<p>Adverse life events have been associated with increased mental illbeing and decreased wellbeing. These associations may partly reflect reverse causality and confounding genetics. Few studies have accounted for such effects, and few have compared the effect of adversities within and across different mental health outcomes. Our sample includes 1987 monozygotic and dizygotic twins born 1945-60, in the Norwegian Twin Registry, who responded to two questionnaires six years apart. We used biometric modelling to estimate genetic overlap and linear mixed models to control for previous levels of illbeing and wellbeing as well as genetic confounding in the associations between adverse life events and these outcomes. Our results indicate causal effects of cumulative adversity on increased illbeing and decreased wellbeing. Of the six adversities examined separately, financial strain and conflicts in romantic relationships showed the most profound effect on both outcomes. Conflicts with family/friends/neighbours and problems at work seem to primarily increase illbeing, while serious illness or injury mainly decrease wellbeing. This study supports previous findings that cumulative adversity represents a risk for increased illbeing and decreased wellbeing. Hence, exploring the number of recent adverse events could give valuable insight into individuals’ stressor load, and the reduction and prevention of such events should be important targets for preventive programs and policy. Importantly, our findings further suggest that the events that increase illbeing are not always overlapping with those that decrease wellbeing. This should be taken into consideration when assessing the needs of individuals after difficult experiences.</p>