Schizoid-like features and season of birth in a nonpatient sample

People with the deficit subtype of schizophrenia differs from others with schizophrenia with regard to risk factors, signs and symptoms, biological correlates, treatment response, and course of illness. The deficit group, which is characterized by decreased social interests and a lack of depression, has a well-replicated association with June/July birth, which contrasts with the association of schizophrenia as a whole with winter birth. As some of the correlates of schizophrenia are found in subclinical form in the schizophrenia spectrum, we hypothesized that June/July birth would be associated with the combination of decreased sociality in the absence of depression in a nonpatient group as well.

The Beck Depression Inventory and Chapman's Perceptual Aberration, Magical Ideation, and Social Anhedonia scales were administered to university students. The Perceptual Aberration and Magical Ideation scale scores were combined into a single psychotic-like symptom score (PerMag). Blind to month of birth, each subject (N=425) was given a score that quantified the combination of social anhedonia and an absence of depression. Analyses were then performed in subjects in the upper 50% of PerMag scores who had complete data (N=171, 27.5% male).

June/July birth (p=.037) and male gender (p=.002) were both found to be associated with higher scores on the combination of social anhedonia and a low depression score; the interaction of these factors was not significant.

These results suggest that the same seasonal factor that contributes to the risk of deficit schizophrenia may affect brain development and personality characteristics in the general population.