Which supplement is commonly used for insomnia?

• A. Melatonin
• B. St. John's Wort
• C. Garlic
• D. Black cohosh

Answer: (A)

The thing this item tests is how sleep-wake timing can be helped by a supplement that mirrors a natural hormone involved in signaling sleep. Melatonin is commonly used for insomnia because it directly influences the body’s circadian system. Taking a small amount can help advance the sleep onset when the internal clock is misaligned or when difficulty falling asleep is prominent, such as with jet lag or shift-work-related sleep problems. It’s not a stimulant and is generally well tolerated in the short term, and it doesn’t carry the same dependency concerns as many prescription sleep meds.

The other options target different issues: St. John’s Wort is mainly used for mood disorders and has many drug interactions; garlic is considered for cardiovascular health; black cohosh is used for menopausal symptoms. None of those primarily address the sleep-wake timing mechanism the way melatonin does.