The same genetic risk factors for OC behaviour were expressed in men and women. Depending on the choice of fit index, we found small (39% for men and 50% for women) or no sex differences (47% for both men and women) in heritability. The remaining variance in liability was due to individual-specific environment.

OC behaviour showed a moderate heritability. At most, small quantitative sex differences were found in the genetic architecture of OC behaviour, and no qualitative sex differences.

Depression and anxiety in Parkinson's disease are common and frequently co-morbid, with significant impact on health outcome. Nevertheless, management is complex and often suboptimal. The existence of clinical subtypes would support stratified approaches in both research and treatment.

Five hundred and thirteen patients with Parkinson's disease were assessed annually for up to 4 years. Latent transition analysis (LTA) was used to identify classes that may conform to clinically meaningful subgroups, transitions between those classes over time, and baseline clinical and demographic features that predict common trajectories.

In total, 64.1% of the sample remained in the study at year 4. LTA identified four classes, a ‘Psychologically healthy’ class (approximately 50%), and three classes associated with psychological distress: one with moderate anxiety alone (approximately 20%), and two with moderate levels of depression plus moderate or severe anxiety. Class membership tended to be stable across years, with only about 15% of individuals transitioning between the healthy class and one of the distress classes. Stable distress was predicted by higher baseline depression and psychiatric history and younger age of onset of Parkinson's disease. Those with younger age of onset were also more likely to become distressed over the course of the study.

Psychopathology was characterized by relatively stable anxiety or anxious-depression over the 4-year period. Anxiety, with or without depression, appears to be the prominent psychopathological phenotype in Parkinson's disease suggesting a pressing need to understanding its mechanisms and improve management.

Bipolar disorder (BD) has been associated with altered brain structural and functional connectivity. However, little is known regarding alterations of the structural brain connectome in BD. The present study aimed to use diffusion-tensor imaging (DTI) and graph theory approaches to investigate the rich club organization and white matter structural connectome in BD.

Forty-two patients with unmedicated BD depression and 59 age-, sex- and handedness-matched healthy control participants underwent DTI. The whole-brain structural connectome was constructed by a deterministic fiber tracking approach. Graph theory analysis was used to examine the group-specific global and nodal topological properties, and rich club organizations, and then nonparametric permutation tests were used for group comparisons of network parameters.

Compared with healthy control participants, the patients with BD showed abnormal global properties, including increased characteristic path length, and decreased global efficiency and local efficiency. Locally, the patients with BD showed abnormal nodal parameters (nodal strength, nodal efficiency, and nodal betweenness) predominantly in the parietal, orbitofrontal, occipital, and cerebellar regions. Moreover, the patients with BD showed decreased rich club and feeder connectivity density.

Our results may reflect the disrupted white matter topological organization in the whole-brain, and abnormal regional connectivity supporting cognitive and affective functioning in depressed BD, which, in part, be due to impaired rich club connectivity.

Despite its importance as a public health concern, relatively little is known about the natural course of cannabis use disorders (CUDs). The primary objective of this research was to provide descriptive data on the onset, recovery and recurrence functions of CUDs during the high-risk periods of adolescence, emerging adulthood and young adulthood based on data from a large prospective community sample.

Probands (n = 816) from the Oregon Adolescent Depression Project (OADP) participated in four diagnostic assessments (T1–T4) between the ages of 16 and 30 years, during which current and past CUDs were assessed.

The weighted lifetime prevalence of CUDs was 19.1% with an average onset age of 18.6 years. Although gender was not significantly related to the age of initial CUD onset, men were more likely to be diagnosed with a lifetime CUD. Of those diagnosed with a CUD episode, 81.8% eventually achieved recovery during the study period. Women achieved recovery significantly more quickly than men. The recurrence rate (27.7%) was relatively modest, and most likely to occur within the first 36 months following the offset of the first CUD episode. CUD recurrence was uncommon after 72 months of remission and recovery.

CUDs are relatively common, affecting about one out of five persons in the OADP sample prior to the age of 30 years. Eventual recovery from index CUD episodes is the norm, although about 30% of those with a CUD exhibit a generally persistent pattern of problematic use extending 7 years or longer.

Numerous epidemiological studies have reported a positive association between major depression (MD) and regular tobacco use (RU) or nicotine dependence (ND). However, few have used a genetically informative design to assess whether these traits share a common genetic and/or environmental liability.

We assessed MD, RU and ND in same-sex twins from the population-based Swedish Twin Registry. In males, we examined both cigarette use and snus (smokeless tobacco) use. We used structural equation modeling to examine the relationship between MD, RU, and ND given RU.

The results suggest modest correlations between MD and RU, and between MD and ND. In males, the liability shared between MD and RU is solely genetic for both cigarettes and snus, while MD and ND share both genetic and unique environmental influences. The continuation to ND given RU differed considerably between cigarette and snus users. In females, both MD–RU and MD–ND relationships are partially attributable to genetic and unique environmental correlations.

The relationship among MD, RU and ND is at least partially attributable to shared genetic and environmental risk factors. The genetic and environmental correlations between traits are modest. The nature of the shared liability differs by sex, and in males, by the type of tobacco product used. Differences between previous reports and results presented in the current study are suggestive of population differences in how MD and tobacco use inter-relate.

