Hypersomnia is characterized by excessive tiredness and difficulty staying awake during the day. Narcolepsy or sleep apnea, sleep deprivation, being overweight, substance abuse, head injuries, mental or neurological (nervous system) diseases, certain medications, or genetics can cause hypersomnia. About 40% of the population shows some symptoms of hypersomnia from time to time. Your doctor can diagnose this condition by talking with you about your sleep habits or using tests such as blood tests, CT scans, or a sleep test. Hypersomnia can be treated with prescribed stimulants or antidepressants, or by lifestyle changes such as avoiding alcohol and medications that cause drowsiness and going to bed early.