Mediating effect of environmental rewards on the relation between goal-directed behaviour and anhedonia

Depression can be explained by certain behavioural patterns, especially low levels of environmental rewards; it is generally accompanied by infrequent goal-directed behaviour, increased depressed mood, and anhedonia. However, no research has statistically examined the mediating effect of environmental rewards on the relation between goal-directed behaviour and the symptoms of depressed mood or anhedonia. This study sought to determine whether such a mediating effect of environmental rewards is present in cross-sectional study. The participants included 101 patients diagnosed with major depressive disorders. Data were collected through three questionnaires measuring depression and behavioural patterns that maintain depression: the Center for Epidemiologic Studies Depression Scale (CES-D), the Environmental Reward Observation Scale (EROS), and the Behavioral Activation for Depression Scale-Short Form (BADS-SF). Mediation analysis was conducted using depressed mood and anhedonia as dependent variables, environmental rewards as the mediating variable, and goal-directed behaviour as the independent variable. Environmental rewards significantly mediated the relationship between goal-directed behaviour and anhedonia but not that between goal-directed behaviour and depressed mood. No significant relationships were found among depressed mood, goal-directed behaviour and environmental rewards. From these results, we conclude that low levels of environmental rewards accompanied by infrequent goal-directed behaviour can lead to increased anhedonia but not depressed mood.