What causes insomnia?

Common causes of insomnia include work stress, relationship issues, or traumatic events. Often times, insomnia occurs in response to certain medical conditions, medicines, and other sleep disorders (e.g., obstructive sleep apnea). Caffeine, tobacco, alcohol, and other substances can also trigger insomnia. However, in some cases, insomnia is considered to be a primary problem because it does not have an identifiable cause, although risk factors include long-lasting emotional upset, stress, travel, and shift work.^[1]