Advanced melatonin onset relative to sleep in women with unmedicated major depressive disorder

In participants experiencing a major depressive episode, melatonin onset occurred significantly earlier relative to sleep than in controls, with a large effect size.

• Circadian timing in depression shows variability that may relate to diagnosis, medication, and study methods.
• The study involved 48 unmedicated women, including those with major depressive disorder and control participants.
• Earlier melatonin onset relative to sleep is correlated with poorer mood across all participants.
• During a major depressive episode, the body's internal clock is advanced in relation to sleep time.
• Circadian misalignment could play a role in the onset or persistence of major depression.

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