Insomnia — substances to eliminate

• A. Marijuana
• B. Oral contraceptives
• C. Caffeine
• D. Thyroid preparations

Answer: (C)

Caffeine is a classic factor to eliminate when addressing insomnia because it is a central nervous system stimulant that disrupts sleep by blocking adenosine receptors, which reduces sleep pressure and can delay bedtime, shorten sleep duration, and increase awakenings. Because caffeine can affect sleep even if consumed many hours before bed, reducing or removing it—especially in the afternoon and evening—often leads to clear improvements in sleep onset and overall sleep quality.

Other substances can influence sleep for some people (hormonal contraceptives or thyroid medications can affect sleep in certain individuals, and marijuana may alter sleep patterns), but caffeine has the most consistent and widespread impact on insomnia, making it the primary target to eliminate.