Bright light therapy is primarily used to treat which of the following conditions?

Bright light therapy is primarily utilized for treating circadian rhythm disorders because it helps regulate the body's internal clock, which is often affected in individuals with these conditions. Circadian rhythm disorders include issues such as delayed sleep phase disorder and seasonal affective disorder (SAD), where exposure to bright light can help adjust the timing of sleep patterns and improve overall sleep quality.

By administering bright light during specific times of the day, typically in the morning, this therapy can reinforce the body's natural sleep-wake cycle, encouraging patients to fall asleep and wake up at more socially acceptable times. This is particularly effective since circadian rhythm disorders are directly related to misalignments between the individual's internal biological clock and external environmental cues like light.

Other conditions listed, such as sleep apnea, insomnia, and narcolepsy, have different underlying mechanisms and are treated through various means, including lifestyle changes, medication, or CPAP therapy for sleep apnea, but bright light therapy does not play a central role in their management.