This paper finds that children who spend 12 months at home with their mother after being born become adults who are more satisfied with life than those who spend just 5 months at home or in childcare.
The study analyses the effects of reforms in the former German Democratic Republic where, in 1976, mothers with at least 2 children were granted 52 weeks compared with 26 weeks parental leave, a policy that was extended to all parents regardless of the number of children in 1986.
The researchers use household survey data to look at the life satisfaction levels as adults of people born and raised in East Germany between 1980 and 1989.
When compared with adults who had spent just 5 months with their mother and 7 months in a childcare centre, participants who had spent a year at home with their mother were on average 8% more satisfied with their life. (e.g. just looking for a way to express this simply)
Some of the difference was explained by personality development and this was particularly the case for poorer children and boys. The researchers point out that better health could also explain increased levels of happiness among those from a better off back-ground.
Despite this, the researchers emphasise that all individuals in the study seemed to benefit in terms of life satisfaction from the reforms and conclude that spending more time with the mother in the first year of life matters for individuals in the long run.