Developmental Contributions of Schizophrenia Risk Alleles and Childhood Peer Victimization to Early-Onset Mental Health Trajectories

Objective. Twin studies suggest that genetic factors contribute to continuity in mental health problems and environmental factors are the major contributor to developmental change. We investigated the influence of psychiatric risk alleles on early-onset mental health trajectories and whether these were subsequently modified by exposure to childhood victimization.

Method. The sample was a prospective UK population-based cohort, the Avon Longitudinal Study of Parents and Children. Developmental trajectories in childhood (approximately ages 4 to 8 years) and adolescence (approximately ages 12 to 17 years) were estimated for emotional problems. Psychiatric risk alleles were indexed by polygenic risk scores (PRS) for schizophrenia using genome-wide association study results from the Psychiatric Genomics Consortium. Chronic peer victimization in late childhood (ages 8.5 and 10.5 years) was assessed as an index of environmental exposure. Individuals with sufficient data on emotional problems, PRS and victimization were included in the main analyses: N=3988.

Results. Higher schizophrenia PRS were associated with a trajectory of early-onset increasing emotional problems (OR=1.18 (1.02-1.36)) compared to a trajectory of low-stable emotional problems. Subsequent exposure to victimization increased the likelihood of transitioning from a low-stable emotional problems trajectory during childhood (before exposure) to an increasing trajectory in adolescence (after exposure) (OR=2.59 (1.48-4.53)).

Conclusions. While the early development of emotional problems was associated with genetic risk (schizophrenia risk alleles), the subsequent course of emotional problems for those who might otherwise have remained on a more favorable trajectory was altered by exposure to peer victimization, which is a potentially modifiable environmental exposure.