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

Background: 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.

Methods: 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).

Results: 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.

Conclusions: 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.