The seasonal risk for deliberate self-harm. Determined by place of birth, but occurrence determined by place of residence.

Groups at seasonal risk for deliberate self-harm (DSH) vary according to their geographic location. It is unknown, however, if seasonal risk factors for DSH are associated with place of birth or place of residence as these are confounded in all studies to date. In order to disaggregate place of birth from place of residence we examined general and seasonal risk factors for DSH in three different population birth groups living in Western Australia: Australian Aborigines, Australian born non-Aborigines, and UK migrants. We found Aborigines are at much higher general risk for DSH than non-Aborigines, but are not at seasonal risk, whereas non-Aboriginal Australians and UK migrants are. For UK migrants, this is only found for females. For all groups at seasonal risk this peaks during the austral (southern hemisphere) spring/summer. Furthermore, non-Aboriginal Australians and UK migrants show a consistent pattern of increased case fatality with increasing age. In contrast, case fatality does not increase with age among Australian Aborigines. Overall, despite living in the same environment, the three birth groups show different patterns of seasonal risk for DSH. In particular, the sex difference found between UK migrants and non-Aboriginal Australian birth groups suggests that predisposition toward seasonal risk for DSH is established early in life, but when present this is expressed according to local conditions.