We investigated work-related exposure to stressful and traumatic events in police officers, including repeated exposure to traumatic materials, and predicted that ICD-11 complex PTSD (CPTSD) would be more prevalent than posttraumatic stress disorder (PTSD). The effects of demographic variables on exposure and PTSD were examined, along with whether specific types of exposure were uniquely associated with PTSD or CPTSD.

An online survey covering issues about trauma management, wellbeing and working conditions was disseminated via social media and official policing channels throughout the UK. In total, 10 401 serving police officers self-identified as having been exposed to traumatic events. Measurement of PTSD and CPTSD utilised the International Trauma Questionnaire.

The prevalence of PTSD was 8.0% and of CPTSD was 12.6%. All exposures were associated with PTSD and CPTSD in bivariate analyses. Logistic regression indicated that both disorders were more common in male officers, and were associated independently with frequent exposure to traumatic incidents and traumatic visual material, and with exposure to humiliating behaviours and sexual harassment, but not to verbal abuse, threats or physical violence. Compared to PTSD, CPTSD was associated with exposure to humiliating behaviours and sexual harassment, and also with lower rank and more years of service.

CPTSD was more common than PTSD in police officers, and the data supported a cumulative burden model of CPTSD. The inclusion in DSM-5 Criterion A of work-related exposure to traumatic materials was validated for the first time. Levels of PTSD and CPTSD mandate enhanced occupational mental health services.

There is an appreciable overlap in the clinical presentation, epidemiology and treatment response of the two major psychotic disorders – schizophrenia and bipolar disorder. Nevertheless, the shared neurobiological correlates of these two disorders are still elusive. Using diffusion tensor imaging (DTI), we sought to identify brain regions which share altered white-matter connectivity across a clinical spectrum of psychotic disorders.

A sample of 41 healthy controls, 62 patients in a clinically stable state of an established psychotic disorder (40 with schizophrenia, 22 with bipolar disorder) were studied using DTI. Tract-based spatial statistics (TBSS) was used in order to study group differences between patients with psychosis and healthy controls using fractional anisotropy (FA). Probabilistic tractography was used in order to visualize the clusters that showed significant differences between these two groups.

The TBSS analysis revealed five clusters (callosal, posterior thalamic/optic, paralimbic, fronto-occipital) with reduced FA in psychosis. This reduction in FA was associated with an increase in radial diffusivity and a decrease in mode of anisotropy. Factor analysis revealed a single white-matter integrity factor that predicted social and occupational functioning scores in patients irrespective of the diagnostic categorization.

Our results show that a shared white-matter dysconnectivity links the two major psychotic disorders. These microstructural abnormalities predict functional outcome better than symptom-based diagnostic boundaries during a clinically stable phase of illness, highlighting the importance of seeking shared neurobiological factors that underlie the clinical spectrum of psychosis.

Attention deficit hyperactivity disorder (ADHD) shows a strong phenotypic and genetic association with reaction time (RT) variability, considered to reflect lapses in attention. Yet we know little about whether this aetiological pathway is shared with other affected cognitive processes in ADHD, such as lower IQs or the generally slower responses (mean RTs). We aimed to address the question of whether a shared set of genes exist that influence RT variability, mean RT, IQ and ADHD symptom scores, or whether there is evidence of separate aetiological pathways.

Multivariate structural equation modelling on cognitive tasks data (providing RT data), IQ and ADHD ratings by parents and teachers collected on general population sample of 1314 twins, at ages 7–10 years.

Multivariate structural equation models indicated that the shared genetic influences underlying both ADHD symptom scores and RT variability are also shared with those underlying mean RT, with both types of RT data largely indexing the same underlying liability. By contrast, the shared genetic influences on ADHD symptom scores and RT variability (or mean RT) are largely independent of the genetic influences that ADHD symptom scores share with IQ.

The finding of unique aetiological pathways between IQ and RT data, but shared components between mean RT, RT variability and ADHD symptom scores, illustrates key influences in the genetic architecture of the cognitive and energetic processes that underlie the behavioural symptoms of ADHD. In addition, the multivariate genetic model fitting findings provide valuable information for future molecular genetic analyses.

Personality disorder (PD) in psychosis is poorly studied. As PD can affect outcome in mental disorders, it is important to understand its prevalence in order to plan services, understand prognosis more fully and maximize management options.

Literature searching revealed 3972 potential papers. Twenty papers including 6345 patients were included in the final analysis. There was great variation in prevalence and multilevel modelling was used to identify possible reasons for this heterogeneity.

The prevalence of PD varied from 4.5% to 100%. Multilevel analysis suggested country of study, study type, the instruments used to diagnose PD and patient care correlated with the prevalence data explaining the study level heterogeneity, with 34.2, 33.4, 17.0 and 4.5% by each variable respectively. Personality studies in Canada and Sweden reported lower PD prevalence, whereas in Spain it was higher than the multinational study. Compared with randomized controlled trials, case-control studies reported lower prevalence [odds ratio (OR)=0.35, 95% confidence interval (CI) 0.15–0.79] and observational studies higher prevalence (OR 70.5, 95% CI 8.5–583). Primary-care patients were less likely to be diagnosed (OR 0.02, 95% CI 0–0.19) than hospital patients, and out-patients had higher prevalence (OR 12.5, 95% CI 1.77–88.6).

The reported prevalence of PD in schizophrenia varies significantly. Statistical modelling suggests care, country, study type and diagnostic tools for PD all bias prevalence rates. The number of papers reaching the inclusion criteria, the relative paucity of information and the difficulties in developing an accurate statistical model limited interpretation from the study.