Polygenic risk for schizophrenia predicting social trajectories in a general population sample

We investigated (a) whether polygenic risk for schizophrenia predicts different trajectories of social development among those who have not developed psychoses and (b) whether possible associations are PRS_SCZ-specific or evident also for any polygenic risk for mental disorders, e.g. for major depression.

Participants came from the population-based Young Finns Study (n = 2377). We calculated a polygenic risk score for schizophrenia (PRS_SCZ) and for major depression (PRS_DEP). Diagnoses of psychotic disorders were derived from the hospital care register. Social development from adolescence to middle age was measured by (a) perceived social support from friends, family, and a close other, (b) perceived sociability, and (c) family structure (partnership status, number of children, age of first-time parenthood).

Among those without manifest psychoses, high PRS_SCZ predicted lower experienced support from friends (B = -0.04, p = 0.009-0.035) and family (B = -0.04, p = 0.009-0.035) especially after early adulthood, and also lower perceived sociability (B = -0.05, p = 0.010-0.026). PRS_SCZ was not related to family structure. PRS_DEP did not predict any domain of social development.

Individuals at high PRS_SCZ (not converted to psychosis) seem to experience a lower preference to be with others over being alone. Individuals with high (v. low) PRS_SCZ seem to have a similar family structure in terms of partnership status or number of children but, nevertheless, they experience less support from their family. Among those not converted to psychosis in a typical age period, high PRS_SCZ may predict a 'later risk phase' and reduced functional resilience when approaching middle age.