More than one in four youngsters in the UK are growing up in families facing multiple challenges such as parental depression and financial hardship, according to new research.
Some 28% of families faced two or more of 10 risk factors seen as harmful to children's development, the study from the Institute of Education, University of London, found.
Just over four in 10 children did not experience any of these risk factors in early childhood. A further three in 10 faced only one.
Previous research suggests that most children living with only one risk factor will not end up with a major developmental problem. It is multiple family difficulties that are most damaging.
The study's authors also discovered that Bangladeshi children were most likely to be exposed to multiple family difficulties. Almost half of them (48%) experienced two or more risk factors - financial hardship was often one of them - compared to only 20% of Indian children.
The 10 risk factors considered were living in overcrowded housing; having a teenage mother; having one or more parents with depression, or a physical disability, or low basic skills; substance misuse; excessive alcohol intake; living in a family experiencing financial stress, or worklessness or domestic violence.
The researchers did not find a dominant pattern of risks. For example, for families facing three risks, the most common combination was smoking during pregnancy, financial stress and teenage motherhood. However, this combination of factors applied to only 6% of families living with three risks.
The paper's authors, Dr Ricardo Sabates, of the University of Sussex, and Professor Shirley Dex, of the Institute of Education, said the great diversity of risk-factor combinations complicated matters for policy-makers.
"It seems that there is relatively little to be gained from policy interventions that tackle clusters of disadvantages rather than individual disadvantages," they said. "However, there may still be some knock-on effects from tackling some individual risk factors and disadvantages."
The initial findings of the study are reported in "Multiple risk factors in young children's development", a working paper published by the Centre for Longitudinal Studies, Institute of Education.