Investigating functional impairment as a mediator of the association between internalising symptoms and low wellbeing

There is a lack of focal research on transdiagnostic factors that explain the influence of internalising symptoms on wellbeing. It is plausible that low wellbeing may be a consequence of functional impairment resulting from symptoms, but this has yet to be explored. Internalising symptoms (i.e., major depression, persistent depression, generalised anxiety), impairment, and wellbeing were assessed in a community sample ( N = 408) using semi-structured clinical interviews and self-report measures. Structural equation models were conducted to analyse effects of symptoms on overall wellbeing (concurrently and with wellbeing assessed one month later), mediated by impairment. Exploratory analyses examined the mediating effect of impairment on the relationship of individual depression and anxiety symptoms with wellbeing. Impairment accounted for a portion of the association between interviewer-rated major depression and generalised anxiety symptoms and wellbeing, but not persistent depression symptoms. The results for anxiety were replicated with self-report measures, but not for major depression. Indirect effects generally persisted over time, but only when not controlling for baseline wellbeing. Exploratory analyses revealed significant indirect effects of individual symptoms of generalised anxiety (uncontrollability, restlessness, irritability, sleep disturbance, fatigue, and troubles concentrating due to worry) and major depression (depressed mood, anhedonia, troubles concentrating, feelings of guilt/blame, and fatigue). These findings support the hypothesis that impairment associated with internalising symptoms is one factor connecting symptoms, particularly anxiety, to reduced wellbeing, and thus is an important research area and therapeutic target. • The detrimental effect that generalised anxiety symptoms have on wellbeing is consistently partially explained by the effects symptoms have on functioning in important life domains. • Impaired functioning also accounts for a proportion of the relationship between depressive symptoms and wellbeing, but this finding is less consistent • Impaired functioning partially accounts for why elevated symptoms lead to poor wellbeing cross-sectionally and over one month. • Individual symptoms play important roles in driving functional impairment and reduced wellbeing, particularly uncontrollability, restlessness, irritability, sleep disturbance, fatigue, and troubles concentrating in generalised anxiety. In major depression, depressed mood, anhedonia, troubles concentrating, feelings of guilt/blame, and fatigue are important.