Season of birth, age and negative symptoms in a Xhosa schizophrenia sample from the Southern Hemisphere.
OBJECTIVE
Seasonality of birth, more specifically winter/spring births, has been implicated as a risk factor for the development of schizophrenia. The primary aim of this study was to determine whether schizophrenia patients of Xhosa ethnicity born in autumn/winter have different symptom profiles to those born in spring/summer. The secondary aim was to determine whether the autumn/winter and spring/summer birth rates for schizophrenia patients of Xhosa ethnicity were similar to that of the general Xhosa population.


METHODS
Individuals with a diagnosis of schizophrenia, born in the Western and Eastern Cape Provinces of South Africa (n = 386), were categorized as autumn/winter-born (March to August) patients or summer/spring-born (September to February) patients. Negative global scores of the schedules for the assessment of negative symptoms were categorized as normal (rating of 0 and 1) or positive (rating of 2 to 5).


RESULTS
Patients born in autumn/winter were more likely to have avolition/apathy than those born in summer/spring. The results also showed that the age of the patients played a significant role in modifying the effect of the season of birth on symptoms of schizophrenia. Especially older people (more than 30 years old) born in autumn/winter had a higher incidence of avolition/apathy than those born in summer/spring (p = 0.026). Furthermore, in the relationship of birth season and avolition/apathy, the marital status of the patient was a significant independent explanatory variable, while gender was not. The study also showed a spring excess of 4% in birth rate compared with the general Xhosa population.


CONCLUSIONS
The results from our study support the existence of a seasonal birth pattern in an African schizophrenia population and suggest that avolition/apathy may underpin this seasonal pattern.
Jordaan
Esmè
E
MRC Biostatistics Unit, Bellville 7500, South Africa. esme.djhn@sun.ac.za
Niehaus
Dana J H
DJ
Koen
Liezl
L
Seller
Cathlene
C
Mbanga
Irene
I
Emsley
Robin A
RA
D000328:Adult; D000367:Age Factors; D044383:Black People / Q000523:psychology*; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology*; D005260:Female; D006801:Humans; D008297:Male; D017533:Marital Status; D009042:Motivation; D012307:Risk Factors; D012559:Schizophrenia / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology*; D012621:Seasons; D012737:Sex Factors; D013019:South Africa