"You just feel low and you stop liking the things you like," says 26-year-old Ben, one of thousands of men who has suffered from postnatal depression.
A New Zealand study suggests one in 25 are affected following the birth of a child.
More than 3,500 men took part in research by the University of Auckland in New Zealand.
We spoke to two new dads in Britain, James and Ben, about their experiences.
Ben Winterbottom tells Newsbeat that for him it began soon after the birth of his daughter Phoebe.
"I wouldn't say it ruined my life but it changed it massively for a few months," he explains.
"My wife was also going through the same thing at the same time so it was hard."
He tells Newsbeat he realised something was wrong when he felt a change in his natural character.
"You just feel low and you stop liking the things you like.
"I didn't want to go to work, I didn't want to play sport or even just go out and have a drink with friends."
But Ben realised he needed to get help after he snapped at his wife during a family meal.
"I told my wife I thought I had postnatal depression. We went to see a doctor and as soon as you've spoken someone things start to look up.
Unlike Ben, 29-year-old James Henry didn't realise that he was suffering with depression until it was over.
"I did have suicidal thoughts at my worst," he tells Newsbeat.
"It nearly broke my marriage and it would've done if my wife wasn't so strong."
James advises other new dads not to shrug off sudden changes in the way they feel.
"I turned to alcohol to cope and I'm not usually a drinker.
"I would also get wound up about things it wasn't worth getting wound up about," he said.
Postnatal depression affected both dads in different ways but they have similar advice for others.
Support of their friends and family helped them cope.
"I had a couple of moments when people said it was all in my head but that doesn't help, you want positive reactions instead of people saying that it'll soon be gone," Ben says.
"It takes time - just stick with it and go to see a doctor as soon as you can, a weight will be lifted off your shoulders as soon as you talk to someone."
And although James didn't go and see a doctor, he urges others to do so.
"My message to everyone else is simple - don't suffer like I did, seek medical advice and tell someone.
"I hope that because I've spoken out people will realise that it isn't only women that suffer from postnatal depression."
There's support and help on depression via these BBC Advice pages.