Impact of Circadian Rhythm Disturbance and Chronotype on Medical Students' Mental State.

Introduction: Shift workers usually undergo circadian misalignment, which appears when the feeding and sleep-wake cycles are desynchronized with the temporal framework organized by the internal biological clock. People differ considerably in their tolerance to shift work depending on their chronotype. This research aimed to obtain information about circadian disorders and chronotype (as a mediating variable) on consequent mental states such as impulsivity, depression, anxiety, stress, addiction potential, and boredom in students of a medical university in northeastern Iran. We studied the mental state of individuals with circadian misalignment and compared it with the healthy control group.

Methods: The study design is a double-blind, randomized, controlled clinical trial. Thirty-five participants were randomly assigned to circadian alignment/misalignment protocols. Subjects completed questionnaires as baseline data (pre-test) and the end of the interventions (post-test). The study instruments were the multidimensional state boredom scale (MSBS), addiction potential scale, depression, anxiety, and stress scale-21, and Barratt impulsiveness-11 (BIS-11). To analyze outcomes, we categorized participants based on chronotype as mediate variable within each group (circadian aligned and misaligned condition).

Results: The mean age of the participants was 21.66 years (range: 18-25 years). One-way analysis of variance to compare research variables in groups based on chronotype (evening, intermediate type, and morning types) showed a significant difference between the three chronotype groups in the total and non-planning impulsivity, as well as active and passive addiction potential (P<0.001). The Bonferroni post hoc test was used to compare the mean of variables in the chronotype groups about total and non-planning impulsivity scores, as well as active and passive addiction. The results showed that non-planning (P<0.01) and active addiction (P<0.001) in people with evening and intermediate types were significantly lower than in people with morning type (P=0.02).

Conclusion: Alterations in diurnal profiles of activity, sleep, and feeding time, based on chronotype related to impulsiveness and boredom, and such circadian misalignment were associated with addiction potential.