Psychiatric disorders and type 2 diabetes mellitus (T2DM) are heritable, polygenic, and often comorbid conditions, yet knowledge about their potential shared familial risk is lacking. We used family designs and T2DM polygenic risk score (T2DM-PRS) to investigate the genetic associations between psychiatric disorders and T2DM.

We linked 659 906 individuals born in Denmark 1990–2000 to their parents, grandparents, and aunts/uncles using population-based registers. We compared rates of T2DM in relatives of children with and without a diagnosis of any or one of 11 specific psychiatric disorders, including neuropsychiatric and neurodevelopmental disorders, using Cox regression. In a genotyped sample (iPSYCH2015) of individuals born 1981–2008 (n = 134 403), we used logistic regression to estimate associations between a T2DM-PRS and these psychiatric disorders.

Among 5 235 300 relative pairs, relatives of individuals with a psychiatric disorder had an increased risk for T2DM with stronger associations for closer relatives (parents:hazard ratio = 1.38, 95% confidence interval 1.35–1.42; grandparents: 1.14, 1.13–1.15; and aunts/uncles: 1.19, 1.16–1.22). In the genetic sample, one standard deviation increase in T2DM-PRS was associated with an increased risk for any psychiatric disorder (odds ratio = 1.11, 1.08–1.14). Both familial T2DM and T2DM-PRS were significantly associated with seven of 11 psychiatric disorders, most strongly with attention-deficit/hyperactivity disorder and conduct disorder, and inversely with anorexia nervosa.

Our findings of familial co-aggregation and higher T2DM polygenic liability associated with psychiatric disorders point toward shared familial risk. This suggests that part of the comorbidity is explained by shared familial risks. The underlying mechanisms still remain largely unknown and the contributions of genetics and environment need further investigation.

An association between psychiatric disorders in childhood and the later development of major depressive disorders (MDD) has been suggested. However, no prospective population-based cohort study has been able to directly compare the risks of MDD following a broad spectrum of child and adolescent psychiatric disorders.

To use a large, register-based cohort to establish whether or not psychiatric disorders in childhood lead to a higher risk of later MDD and, if so, which disorders are associated with the highest risks.

To estimate and compare the risk of later MDD in children diagnosed with one of ten psychiatric disorders

Using Danish population-based registers all persons born in Denmark from 1990 through 2000 were identified and followed from their 5^th birthday through 2012. Cumulative incidences and incidence rate ratios of MDD following each of ten exposure disorders were calculated

We followed 960,026 persons, contributing 8,778,331 person-years. Among these 7,787 were diagnosed with MDD (incidence=1.7/1000 pyrs).

Diagnosis of any psychiatric disorder led to an absolute risk of MDD within eight years of 1.6% in males and 4.98% in females with early onset (ages 0-14) and 7.02% in males and 15.98% in females with late onset (ages 14-18).

For all groups, anxiety and eating disorders were associated with the highest risks of MDD.

Most disorders were associated with a significantly increased risk of later MDD and children with anxiety and eating disorders carry the greater risk. Future research should focus on common pathways between depression and other psychiatric disorders.

To estimate the risk of schizophrenia in adulthood among children and adolescents with ADHD compared to the background population.

Two hundred and eight youths with ADHD (183 boys; 25 girls) were followed prospectively. Diagnoses of schizophrenia were obtained from The Danish Psychiatric Central Register. The relative risk (RR) of schizophrenia for cases with ADHD, compared to the normal population, was calculated as risk ratios. Hazard ratios (HR's) by Cox regression were calculated in the predictor analyses.

Mean age for ADHD cases at follow-up was 31.1 years. Schizophrenia diagnoses were given to 3.8% of these cases. Compared to the general population, RR of schizophrenia in cases with ADHD was 4.3 (95% CI 1.9–8.57).

This prospective follow-up study found children with ADHD to be at higher risk of later schizophrenia than controls. If replicated, these results warrant increased focus on the possible emergence symptoms of schizophrenia or schizophreniform psychosis during clinical follow-up of patients with ADHD.

