Babies with depressed dads are at risk of developing behavioural and social problems by the time they start school, researchers have found.
The finding has sparked calls for doctors to check new dads for signs of depression in a similar way to how mums are routinely screened for postnatal depression.
The Australian researchers found the effects of paternal depression in the first year of a baby's life were just as detrimental to a child's development as postnatal depression.
Babies with depressed dads were more than three times as likely to have behavioural, emotional and social problems by the time they were five as infants whose dads didn't suffer depression.
Even after stripping out the effects of the mother having postnatal depression, the family's socio-economic status and education levels, the risk of the child having problems remained high.
Lead researcher Dr Richard Fletcher, of Newcastle University's Family Action Centre, said the findings suggested GPs and other healthcare workers should check dads for paternal depression so they could get help quickly.
"What we have is a system that says to mum, 'are you depressed?', and if the answer is yes then she is steered towards support," he said.
"But at no time does anyone say, 'is your partner depressed?'
"Generally, dads respond to treatment in a similar way to mums, but dads are less likely to get treatment."
Postnatal depression is estimated to affect about one in seven Australian mums. The number of dads with paternal depression is believed to be about half that rate.
In their study of 2600 families, Dr Fletcher and his colleagues found 1.3 per cent of dads had paternal depression while 2.6 mums reported postnatal depression.
The effects of parental depression were different for boys and girls.
Depression in dads was more likely to lead to more hyperactivity and social problems in boys than girls, who had larger struggles with emotional and conduct issues.
Mums with postnatal depression were found to have a bigger effect on boys' social skills and girls' conduct.
Dr Fletcher said reasons why dads with depression impacted the development of their children were sketchy.
He said dads were often an "anchor for discipline" in the family and if they were depressed they were less likely to set boundaries, possibly opening the way for boys to become hyperactive.
Other studies had shown when dads were depressed they were less likely to read and play with their children, activities which can help teach youngsters about behaviour.
The study was published by The Medical Journal of Australia.