A study from the University of Otago in Wellington, published in the international Journal of Epidemiology and Community Health, examined the experiences of more than 6500 first-time parents in New Zealand in 2004-2005 and 2008-2009.
As well as the birth of the first child improving mental health, the study claimed it could also reduce psychological distress.
Authors Sarah McKenzie and Kristie Carter said the results were good news for Kiwi parents.
"It shows the effect of becoming a parent for the first time tends to have a positive effect on parents' mental health," Ms McKenzie said.
"Whereas no real impact on mental health was found for parents having subsequent [second, third or fourth] children."
The improvements in mental health were positive, but not large, she said.
First-time mum Amy Fanning has learned not to sweat the small stuff after giving birth to Lauren four months ago.
The 29-year-old suffered bad morning sickness and shingles during pregnancy, and her daughter was temporarily deprived of oxygen after labour, but had been a happy and contented baby since.
"As long as she's breathing, [and] we can provide for her, everything's pretty good."
The former internal auditor said she used to find her work stressful but becoming a mother changed her perspective and priorities.
"Some people say, ‘You come home from the hospital and where's the manual?', but it wasn't like that for me. I felt like she's my baby and I'm going to nurture and protect her."
She and husband Matt, a property adviser, went to a single income when Lauren was born. Mrs Fanning said they were lucky they could get by, and had a good support system of family and friends.
Family Centre social policy researcher Charles Waldegrave said the research showed that, despite the impact of sleeplessness and worries, first-time parents were resilient.
"Being a parent does affect people's sense of wellbeing overall. Being a parent is being involved in a major, generative process which is very fulfilling."
The researchers said their study tested a larger sample of people than other studies in the field, as it included men and women, and married, single, and co-habiting parents.
Dr Carter said more work was needed to look at the mental health of parents as their children got older, because of the strain on their income.
The study was funded by the Health Research Council.
- The Dominion Post
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