Circadian rhythm dysregulation and morning-predominant anxiety: a systematic review of neurobiological and clinical evidence

Anxiety disorders are traditionally characterized by symptom type and severity; however, growing evidence suggests that anxiety symptoms may also vary systematically across the day. Morning predominant anxiety is frequently reported in clinical practice, yet its circadian and sleep-related underpinnings remain insufficiently synthesized. To systematically review clinical, neurobiological, and population-based evidence examining circadian rhythm dysregulation and diurnal variation in anxiety symptoms, with a particular focus on morning-predominant anxiety. Following the Recommended Reporting Items for Systematic Reviews and Meta-Analyses, a systematic review was carried out. Longitudinal and observational studies that reported morning-predominant anxiety or time-of-day fluctuation were eligible. Twelve studies, including large population-based samples and clinical cohorts, satisfied the inclusion criteria. Anxiety symptoms varied significantly throughout the day, with some people having more severe symptoms in the morning. Increased anxiety was consistently linked to short sleep duration, variable sleep scheduling, and circadian instability, especially in the early hours of the day. Chronotype was found to be a significant modulator, with morning preference seeming to be somewhat protective and evening preference associated with greater anxiety severity and a less favorable diurnal symptom trajectory. Morning-predominant anxiety is a frequent and clinically significant pattern of anxiety symptoms, which frequently shows significant diurnal fluctuation. The time and intensity of anxiety symptoms are influenced by a combination of chronotype, sleep disturbance, and dysregulation of the circadian rhythm.