One in ten new fathers might suffer from post-natal depression, even though most cases go undetected and untreated, according to U.S. researchers writing in the Journal of the American Medical Association. Still, the rate is lower than in new mothers, the BBC reports. In the study, based on a review of previous medical literature, they found that lack of sleep, new responsibilities, or supporting a spouse with post-natal depression could trigger it in men. New dads are generally happiest in the weeks following the baby’s birth, with depression appearing after three to six months, at which time from 10 to 25 per cent of men had post-natal depression, even though they had not had the hormonal surges of giving birth. Men are far more likely to suffer if their partner is also depressed, they report.