Psychophysiological Pathways Linking Physical Activity and Mental Health in Adolescents: A Narrative Review of Autonomic Regulation, Hypothalamic–Pituitary–Adrenal Axis Function, Neuroplasticity, and Sleep Rhythms

ABSTRACT: Adolescence is a crucial developmental stage marked by rapid biological maturation, intense social scrutiny, rising academic pressures, and ongoing development of brain systems linked to reward processing, executive control, stress regulation, and emotion regulation. Depressive symptoms, anxiety, perceived stress, sleep problems, sedentary behavior, and excessive screen exposure often occur during this time. Research has extensively explored physical activity as a modifiable behavior that could enhance adolescent mental health, but much of the evidence still focuses on its link to improved psychological outcomes. Less attention has been given to the psychophysiological pathways through which physical activity may impact mental health. This narrative review examines how physical activity affects adolescent mental health, focusing on autonomic nervous system regulation, HPA axis function, inflammatory and immune pathways, neuroplasticity, and sleep–circadian rhythm regulation. There is evidence that suggests physical activity may support adolescent mental health by increasing autonomic flexibility, facilitating stress recovery, boosting neurotrophic signaling, improving executive control and sleep quality, and fostering social connections, while reducing sedentary time and inflammatory burden. However, these effects are not uniform. Factors such as gender, pubertal development, initial mental health status, body weight, fitness, activity preferences, family support, school climate, peer connections, digital lifestyle, and activity dose might all impact the psychological and physiological outcomes. This review makes the case that physical activity shouldn’t be used as a panacea for adolescent mental health problems. Rather, this should be interpreted as a developmentally integrated psychophysiological regulation approach whose benefits depend on dose, timing, context, individual variation, and its combination with sleep, stress management, and supportive social environments.