In addition to problems with inattention and hyperactivity, children with ADHD show poor organizational skills required for managing time and materials in academic projects. Poor organizational skills are associated with academic underachievement as well as psychosocial, occupational and economic difficulties. Behavioral approaches for ADHD are effective in reducing hyperactivity symptoms and behavioral problems, but the effects on academic functioning have been modest. An increasing emphasis on treatment of organizational skills has emerged in recent years, as difficulties with time management and organization of materials tend to persist and increase with age despite medication and behavioral treatments.

The primary objective is to investigate whether organizational skills training has a positive effect on organizational skills. The secondary and exploratory objectives are to investigate the effect on ADHD symptoms, adaptive functioning, academic performance and cognitive functions with a 24 weeks follow up.

Our goal is to provide cost-effective group-based treatment for children with ADHD and their parents. This will be the first randomized and controlled trial of organizational skills in Denmark.

Participants are included in two sites in Southern Denmark and will be randomized to Organizational skills training or treatment as usual. Organizational skills training will be provided in a group format for children and parents over 10 weeks.

Perspectives Given the strong association between organizational skills and functional outcome, it is very important to address organizational skills in children and adolescents with ADHD as organizational skills deficits hinder the academic performance of even gifted students with ADHD and increase with age.

The authors have not supplied their declaration of competing interest.

Cannabis use and cannabis use disorder (CUD) is increased in patients with schizophrenia. It is important to establish if this is explained by non-causal factors, such as shared genetic vulnerability. We aimed to investigate whether the polygenic risk scores (PRS) for schizophrenia and other psychiatric disorders would predict CUD in controls, patients with schizophrenia, and patients with other psychiatric disorders.

We linked nationwide Danish registers and genetic information obtained from dried neonatal bloodspots in an observational analysis. We included people with schizophrenia, other psychiatric disorders, and controls. The exposures of interest were the PRS for schizophrenia, attention-deficit hyperactivity disorder (ADHD) autism spectrum disorder, and anorexia nervosa. The main outcome of interest was the diagnosis of CUD.

The study included 88 637 individuals. PRS for schizophrenia did not predict CUD in controls [hazard ratio (HR) = 1.16, 95% CI 0.95–1.43 per standard-deviation increase in PRS, or HR = 1.47, 95% CI 0.72–3.00 comparing highest v. remaining decile], but PRS for ADHD did (HR = 1.27, 95% CI 1.08–1.50 per standard-deviation increase, or HR = 2.02, 95% CI 1.27–3.22 for the highest decile of PRS). Among cases with schizophrenia, the PRS for schizophrenia was associated with CUD. While CUD was a strong predictor of schizophrenia (HR = 4.91, 95% CI 4.36–5.53), the inclusion of various PRS did not appreciably alter this association.

The PRS for schizophrenia was not associated with CUD in controls or patients with other psychiatric disorders than schizophrenia. This speaks against the hypothesis that shared genetic vulnerability would explain the association between cannabis and schizophrenia.

Persons diagnosed with attention-deficit hyperactivity disorder (ADHD) have been found to have an increased risk of suicidal behaviour, but the pathway remains to be thoroughly explored.

To determine whether persons with ADHD are more likely to present with suicidal behaviour (i.e. suicide attempts and deaths by suicide) if they have a comorbid psychiatric disorder.

Using nationwide registers covering the entire population of Denmark, this cohort study of 2.9 million individuals followed from 1 January 1995 until 31 December 2014, covers more than 46 million person-years. All persons aged ≥10 years with Danish-born parents were identified and persons with a diagnosis of ADHD were compared with persons without. Incidence rate ratios (IRRs) were calculated by Poisson regression, with adjustments for sociodemographics and parental suicidal behaviour.

Persons with ADHD were followed for 164 113 person-years and 697 suicidal outcomes were observed. This group was found to have an IRR of suicidal behaviour of 4.7 (95% CI, 4.3–5.1) compared with those without ADHD. Persons with ADHD only had a 4.1-fold higher rate (95% CI, 3.5–4.7) when compared with those without any psychiatric diagnoses. For persons with ADHD and comorbid disorders the IRR was higher yet (IRR: 10.4; 95% CI, 9.5–11.4).

This study underlines the link between ADHD and an elevated rate of suicidal behaviour, which is significantly elevated by comorbid psychiatric disorders. In sum, these results suggest that persons with ADHD and comorbid psychiatric disorders are targets for suicide preventive interventions.

None.