Previous studies have shown a negative correlation between effortful control (EC) and depressive symptoms. EC is defined as the efficiency of executive attention, which may
be reduced by the attentional impairment associated with depression. However, the mechanism underlying this correlation is still unclear. We investigated the relationship between EC and depressive symptoms with the hypothesis that cognitive motivation, or need for cognition (NfC), is a possible mediator of this relationship. Participants were 178 Japanese university students. Each completed the Zung Self-Rating Depression Scale, Effortful Control Scale, and Need for Cognition Scale at baseline and follow-up assessments. Supporting our hypothesis, mediation analyses revealed a significant indirect effect of depressive symptoms on EC that was mediated by NfC. In addition, our data demonstrated a direct effect of depressive symptoms on EC. Longitudinal analysis indicated that an increase in depression and a decrease in NfC occurred synchronously, while NfC predicted an increase in EC over time. Depressive symptoms may decrease executive functioning and effortful control both directly and indirectly, the latter effect being mediated by motivation. These findings imply that a motivational deficit may partially explain the decreased EC found in people suffering from depression.