This study examines how relationship transitions affect subjective well-being (SWB) and how this effect changes over time. We used prospective data containing information about 18 years of young adults’ lives (PSIN,N = 5,514). SWB was measured with the Satisfaction with Life Scale.Within-person multilevel regression analyses showed that dating, unmarried cohabitation, and marriage had additional well-being enhancing
effects. After entry into a union, well-being slowly decreased. A large SWB decrease was
found after union dissolution, but through adaptation or repartnering well-being increased
again. Well-being of never-married and never cohabiting young adults decreased slowly
over time. These effects were independent of parenthood and employment. Our results
confirm expectations from the resources theory but contradict some assumptions of the set-point theory.
Key words: adjustment; cohabitation; dating; fixed effects; models; union formation; well-being