Men are as likely as women to suffer from postnatal depression, a study shows.
One in ten fathers - the same ratio as mothers - were found to suffer before or after birth.
By the time their child reaches 12 weeks, as many as one in four are feeling down.
The symptoms observed in the American study are not thought to be hormonal - as they are in women - and are instead probably a response to the pressures of fatherhood.
These include the expense of having children, changed relationships with partners and fear of paternal responsibility.
In the early weeks, the lack of sleep and extra domestic chores also take their toll, say mental health experts.
The study put the overall rate of depression among new fathers at 10.4 per cent - double the estimated 4.8 per cent for all men in any 12-month period.
Around 8 per cent were affected in the 12 weeks before and after birth, according to the Eastern Virginia Medical School research.
The team, led by James Paulson, reviewed 43 studies involving 28,000 people. They found parents were more likely to be down if their partner was too.
It is estimated around one in ten women suffers postnatal depression, even if they have never had mental health problems. Without treatment the condition can last for months.
Although most women have a few days of 'baby blues' shortly after birth, postnatal depression can kick in up to six months later.
Dr Paulson said paternal depression was serious because it can have 'substantial emotional, behavioural and developmental effects on children'.
The study was reported in the Journal of the American Medical Association.
