Exposure to adversities in early childhood is associated with psychotic experiences and disorders in adulthood. We aimed to examine whether early childhood adversities are associated with middle childhood psychotic experiences in a cohort of children at familial high risk of schizophrenia (FHR-SZ), bipolar disorder (FHR-BP) and population-based controls (controls).

Four hundred and forty-six children from The Danish High Risk and Resilience Study – VIA7 and VIA11 participated in this study (FHR-SZ = 170; FHR-BP = 103; controls = 173). Exposure to early childhood adversities and psychotic experiences were assessed using face-to-face interviews. Having childhood adversities assessed at baseline (age 7) was used as predictor. Psychotic experiences assessed at follow-up (age 11) were used as outcome.

Across the sample, exposure to early childhood interpersonal adversities was associated with an increased risk for any middle childhood psychotic experiences and subclinical delusions when adjusting for relevant confounders (OR 1.8, 95% CI 1.0–3.1, p = 0.05; OR 3.0, 95% CI 1.6–5.6, p < 0.001). There was no significant dose–response effect of exposure to multiple types of childhood adversities on any psychotic experiences. There were no interaction effects between early childhood adversities and FHR on middle childhood psychotic experiences. Exploratory analyses revealed that experiencing domestic violence in early childhood was associated with any middle childhood psychotic experiences (OR 2.8, 95% CI 1.5–5.1, p = 0.001).

Exposure to interpersonal adversities during early childhood is associated with an increased risk for middle childhood psychotic experiences including specifically subclinical delusions. Future studies should examine associations between exposure to childhood adversities and conversion to psychosis within this cohort.

Psychiatric disorders are highly polygenic and show patterns of partner resemblance. Partner resemblance has direct population-level genetic implications if it is caused by assortative mating, but not if it is caused by convergence or social homogamy. Using genetics may help distinguish these different mechanisms. Here, we investigated whether partner resemblance for schizophrenia and bipolar disorder is influenced by assortative mating using polygenic risk scores (PRSs).

PRSs from The Danish High-Risk and Resilience Study—VIA 7 were compared between parents in three subsamples: population-based control parent pairs (N=198), parent pairs where at least one parent had schizophrenia (N=193), and parent pairs where at least one parent had bipolar disorder (N=115).

The PRS for schizophrenia was predictive of schizophrenia in the full sample and showed a significant correlation between parent pairs (r=0.121, p=0.0440), indicative of assortative mating. The PRS for bipolar disorder was also correlated between parent pairs (r=0.162, p=0.0067), but it was not predictive of bipolar disorder in the full sample, limiting the interpretation.

Our study provides genetic evidence for assortative mating for schizophrenia, with important implications for our understanding of the genetics of schizophrenia.

Sex differences in brain structure and neurodevelopment occur in non-clinical populations. We investigated whether sex had a similar effect on developmental domains amongst boys and girls with a familial risk of schizophrenia (FHR-SZ), bipolar disorder (FHR-BP), and controls.

Through Danish registries, we identified 522 7-year-old children (242 girls) with FHR-SZ, FHR-BP, and controls. We assessed their performance within the domains of neurocognition, motor function, language, social cognition, social behavior, psychopathology, and home environment.

FHR-SZ boys compared with FHR-SZ girls had a higher proportion of disruptive behavior and attention-deficit hyperactivity disorder (ADHD) and exhibited lower performance in manual dexterity, balance, and emotion recognition. No sex differences were found between boys and girls within FHR-BP group. Compared with controls, both FHR-SZ boys and FHR-SZ girls showed impaired processing speed and working memory, had lower levels of global functioning, and were more likely to live in an inadequate home environment. Compared with control boys, FHR-SZ boys showed impaired manual dexterity, social behavior, and social responsiveness, and had a higher proportion of ADHD and disruptive behavior disorder diagnoses. Stress and adjustment disorders were more common in FHR-BP boys compared with control boys. We found no differences between FHR-BP girls and control girls.

Impairment within neurodevelopmental domains associated within FHR-SZ boys v. FHR-SZ girls was most evident among boys, whereas no sex differences were found within the FHR-BP group (FHR-BP boys v. FHR-BP girls). FHR-SZ boys exhibited the highest proportion of early developmental impairments.

The home environment has a major impact on child development. Parental severe mental illness can pose a challenge to the home environment of a child. We aimed to examine the home environment of children of parents with schizophrenia or bipolar disorder and controls longitudinally through at-home assessments.

Assessments were conducted within The Danish High Risk and Resilience Study, a nationwide multi-center cohort study of children of parents with schizophrenia or bipolar disorder and population-based controls. The level of at-home stimulation and support was measured at age 7 (N = 508 children) and age 11 (N = 430 children) with the semi-structured HOME Inventory. Results from the 11-year follow-up study were analyzed and compared with 7-year baseline results to examine change across groups.

At age 11, children of parents with schizophrenia and bipolar disorder had lower levels of stimulation and support than controls (mean (s.d.) = 46.16 (5.56), 46.87 (5.34) and 49.25 (4.37) respectively, p < 0.001). A higher proportion of children with parental schizophrenia or bipolar disorder lived in inadequate home environments at age 11, compared with controls (N (%) = 24 (15.0), 12 (12.2) and 6 (3.5) respectively, p < 0.003). The changes in home environment scores did not differ across groups from age 7 to age 11.

Assessed longitudinally from the children's age of 7 to 11, children of parents with schizophrenia or bipolar disorder had lower levels of stimulation and support in their homes than controls. Integrated support which can target practical, economic, social and health issues to improve the home environment is indicated.