Chronotype, depression and public health

When the biological clock affects the mental health

Abstract

Chronotype refers to an individual’s biological preference for specific sleep–wake and daily activity schedules and represents an expression of circadian system functioning. Far from being a mere habit, chronotype has genetic and physiological bases and is associated with multiple cognitive, emotional, and health-related processes. Over recent decades, scientific evidence has consistently shown that the evening chronotype is associated with a higher prevalence of depressive symptoms and a significantly increased risk of depression compared with the morning chronotype. This relationship is partly explained by the misalignment between internal biological time and socially imposed schedules, a phenomenon known as social jet lag, which promotes chronic sleep deprivation, irregular daily rhythms, and neuroendocrine alterations involved in mood regulation. Beyond depression, the evening chronotype has also been linked to other adverse health outcomes, including anxiety, substance use, obesity, and cardiometabolic diseases. In the Mexican context, although evidence remains limited, studies in adolescents have associated circadian preference with depressive symptoms and suicidal ideation, while clinical literature has documented circadian system disruptions and altered melatonin secretion in individuals with depression. From a public health perspective, integrating chronobiological knowledge into mental health prevention and health promotion strategies offers an opportunity to rethink the relationship between biological time, social organization, and emotional well-being, and to develop population-level interventions aimed at reducing the burden of depression and other conditions associated with circadian misalignment.