What are the 4 biggest sleep disorders? INSOMNIA • SLEEP APNOEA • RESTLESS LEGS • NARCOLEPSY Find out more from health24.com: 1. Insomia Definition: Trouble falling or staying asleep at least three nights a week for three months or longer. Signs: Daytime fatigue; moodiness; problems with attention and memory; anxiety about sleep. Causes: Stress; depression; alcohol and/or caffeine use; substance abuse; irregular sleep schedule. Try first: Cognitive behavioural therapy for i