Everyone has a restless night or two, but insomnia is chronic when it happens at least 3 nights a week for 3 months or more.  The causes of insomnia are generally multifactorial, but can be related to stressful life events, sleeping conditions, bad sleep habits, mental health issues like depression or anxiety, side effects from medications, pain, caffeine, tobacco or alcohol use, hyperthyroidism or other endocrine problems or separate sleep disorders such as sleep apnea or restless legs syndrome.