Positively biased appraisals in everyday life: When do they benefit mental health and when do they harm it?

To promote optimal mental health, is it best to evaluate negative experiences accurately or in a positively biased manner? In an attempt to reconcile inconsistent prior research addressing this question, we predicted that the tendency to form positively biased appraisals of negative experiences may reduce the motive to address those experiences and thereby lead to poorer mental health in the context of negative experiences that are controllable and severe but lead to better mental health in the context of controllable negative experiences that are less severe by promoting positive feelings without invoking serious consequences from unaddressed problems. In 2 longitudinal studies, individuals in new marriages were interviewed separately about their ongoing stressful experiences, and their own appraisals of those experiences were compared with those of the interviewers. Across studies, spouses' tendencies to form positively biased appraisals of their stressful experiences predicted fewer depressive symptoms over the subsequent 4 years among individuals judged to be facing relatively mild experiences but more depressive symptoms among individuals judged to be facing relatively severe experiences. Furthermore, in Study 2, these effects were mediated by changes in those experiences, such that the interaction between the tendency to form positively biased appraisals of stressful experiences and the objectively rated severity of initial levels of those experiences directly predicted changes in those experiences, which in turn accounted for changes in depressive symptoms. These findings suggest that cognitive biases are not inherently positive or negative; their implications for mental health depend on the context in which they occur.