Hostile parenting can contribute to a child's sleeping problems. Mothers who shout or smack are more likely to have toddlers with sleep difficulties - but researchers do not know if the aggressive parenting style is a cause or effect of the problems.
A paediatrician from Melbourne's Royal Children's Hospital has analysed data from 4600 families to see if parenting methods had any impact on the sleep behaviour of children between the ages of one and three.
Harriet Hiscock found children were nearly twice as likely to have sleep problems that persisted through the toddler years if their mother's parenting style was "hostile" - characterised by yelling or physical punishment such as smacking - rather than "warm".
But her research has opened a chicken-and-egg debate because it is not clear whether the sleep problems are caused by the mothers' parenting, or if the frazzled mothers have resorted to shouting at their sleep-deprived, cranky children.
"It's always a cause-and-effect argument and you can't really conclude from this which one occurs first," Dr Hiscock said.
She found the biggest predictor of persistent sleep problems was a child's health.
Babies and toddlers who have chronic health problems such as asthma or autism were more than three times more likely to suffer sleep problems than healthy children.
The data from the Longitudinal Study of Australian Children found that 75 per cent of young children had no sleep issues.
Two-thirds of sleeping problems reported at age one were resolved by the second study, but about one in 20 had sleep problems that persisted over the years.
Mothers' parenting style was not a big factor in sleep problems at the age of one, but became an issue by the second study.