Traditionally, chronotype has been conceptualized within a single morningness-eveningness continuum. However, emerging evidence suggests that a multidimensional approach may better reflect circadian functioning. This review aimed to examine the associations between chronotype characteristics derived from the leading multidimensional model, as measured by the Morningness-Eveningness-Stability Scale improved, and mental health-related outcomes in adults. A systematic search was conducted across four databases. Of 151 screened records, 20 studies comprising 11 681 adult participants met the inclusion criteria and were included in the final analysis. Pearson's correlations were used as effect sizes, and random-effects models were applied for the meta-analysis. The three dimensions of chronotype showed distinct patterns of association with mental health-related outcomes. Morning affect (MA) was associated with lower levels of ill-being and higher levels of well-being, whereas Distinctness (DI) showed the opposite pattern. Within the available MESSi literature, Eveningness (EV) showed weaker and less consistent associations with the examined outcomes than MA and DI. Meta-analytic findings indicated that MA and DI were more strongly and consistently associated with the examined mental health-related outcomes than EV. Overall, these findings support a multidimensional conceptualization of chronotype and suggest that aspects of circadian functioning beyond eveningness may be important for understanding individual differences in mental health-related outcomes.
