May 2, 2006
Suicide risk linked to month of birth: study
LONDON -- People born in spring or early summer in the northern hemisphere have a 17 percent increased risk of committing suicide than those with birthdays in the autumn or early winter, researchers said on Tuesday.
They found that women born in April, May and June were 29.6 percent more likely to take their own lives while men had a 13.7 increased risk.
"Our results support the hypotheses that there is a seasonal effect in the monthly birth rates of people who kill themselves and that there is a disproportionate excess of such people born between late spring and midsummer compared with the other months," Dr Emad Salib, of Liverpool University, northwest England, said in a report in the British Journal of Cancer.
Salib and Mario Cortina-Borja, of University College London, analyzed data on 26,915 suicides and deaths from undetermined injuries in England and Wales between 1979 and 2001. All of the people involved had been born between 1955 and 1966.
They said seasonal birth trends for illnesses including breast and testicular cancer, coronary heart disease, brain tumors, Crohn's disease and early onset non-Hodgkin's lymphoma had been established.
Their findings are in line with reported higher birth rates in the spring and early summer of people suffering from alcoholism and mood disorders whose suicide deaths are about 10 percent of the annual total in England and Wales.
But Salib said the findings are not consistent with research showing schizophrenia, which is also linked to suicide risk, is associated with winter births.
The researchers suggest exposure of the fetus to factors such as maternal diet, infections, toxins, the amount of sunlight and hormones could trigger physical and psychiatric disorders, including suicide, in adulthood.
Salib hopes the findings will improve understanding about suicide and the ability to predict people more at risk.