Intolerance of uncertainty, psychopathology, and emerging adult sibling relationships

Intolerance of uncertainty is often associated with emerging adult psychopathology, including depression, anxiety, and substance use behaviors. However, positive sibling relationships, which are known to support emerging adult mental health during stressful periods, may mitigate the stress related to uncertainty. Thus, this study investigated the role that sibling relationships may have between uncertainty and psychopathology. In a two-cohort longitudinal sample of emerging adults (N = 189, Mage = 20.89), the moderating role of positive sibling relationship quality was examined between intolerance of uncertainty and later depression, anxiety, and substance use. Intolerance of uncertainty only predicted anxiety, while positive sibling relationship quality moderated the association between intolerance of uncertainty and later substance use, with low levels of sibling relationship quality showing a protective effect on substance use. Subsequent analyses revealed positive sibling relationship quality significantly moderated the association for marijuana only when the autoregressive effect was removed, resulting in greater marijuana use when sibling relationship quality was high. Positive sibling relationship quality also moderated the effect on health risk substance use, resulting in less substance use when sibling relationship quality was low. Findings underline the role that sibling relationships can play as both risk and resiliency factors for distinct emerging adult substance use behaviors. Sibling relationships continue to serve as significant sources of influence on emerging adult psychopathology.