Sleep quality mediates the association between chronotype and mental health in young Indian adults

The research question focuses on the relationship between chronotype (diurnal preference) and mental health, specifically investigating whether this relationship is direct or mediated by other factors like sleep quality, personality traits, and childhood trauma. Previous research has suggested a link between eveningness (preference for late sleep and wake times) and poorer mental health outcomes, including depression, anxiety, and psychosis. However, the exact nature of this relationship remains unclear, with some studies suggesting that the association might be mediated by poor sleep quality. This study aimed to clarify this by examining the chronotype-mental health relationship in a homogenous sample of young Indian adults while controlling for sleep quality, personality traits (neuroticism, schizotypy, impulsivity, and extraversion), and childhood trauma. The hypothesis was that both eveningness and poor sleep quality would be associated with higher levels of depression, anxiety, and stress, with the latter having a stronger association. Further, the study aimed to explore potential interactions and mediating effects of the other measured factors on the chronotype-mental health relationship. The study's importance lies in its potential to provide a more nuanced understanding of the factors influencing mental health in young adults, potentially leading to more targeted and effective interventions.

Existing literature reveals a complex relationship between chronotype and mental health. Studies have demonstrated a link between eveningness and adverse mental health outcomes, such as depression, anxiety, and psychosis. These associations are often linked to personality traits, with neuroticism and impulsivity showing positive correlations with eveningness. Conversely, extraversion tends to be associated with morningness. Furthermore, individuals with a preference for eveningness often report poor sleep quality, characterized by shorter sleep duration, daytime sleepiness, and irregular sleep-wake cycles. Poor sleep quality is also prevalent in various mental illnesses. The role of childhood trauma, particularly emotional abuse, in impacting sleep quality and mental health is also established in the literature. However, the extent to which childhood trauma might influence the chronotype-mental health relationship remains unclear. Some recent studies challenge the direct association between eveningness and poor mental health, highlighting the stronger link between sleep quality and mental health, particularly in females. This existing research creates a context for investigating the mediating role of sleep quality in the association between chronotype and mental health, while also accounting for relevant personality traits and childhood trauma.

This cross-sectional study involved 282 young adults (18-40 years; 195 females) residing in North India. Data were collected between January and March 2023 to minimize seasonal variation. Participants completed self-report measures online in a single session. The Morningness-Eveningness Questionnaire (MEQ) assessed chronotype, the Depression, Anxiety, and Stress Scales (DASS-21) measured mental health, the Pittsburgh Sleep Quality Index (PSQI) assessed sleep quality, the Eysenck Personality Questionnaire-Revised (EPQR-S) and the Short Oxford-Liverpool Inventory of Feelings and Emotions (SO-LIFE) assessed personality traits (excluding the Psychoticism subscale due to low reliability), and the Childhood Trauma Questionnaire (CTQ-SF) assessed childhood trauma. Data analysis included independent samples t-tests to examine sex differences, Pearson's correlations to explore associations between variables, and structural equation modeling (SEM) to examine the mediating role of sleep quality in the chronotype-mental health relationship. The SEM included MEQ scores, personality traits (neuroticism, cognitive disorganization), emotional abuse as predictors, PSQI scores as a mediator, and DASS-21 scores as an outcome variable. Model fit was evaluated using several indices (χ²/df, RMSEA, GFI, AGFI, CFI, TLI). Invariance of the model was tested across males and females.

The study revealed a significant correlation between eveningness and poor mental health (depression, anxiety, stress), but this association was fully mediated by poor sleep quality. Eveningness showed small-to-medium correlations with mental health (r values: 0.20-0.30), whereas poor sleep quality showed medium-to-large correlations (r values: 0.47-0.52). Eveningness was also significantly associated with higher scores on neuroticism, cognitive disorganization, and emotional abuse. The SEM analysis indicated no direct effect of eveningness on mental health (β = -0.001, p = 0.961), with sleep quality fully mediating the relationship (β = -0.10, p < 0.001). Poor sleep quality also partially mediated the relationship between emotional abuse and mental health (β = 0.96, p < 0.001) and between neuroticism and mental health (β = 0.11, p < 0.001), but not cognitive disorganization and mental health (β = -0.04, p = 0.427). Although females showed greater morningness than males, this sex difference did not significantly influence chronotype-mental health associations. While the model showed good fit overall, a significant sex difference emerged in the direct path from cognitive disorganization to mental health (stronger in females).

The findings challenge the notion of eveningness as an independent risk factor for poor mental health, suggesting that its association with mental health is largely explained by its impact on sleep quality. The strong correlation between poor sleep quality and poor mental health underscores the importance of addressing sleep problems to improve mental well-being. The mediating role of neuroticism and emotional abuse highlights the interplay of personality and life experiences in influencing mental health via sleep disturbances. The lack of a direct effect of eveningness on mental health in this study contrasts with some previous research. This discrepancy may be due to differences in sample characteristics, methodologies, or the inclusion of mediating factors like sleep quality. The study’s findings suggest a need to shift focus from altering chronotype to improving sleep quality, particularly in individuals with high neuroticism or history of emotional abuse. Interventions focused on promoting good sleep hygiene could be more effective than attempting to shift diurnal preferences.

This study demonstrates that the relationship between eveningness and poor mental health is fully mediated by sleep quality in young Indian adults. Eveningness itself is not an independent risk factor; rather, its impact on sleep quality is the crucial link to mental health outcomes. This highlights the importance of focusing on interventions to improve sleep quality, rather than solely targeting chronotype shifts, especially in individuals with high neuroticism or a history of emotional abuse. Future studies should investigate these relationships in diverse populations and use objective measures of chronotype and sleep quality to validate these findings.

Several limitations should be considered. The study relied on self-reported measures, which are susceptible to biases. The lack of objective measures of chronotype and sleep could limit the generalizability of the findings. The predominantly female sample limits the ability to generalize findings to males. The study's cross-sectional design prevents causal inferences. Further research is needed to explore the influence of factors such as socioeconomic status, cultural beliefs, and light exposure on these relationships, as well as to investigate these associations across different age groups and cultural contexts. The sample size may also limit power to detect specific effects.