Association between circadian preference and academic achievement: A systematic review and meta-analysis.

The association between circadian preference and academic achievement has been assessed through a systematic review and meta-analysis. The literature searches retrieved 1647 studies; 31 studies, with a total sample size of 27 309 participants, fulfilled the inclusion criteria and were included in the meta-analysis. With reference to all these 31 studies, before running the meta-analysis, the sign of the correlation between the investigated variables was set in a way that a positive correlation showed that eveningness was related to worse academic performance. The meta-analysis yielded a small overall effect size of 0.143 (CI [0,129; 0,156]) under a fixed effects model (Z = 20.584, p < 0.001, I(2)( )= 72.656; Q = 109.715) and of 0.145 (CI [0.117; 0.172]) under a random effects model (Z = 10.077, p < 0.001). A random effects model with a grouping variable (participants) revealed 15 studies based on school pupils and 16 on university students. The random model showed a higher effect size in school pupils (0.166, CI from 0.127 to 0.206) compared to university students (0.121, CI from 0.080 to 0.163). Self-report measures of grades revealed a stronger effect size (0.171; CI: 0.137 to 0.206; N = 20) compared to objective measures (0.093; CI: 0.047 to 0.140; N = 19). Overall, the present results suggest that evening orientation is associated with a worse academic performance, both in school pupils and university students; for the first time, it has been shown that such relationship changes over time, being weaker in university students.