To refine the knowledge on familial transmission, we examined the (shared) familial components among neurodevelopmental problems (i.e. two attention-deficit/hyperactivity–impulsivity disorder [ADHD] and six autism spectrum disorder [ASD] subdomains) and with aggressive behavior, depression, anxiety, and substance use.

Data were obtained from a cross-sectional study encompassing 37 688 participants across three generations from the general population. ADHD subdomains, ASD subdomains, aggressive behavior, depression, anxiety, and substance use were assessed. To evaluate familial (co-)aggregation, recurrence risk ratios (λR) were estimated using Cox proportional hazards models. The (shared) familiality (f2), which is closely related to (shared) heritability, was assessed using residual maximum likelihood-based variance decomposition methods. All analyses were adjusted for sex, age, and age2.

The familial aggregation and familiality of neurodevelopmental problems were moderate (λR = 2.40–4.04; f2 = 0.22–0.39). The familial co-aggregation and shared familiality among neurodevelopmental problems (λR = 1.39–2.56; rF = 0.52–0.94), and with aggressive behavior (λR = 1.79–2.56; rF = 0.60–0.78), depression (λR = 1.45–2.29; rF = 0.43–0.76), and anxiety (λR = 1.44–2.31; rF = 0.62–0.84) were substantial. The familial co-aggregation and shared familiality between all neurodevelopmental problems and all types of substance use were weak (λR = 0.53–1.57; rF = −0.06–0.35).

Neurodevelopmental problems belonging to the same disorder were more akin than cross-disorder problems. That said, there is a clear (shared) familial component to neurodevelopmental problems, in part shared with other psychiatric problems (except for substance use). This suggests that neurodevelopmental disorders, disruptive behavior disorders, and internalizing disorders share genetic and environmental risk factors.