Examining which factors influence age of onset in males and females with schizophrenia

Objective: Data from the 2010 Australian National Survey of High Impact Psychosis (SHIP) was used to examine (1) what variables influence age of onset (AOO) for males and females, and (2) whether influencing variables were different between the sexes. Method: Data from 622 schizophrenia patients in the SHIP sample was used. These included early life factors, encompassing family psychiatric history, childhood development, trauma and parental loss. Factors occurring within 12 months of diagnosis were also used, including drug/alcohol abuse and premorbid work and social adjustment. Based on the recognised differences in symptom profiles and AOO between the sexes, these factors were regressed separately for males and females. Results: Stepwise linear regressions showed that a family history of psychiatric disorders was significantly associated with earlier AOO in both sexes. Other variables differed between males and females. Specifically, for females, an earlier AOO was associated with poor premorbid social adjustment and the loss of a family member in childhood. Older AOO was associated with immigrant status. For males, a younger AOO was associated with unemployment at onset, poor premorbid work adjustment, parental divorce in childhood, and lifetime cannabis use. A higher premorbid IQ was associated with an older AOO. Conclusion: Familial predisposition to psychiatric illness is related to earlier AOO of schizophrenia independent of sex. Males appear to have more individual-based predictive factors while females seem to have more community/social-based influences. Future directions for research in schizophrenia are suggested.