Sleep, anxiety, and depression: The bidirectional brain-behavior axis.

Sleep, anxiety, and depression are interconnected processes that greatly influence mental health throughout life. Recent studies indicate that sleep issues are not just symptoms of mental illness but can also cause emotional and cognitive problems. Anxiety and depression can disrupt sleep patterns, and ongoing sleep difficulties can raise the likelihood of mood disorders. This reciprocal relationship involves neural pathways, neurochemicals, hormones, immune responses, and social factors. This chapter explores how sleep, anxiety, and depression interact from various scientific and clinical viewpoints. Topics include circadian rhythms, stress hormones, immune signalling, genetic and environmental effects, cognitive impairments, developmental factors, and new treatment options. Understanding these links is crucial for creating comprehensive approaches to simultaneously address sleep and mental health issues.