Abstract: Optimism and pessimism are two dimensions of the generalized outcome expectancies. They have been shown to play important roles in predicting depression among various populations. Whereas optimism and pessimism have been repeatedly revealed as two separate constructs, they were viewed as the bipolar opposites in many previous studies. The present study was aimed to examine if optimism and pessimism have distinct roles in depression among university students. Moreover, the moderator effects of stress level were tested to examine the vulnerability hypothesis about the role of optimism proposed in previous studies. The gender differences in the roles of optimism and pessimism were also examined.
Three hundred and thirty-four students (female and male students: 167 in each group) with diverse majors from three universities in Beijing completed questionnaires about their general outcome expectancies, depression and stress. The Life Orientation Test (Scheier, & Carver, 1985) was used to measure students’ optimism and pessimism (Cronbach’α = 0.70), the Chinese version of CES-D (Radloff, 1977) was administered to measure students’ depression (Cronbach’α = 0.87), and a stress rating questionnaire was applied to measure students’ stress level (Cronbach’α = 0.84 ).
The results indicated that optimism and pessimism were significantly but modestly correlated (r = -0.26, p < 0.001). Hierarchical multiple regression analysis showed that while both of them explained unique variance of depression, pessimism explained relatively greater proportion than optimism did. In addition to groups of students who scored higher than average in either optimism or pessimism and lower than average in the other dimension (percentages for the group of optimism and the group of pessimism: 35.9%, 23.4%), there were other groups of students who scored higher than average (19.8%) or lower than average (21%) in both optimism and pessimism. MANOVA further revealed significant group differences in stress and depression. Stress level moderated the relation between optimism and depression in a way that the protective effect of optimism became more salient with increasing stress level. Gender moderated the relation between pessimism and depression to some extent. When stress level was included into the predictive model as a covariate, the negative effect of pessimism was much stronger among male students.
Taken these results together, optimism and pessimism are two related but distinct dimensions of general outcome expectancies, and have different roles in depression. The protective roles of optimism tend to be more important for students with higher stress level, and the destructive roles of pessimism tend to increase for male students with higher level of stress. The vulnerability hypothesis about the role of optimism was not supported

Key words: optimism, pessimism, depression, stress level, gender, moderator effects