Psychological Medicine

Brief Communication

Seasonality of suicide in Singapore: data from the equator

G.  PARKER  a1 c1, F.  GAO  a1 and D.  MACHIN  a1
a1 School of Psychiatry, University of New South Wales, Sydney, NSW, Australia; and Institute of Mental Health, National Cancer Centre and NMRC Clinical Trials and Epidemiology Research Unit, Singapore


Background. Studies in the northern and southern hemispheres consistently identify seasonal patterns in suicidal deaths. In many such studies, bimodal yearly peaks have been described for females as against unimodal ones for males. The current study examines the monthly variation in suicidal deaths in Singapore to determine if any seasonal patterns exist in an equatorial region.

Methods. Monthly suicidal death data over the decade 1989–98 were examined for the whole sample and for gender- and age-specific subgroups. Both von Mises' distribution and harmonic analysis techniques were used to interpret the data.

Results. Among the 2013 male and 1382 female suicides, there was minimal variation in patterning of suicidal deaths. We found a weak suggestion of a later peak for the females in mid-May as opposed to mid-February for the males, and the peaks for those less than 25 years of age were 5–6 months later than for the older age groups. The magnitude of all peaks was, however, very small suggesting chance variation. The harmonic analyses confirmed that patterning was ‘randomly' rather than ‘seasonally' determined.

Conclusion. In an equatorial region, there was no evidence of any ‘seasonal' patterning of suicidal deaths.

c1 Address for correspondence: Professor Gordon Parker, Mood Disorders Unit, Psychiatry Unit, Prince of Wales Hospital, Randwick, NSW 2031, Australia.