Why are stepfathers detrimental to child development? Exploring the effects of stepfathers on child outcomes in the UK.

Whilst stepfather presence has consistently been associated with detrimental effects on child development, studies rarely explore whether these effects are related to confounding changes in the investments children receive. Using ALSPAC, we explore stepfather effects on children’s height, educational achievement and behavioural difficulties at age 7 whilst controlling for measures of direct investments. We fail to find any stepfather effects on height. However, stepfather presence is associated with a reduction in children’s educational achievement and an increase in children’s behavioural difficulties. For educational achievement, this negative effect of stepfather presence is reduced to non-significant levels when mother and partner’s investment levels are accounted for. For behavioural difficulties, this negative effect is also reduced though significance is retained. Furthermore, specifically for behavioural difficulties, we find that investment from stepfathers do not have any beneficial effects. Our results suggest that, for educational achievement, stepfather effects are due to lower levels of investment levels children receive. For behavioural difficulty, stepfather effects are due to multiple factors whereby presence itself is detrimental, investment levels are reduced, and investment from stepfathers are ineffective.