The findings could improve drug treatment for depression by tailoring the amount of drug to high-risk periods for suicide. Heart rate, temperature and secretion of steroids, hormones and brain chemicals change through the day. In people with depression and anxiety, there are variations from the norm which may trigger a suicide attempt.
Scientists from the Ferrara Medical School studied 212 patients admitted to hospital after self-poisoning attempts. They found a significant daily rhythm. For the general population the peak time was 5.45pm; for men 6.37pm and for women, 5.16pm.
Previous studies have shown that the risk of suicide is greatest in the early morning and early afternoon. Writing in tomorrow's British Medical Journal, the scientists say: 'As suicide and attempted suicide have different psychological causes and epidemiological risk factors, these data support the hypothesis that chronobiologically determined changes influence suicidal behaviour.'
Increased activity of the adrenal glands in early afternoon, and a decrease in the production of serotonin, a mood-influencing brain chemical, were important factors.