BACKGROUND Schizoid personality and poor social adjustment have been thought of as common antecedents of schizophrenia but the existing literature is inconclusive. We have carried out a large cohort study with improved methodology.
METHOD The premorbid personality and adjustment of 50,054 Swedish men were assessed on entry into the army at the age of 18. Individuals who developed schizophrenia or another psychosis after 15-year follow-up were identified. Odds ratios for variables independently associated with the later development of schizophrenia were calculated, adjusting for potential confounders.
RESULTS Four variables reflecting early problems with interpersonal relationships were strongly associated with later schizophrenia and, to a lesser extent, non-schizophrenic psychoses, but also occurred commonly in the cohort as a whole. These associations with schizophrenia persisted after early-onset cases were excluded, though their predictive value was low (3.0%, 95% CI 1.5-4.5).
CONCLUSIONS Some aspects of premorbid personality and adjustment may act as risk factors for schizophrenia. The results appear to be most consistent with a multi-factorial aetiology for schizophrenia and offer tentative support for a psychological disturbance mediating genetic and environmental effects on the causal pathway to the illness.