Causes of insomnia are various, your lifestyle, physical health, emotional stress or even your sleep environment, could all affect the quality of your sleep. The most common causes of insomnia you can find in the list below:

• Insomnia can be caused by restless leg syndrome. It’s characterized by discomforting sensations felt and need to move the legs or other body parts to relieve these sensations. Restless leg syndrome features worsening of symptoms during the early evening or later at night.

• In case of sleep apnea person's breathing is interrupted during the time of sleep. Each interruption lasts long enough to miss one or more breathing cycles. During this pauses, some part of the sleeper's respiratory tract loses muscle tone and collapses in. People with obstructive sleep apnea usually complain of sleepiness during the day, but they don’t remember their apnea.

• Gastroesophageal Reflux Disease can be cause of repeated awakenings during the sleep because of unpleasant sensations owing to stomach acid that flowing ascending into the throat during sleep.

• Parasomnia includes disorders of arousal or disruptive sleep events such as sleepwalking, nightmares, REM behavior disorder and violent behavior while sleeping. In this case a person moves his/her body in response to events within his/her dreams. Medical intervention can successfully cure parasomnia.

• Mania or Hypomania in bipolar disorder can make process of falling asleep rather difficult. A person going through a manic or hypomanic episode often feels a decreased need for sleep. Sleep deprivation can worsen a manic episode, or cause hypomania to develop into mania.

There are a lot of other causes of insomnia like medications such as decongestants, stimulants (e.g., methylphenidate) and some antidepressants, caffeine, alcohol, nicotine, stress caused by work, death or illness of a family member or friend family life, financial difficulties, anxiety or depression, pain from arthritis of other medical conditions, time zone changes, shift work,
lack of activity during the day. In fact, insomnia is usually considered a symptom of some other condition, rather than a condition itself. It means that everyone should be attentive to symptoms of insomnia.

Besides, a rare genetic condition can cause a prion-based, permanent and eventually fatal form of insomnia called Fatal Familial Insomnia (FFI).