Familial co-aggregation and shared familiality among neurodevelopmental problems and with aggressive behavior,...

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 (λ_R) 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 (λ_R = 2.40-4.04; f² = 0.22-0.39). The familial co-aggregation and shared familiality among neurodevelopmental problems (λ_R = 1.39-2.56; r_F = 0.52-0.94), and with aggressive behavior (λ_R = 1.79-2.56; r_F = 0.60-0.78), depression (λ_R = 1.45-2.29; r_F = 0.43-0.76), and anxiety (λ_R = 1.44-2.31; r_F = 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 (λ_R = 0.53-1.57; r_F = -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.