Children whose parents split up are less likely to be sensitive and warm towards their own children in the next generation, researchers have found.
The researchers, who have been following 1265 children born in Christchurch 39 years ago, have found that children who experienced more parental separations in childhood show on average less parental sensitivity and warmth to their own children, are more "over-reactive" when their children misbehave, and use more physical punishment.
The effect is small. Parental separation explains only between 2 and 12 per cent of the variance in parenting outcomes in the next generation.
But lead author Dr Myron Friesen of Canterbury University said separation was often associated with other things such as violence and child sexual abuse which all affected future generations.
"Not only do you have the breakdown in the marital relationship, but there can be all kinds of things going on around that," he said.
"With the relationship breakdown, you are going to have children not living with one of their parents for possibly quite some time, so you are going to have all that readjustment.
"Typically it takes a couple of years, and most children survive quite well. But there is a concerning minority that don't, and that minority goes on to experience problems later in life."
The researchers have broken new ground by using the long 39-year history of the Christchurch study to look at whether the effects of separation increased for children who experienced more than one parental separation.
Looking just at the 337 people from the original group born in 1977 who were living with their own or a partner's children at age 30, they found that 24 per cent had experienced one parental separation in their own childhood, 9 per cent had seen two separations and 4 per cent had seen three or more parental breakups.
"Every time that happens it is a new traumatic event that child needs to adjust to," Friesen said.
"Every time there is a new change in that parental relationship, children are forced to go through a whole series of adjustments in relationships with their parents, in family structure, and in the boundaries and rules that they have, and that's a challenge."
Those who lived through more parental breakups were significantly less likely to be sensitive to their own children's verbal and non-verbal signals, and were less "warm" to their children - a measure based on showing affection and enjoying doing things with them.
They were also significantly more likely to use physical punishment.
However, this wasn't just because of the parental separation. Those who lived through separations were also more likely to have seen conflict or violence between their parents - 37 per cent of those who saw two or more separations, and 40 per cent of those who saw just one separation, but only 20 per cent of those whose parents stayed together.
They were also more likely to have suffered childhood sexual abuse - 27 per cent of those who saw two or more parental separations compared with 16 per cent of those whose parents stayed together, although in this case those who experienced only one separation suffered even less sexual abuse (12 per cent).