Please use this identifier to cite or link to this item: http://bura.brunel.ac.uk/handle/2438/30651
Title: Chronotype and self-reported sleep quality: Effects on mental health and cognitive functions
Authors: Chauhan, Satyam
Advisors: Kumari, V
Norbury, R
Keywords: Chronotype;Sleep;Circadian Rhythms;Mental Health;Cognition
Issue Date: 2024
Publisher: Brunel University London
Abstract: Chronotype is a multidimensional construct underlying circadian rhythms (CRs) of varied mechanisms, including sleep-wake cycles, body temperature, and alertness/arousal levels. It exists on a spectrum from morning (MCs; peak circadian arousal in the morning) to evening chronotypes (ECs; peak circadian arousal in the evening), with most individuals falling in the middle, known as intermediate chronotypes (ICs). Evening chronotype (EC) has been linked with sleep-related disturbances and psychopathology-related personality traits. EC has also been associated with adverse mental, physical and cognitive health outcomes but the roles of sleep-related disturbances and/or psychopathology-related personality traits in this association needs to be clarified. This thesis addressed two broad questions: i) Is chronotype linked to mental health and what is the role of sleep quality in this relationship? To address this question, two psychometric studies were conducted to probe the chronotype-mental health relationship while also quantifying sleep quality and psychopathology-related personality traits (neuroticism, schizotypy, impulsivity) in young non-clinical adults residing in India (N=313), the UK (N=213), or Germany (N=247). ii) Does chronobiological variables [i.e., chronotype, time of day (ToD), synchrony effect] influence neurocognitive functions? First, a systematic review of the existing studies addressing the effects of chronotype, ToD or synchrony effects on cognitive performance was conducted. This was followed by two empirical studies: a) a behavioural study (N=63; age range: 18-40 years) to examine the effect of chronobiological variables and/or sleep quality on verbal learning and memory (immediate recall, recognition, delayed recall), and b) a psychophysiology study (N=45; age range: 18-40 years) to examine the effects of chronobiological variables and/or sleep quality on prepulse inhibition (PPI) of the acoustic startle response (an operational measure of sensorimotor gating function). The findings of the investigations conducted in three independent samples (India, the UK, Germany) showed no direct association between chronotype and mental health in young non-clinical populations. Instead, sleep quality fully mediated chronotype-mental health relationship in these populations. The findings of the systematic review indicated (i) no main effect of chronotype on any cognitive function in most studies, and (ii) a synchrony effect in MCs and/or ECs, mainly but not exclusively in attention, inhibition and memory, in approximately 45% of the studies involving adults aged 18-45 years, and in 80% of the studies involving older (50+ years) adults. The empirical studies conducted as part of this project showed no main effect of chronotype and showed a partial synchrony effect (only in MCs) on delayed recall (episodic memory) but not on PPI (sensorimotor gating) in healthy young adults, most of whom self-reported good sleep quality. In conclusion, the findings show that chronotype does not directly affect mental health and may influence some cognitive functions in interaction with ToD. The findings provide strong support for the sleep hypothesis as a predisposing, precipitating, and perpetuating risk factor for poor mental health and reject the widely reported role of chronotype as an independent transdiagnostic risk factor for mental health problems. The findings also highlight the need for sleep-centred interventions in clinical practices and public health initiatives to improve mental health, and the importance of synchrony (chronotype x ToD) effects when assessing cognitive performance of older adults.
Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London
URI: https://bura.brunel.ac.uk/handle/2438/30651
Appears in Collections:Psychology
Dept of Life Sciences Theses

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