It's not just women - as many as 10 per cent of new fathers are hit by crippling depression that can last for several months, a long-term study of Australian families from 2004 to 2010 has found.
The study, by researchers from the national Parenting Research Centre and the Murdoch Children's Research Institute analysed data collected from 3471 biological fathers taking part in the Growing Up in Australia: A Longitudinal Study of Australian Children.
They had mental health assessments when their children were aged three to 12 months, two to three years, and four to five years old.
Results showed that 9.7 per cent of fathers suffered postnatal depression in the first year of their child's life, compared with 9.4 per cent for mothers - showing that men were just as likely as women to succumb to anxiety and depression following the birth of their children.
Younger fathers were particularly vulnerable, with those aged under 30 facing a 40 per cent increased likelihood of developing depression. Those who lived in more disadvantaged communities were also more likely to report psychological distress, the report found.
But the figures do not reflect the full extent of the problem, experts say, with under-reporting of male postnatal depression masking the true numbers, which could be close to double those reported, according to the Post and Antenatal Depression Association.
PANDA reported that more than 29,000 Australian men were affected - enough to fill 68 jumbo jets - but the stigma attached to all forms of mental illness meant the condition was going undiagnosed and under-reported in thousands more.
PANDA chief executive officer Belinda Horton said often fathers suffered in silence, either not fully recognising the symptoms, or not feeling comfortable enough to come forward.
"Many of the fathers who are suffering feel they should be the stronger parent and are afraid of being judged as a bad parent," Ms Horton said. "Finding the words to express how bad you are feeling can be incredibly difficult and then finding someone to listen without judgment is also hard."
Ms Horton said families, friends and communities should keep an eye on all new parents and remember to check on how men were coping. She said many of the medical system's education campaigns and support programs were aimed at women, with very little information and advice given to fathers.
"There is a message there in the figures - dads are 50 per cent of the equation in all things and we need to pay much more attention to their wellbeing."
Fathers who felt they might be experiencing the symptoms of postnatal depression should find a friend or colleague to confide in, contact a helpline or their GP.
"Sometimes getting help from someone removed from the close circle of family and friends can make talking easier," Ms Horton said.
"Men should be talking about how they feel, even where there is not a diagnosis of postnatal depression - there are so many steps in the process before a diagnosis is possible, but just talking with others who understand is very important."
Fathers who were experiencing worrying emotions and thoughts for longer than two weeks and who were feeling constantly anxious should get help as soon as possible, she said.
"That two-week mark is very important because it's in the literature for diagnosing depression," Ms Horton said.
"It's much more than feeling a little fatigued and disoriented because your world has been turned on its head; it's a very low mood and high levels of anxiety. If dad is feeling on edge and unable to slow his thinking, not able to trust his decisions or is losing focus, then it's time to act."
If left untreated, the symptoms could get significantly worse. Depending on the severity, it could negatively affect nearly every area of a person's life, including their relationships, their ability to work and care for themselves and others.
In the most severe cases, untreated postnatal depression could pose a threat to the life of a parent or child.
Jan Nicholson, study co-author and director of research at the Parenting Research Centre, said the birth of a baby brought enormous changes into both parents' lives.
"Fatherhood is a great time of excitement and significance," Professor Nicholson said.
"However, even for fathers with other children, a new baby results in sleep disruption combined with increased financial demands, domestic burdens, and the need to renegotiate the balance between work, parenting, family roles and responsibilities. It is not surprising then that fathers, like mothers, can find this a challenging time."
She said distress in the early years appeared to put fathers at further psychological risk when children became toddlers and pre-schoolers.
By the time children were four to five years of age, 30 to 60 per cent of those who had previously reported distress, again reported distress at this time, compared with just five per cent of fathers who had not previously reported any distress.
Lead researcher Rebecca Giallo said the study highlighted the need for early-intervention programs and support networks for men in tackling the illness.
WHERE TO GET HELP
PANDA Perinatal Helpline: 1300 726 306, panda.org.au
Mensline: 1300 789 978, mensline.org.au
Lifeline WA: 13 11 14, lifelinewa.org.au
Beyond Blue Info Line: 1300 22 46 36, beyondblue.org.au