Depression may lead to neglect of the child or inappropriately forceful behaviours.
Post natal depression among new fathers is a common phenomenon, according to a study which shows that becoming a parent can be emotionally challenging for many men.
There is also a major risk that the condition remains undetected using today's screening instruments, and that fathers do not receive the help they need.
The study of 447 new fathers showed that the established method of detecting depression EPDS (Edinburgh Postnatal Depression Scale) works poorly on men.
"Current statistics may not tell the whole truth when it comes to depression in new fathers," said Elia Psouni, from Lund University in Sweden.
"The screening method does not capture symptoms which are particularly common in men, such as irritation, restlessness, low stress tolerance, and lack of self-control," said Psouni.
Although one-third of the depressed fathers in the study had thoughts of hurting themselves, very few were in contact with the health care system.
Among those who were classified being moderately to severely depressed, 83 per cent had not shared their suffering with anyone.
"Telling people you feel depressed is a taboo and as a new parent, you are expected to be happy," said Psouni.
"On top of that, previous research has shown that men are often reluctant to seeking help for mental health issues, especially depression," she said.
"Among dads, depression is common even at the end of the first year, which may be due to the fact that they rarely get help, but there may be other explanations," said Psouni.
"Whatever the reason, it is important to monitor dads' well-being as their part of the parental leave usually occurs towards the end of the child's first year of life," Psouni added.
Detecting depression in new parents is crucial - not only for their own sake but also because depressed parents often become less perceptive to the needs of their child, particularly if the child cries a lot.
Babies of depressed parents tend to receive less stimulation which, eventually, could lead to slower development.
In some cases, depression may lead to neglect of the child or inappropriately forceful behaviours.