The report - The effect of income on New Zealand children's behaviour: The influence of maternal stress and children's screen use - used data from the Growing Up in New Zealand study, and found that higher levels of screen time - four hours or more per day - led to pre-school children playing up and that could not be explained by socio-economic differences.
Meanwhile, having lower incomes increased maternal stress and, in turn, that was also associated with more behavioural problems in children.
Dr Jaimie Monk, a fellow at Motu Research told Saturday Morning host Susie Ferguson the study focused on the role of income in children's behavioural, social and emotional development.
"When you're looking at families, you can't really separate out this role of income and stress - they were very related."
The researchers examined maternal stress during the child's first 1000 days.
"We found that ... periods when income was higher, stress was lower - which is probably reasonably logical to most people listening."
The biggest reasons for differences in children's development were related to housing and health, she said.
This depended on whether their mothers owned the home or were renting - and how often they were having to move, "which is obviously quite a stressful thing that happens if you're pregnant".
They looked deeper into the factors behind differences in behaviour issues between income groups.
"What's most important for children at this particular stage of their development is ... all to do with this parent-child relationship, so back and forth interactions between parents and children - these are often known as 'serve and return interactions' - and these are what build healthy brain development for pre-school children."
Central to this was mother-child relationships, she said.
"In particular, stress was a big part of it - and parenting related to stress. So things like being more likely to yell and argue with kids, but also differences in reading together and screen use."
"Screen use is a complicated thing... We do need to take ... stress into account when we're looking at it...
"At these lower levels - particularly if parents are parenting by themselves, without a lot of support and they're feeling stressed, and they feel like a small amount of screen use is giving them a break to cook dinner, or just to take some time out - I can't see that as being a particularly big issue.
"I would actually encourage parents... if your kid wants to watch Bluey for 30 minutes to give you a break, and you can feel better, and be more engaged in your parenting afterwards, then that's great.
"But it's at these higher levels [of screen time] that we're really seeing the problems - four, five, six, seven hours a day - and that seems to be crowding out some of the more healthy development."
Ferguson asked what was behind the rise in screen time.
It was not possible to isolate specific factors, as many were interrelated, Monk said.
"I think a lot of these families have a lot of things going on, and there are a lot of these ... structural issues happening for them.
"I'm always loath to say, 'You should not give [children] more than say two hours a day.' There's a lot going on in these families, often."
The first 1000 days - or the first three years of a child's life - were crucial, particularly in terms of interventions and support for families, because it was when their brains were developing.
"All their brain architecture is kind of coming together during that period."
So what was the link between income and behavioural development?
"What this work shows is that income is important, but listing incomes is a complicated business.
"If we can also take a lens to look at stress, and if we're developing social services that support families, we can actually think carefully about is this service helping decrease stress for families? And if it is, then that's going to have ongoing benefits for children, particularly for pre-school children."
