Background Social support is associated with better health. However, only a limited number of studies have examined the association of social support with health from the adult life course perspective and whether this association is bidirectional.

Methods Participants (n=6797; 30% women; age range from 40 to 77 years) who were followed from 1989 (phase 2) to 2006 (phase 8) were selected from the ongoing Whitehall II Study. Structural and functional social support was measured at follow-up phases 2, 5 and 7. Mental and physical health was measured at five consecutive follow-up phases (3–8).

Results Social support predicted better mental health, and certain functional aspects of social support, such as higher practical support and higher levels of negative aspects in social relationships, predicted poorer physical health. The association between negative aspects of close relationships and physical health was found to strengthen over the adult life course. In women, the association between marital status and mental health weakened until the age of approximately 60 years. Better mental and physical health was associated with higher future social support.

Conclusions The strength of the association between social support and health may vary over the adult life course. The association with health seems to be bidirectional.