Unhappy parents should not stay together "for the sake of the children", as divorcing is less harmful if it takes place earlier in childhood, new research shows.
The first large study to assess the emotional impact on children of their parents splitting up has found that the greatest risk of repercussions in the form of bad behaviour and disobedience come in late childhood and early adolescence.
The analysis of 6000 children born in the UK at the turn of the century found that those whose parents split up when they were between the ages of 7 and 14 were significantly more likely to suffer emotional and behavioural problems than those whose parents stay together.
However, there was no discernible difference between children aged between 3 and 7 whose parents divorced and those who did not.
The University College London scientists behind the new research believe divorce is more damaging to adolescents than to younger children, because they are more socially sensitive and better able to pick up on negative relationship dynamics.
The team examined reports of children's mental health at 3, 5, 7, 11 and 14, including emotional problems such as feelings of low mood and anxiety, and behavioural issues such as disobedience.
They compared information on children who experienced a family split with those who did not. A fifth of children in the study saw their parents separate between the ages of 3 and 14.
Among older children, increased emotional problems were noticed for both boys and girls, but more severe behavioural issues were seen only in boys.
The study also suggested that, after a family break-up, children from more privileged backgrounds were just as likely to have mental health problems.
Professor Emla Fitzsimons, who co-authored the study, said: "With adolescent mental ill health a major concern nationally, there's a pressing need to understand the causes."
She added that older children are also more likely to be affected because disruption to schooling and friendships is often greater.
Published in Social Science & Medicine, the study also investigated the impact of a break-up on mothers' mental health and financial resources.
Across the UK, women accounted for 90 per cent of lone parents, and most children in the study lived with their mothers after a split.
Mothers reported, on average, more mental health problems than those still with their partners if they separated when their children were older.
This is believed to be because the financial impact of divorce was greater the later on in the marriage.
According to the Office For National Statistics, there were 101,669 divorces of heterosexual couples in 2017.
Just over four in 10 marriages in the UK end in divorce.
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