Disentangling between- and within-person associations of psychological distress and mental well-being: An experience sampling study examining the dual continua model of mental health among university students.

The dual continua model assumes that psychological distress and mental well-being are two related, yet distinct dimensions of mental health. Previous studies did convincingly show the distinctiveness of these two dimensions using mainly cross-sectional research. Despite the importance to distinguish between- and within-person associations in psychological theories, to date, no study specifically distinguished between- and within-person associations for the relationship between distress and well-being. Therefore, the objective of this study was to validate whether the dual continua model actually holds when examined within individuals. Intensive longitudinal data were collected through experience sampling. The sample included 25 university students (mean age = 23.50 years, 56% female), who completed a baseline questionnaire as well as momentary measures of psychological distress and mental well-being three times per day for two weeks. 1,014 timepoints were analyzed using multilevel models and person-mean centering was applied to distinguish between- and within person associations. A significant moderate negative between-person association was found for the relationship between psychological distress and mental well-being (β = -.363, marginal  = 0.15,  < .001). The within-person association was also significant and similar in magnitude (β = -.432, marginal  = 0.18,  < .001) at the group level. Individual within-person associations between distress and well-being varied substantially, but were negative for almost all participants. This study is an important step towards validating the applicability and universality of this widely used model. The current findings provide preliminary evidence that the dual continua model does not only hold between people, but also on the level it is actually used for, namely within individual people.