Mental disorders in young adulthood are common and often co-morbid, and they may be particularly harmful for education and employment in this age group.

There are marked sex differences and several diagnosis-related patterns in the associations between reported childhood experiences and environmental circumstances and adulthood mental disorders. The impact of adversities is probably composed of a wide range of factors from direct causal associations to complex, interacting environmental effects. Variations in the reported associations reflect the differing genetic and environmental transmission mechanisms of mental disorders.

Childhood living conditions and adversities are strongly associated with poor SRH and psychological distress in early adulthood. Early recognition of childhood adversities followed by relevant support measures may play an important role in preventing health problems in adulthood.

When considering actions to promote LTPA, there is not one single solution, because the perceived barriers vary by population subgroups.

Childhood living conditions are strong determinants of daily smoking. Much of their influence seems to be mediated through current living conditions, which are also determined by childhood conditions. Determinants of smoking behaviour are developed throughout the life course. The findings stress the importance of the respondent's education and parental smoking as determinants of smoking behaviour. Our results support the notion that intervention on smoking initiation and cessation should be considered throughout the life course. Parental involvement in fostering non-smoking would be important.