A 19-year-old student complains that he cannot fall asleep before 3 AM even when he goes to bed at midnight, but once asleep he sleeps soundly until 11 AM if undisturbed. His academic schedule requires waking at 7 AM, leaving him chronically sleep deprived. Which intervention best targets the underlying circadian phase abnormality?

• A Bright light exposure immediately on waking in the morning ✓
• B Bright light exposure in the late evening
• C Hypnotic medication at bedtime
• D Daytime napping to repay sleep debt

Explanation

Delayed sleep-wake phase disorder reflects a delayed circadian rhythm. Morning bright light advances the circadian clock and is the mainstay of treatment, often combined with evening melatonin. Evening light would further delay the phase, hypnotics do not shift the clock, and napping does not correct the timing abnormality.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.

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