Willing to Donate? A Quantitative and Thematic Analysis of Attitudes to Deceased Organ Donation in Different Circumstances.

Sleep and obesity are bidirectionally associated through both physiological and behavioural mechanisms []. Poor sleep disrupts hormonal regulation, including reductions in leptin and increases in ghrelin [, ], which influence appetite and energy balance []. Elevated cortisol levels associated with insufficient sleep may contribute to stress‐related metabolic changes and fat accumulation, further increasing the risk of weight gain [, ]. Conversely, obesity and related metabolic dysfunctions can impair sleep quality and duration through mechanisms such as sleep apnoea [], inflammation [] and disruptions in circadian rhythms []. Systematic evidence also highlights the role of pre‐sleep behaviours, including poor sleep hygiene, inconsistent bedtime routines, a later chronotype, delayed sleep onset, and social jetlag, as factors associated with obesity in adolescents []. Despite these established associations, current obesity interventions often prioritise dietary and physical activity modification [, , ], with sleep remaining relatively underused as an intervention target [, , ]. Adolescence is a period marked by rapid physiological, behavioural, and social change, during which both sleep patterns and body weight undergo significant transitions [, , ]. In adolescents experiencing pubertal hormonal shifts, these sleep and weight‐related changes occur alongside major shifts in behaviour, including increasing mental health concerns [], independence over eating patterns [, ], screen use [, ], physical activity [, ], social routines and risk‐taking behaviours [, ]. Identifying shared behavioural determinants of poor sleep and obesity is essential for developing integrated interventions []. A recent systematic review highlighted socio‐environmental determinants (e.g., gender, ethnicity, pubertal status, academic attainment), behavioural factors (e.g., timing of physical activity, unhealthy dietary choices and their timing, screen time, and video gaming quantity and timing) and health determinants (e.g., wellbeing) associated with sleep and obesity in adolescents aged 8–18 years []. These findings suggest that sleep and obesity may be influenced not only by the quantity of health behaviours but also by their timing, context and clustering during adolescence. This is particularly relevant because adolescence is characterised by increasing autonomy, changing peer influence and less caregiver‐directed routines, which may shape eating timing, screen use, physical activity and engagement in health‐risk behaviours [, ]. While risk‐taking behaviours, such as smoking and alcohol experimentation, were not identified as a primary determinant domain in the systematic review, they may be relevant to examine because they are associated with self‐regulation, decision‐making and broader patterns of health behaviour [, , ]. Similarly, digital access and online activity behaviours may be relevant because screen‐related effects on sleep and weight status may depend on timing, location, content and caregiver monitoring, rather than total screen time quantity alone []. Examining these behavioural domains together may therefore help identify whether specific behaviours act as shared determinants of both sleep duration and body mass index percentile ([]) during adolescence.