Many of the causes of  insomnia :

• Jet lag
   
• Changes in shift work
   
• Excessive or unpleasant noise
   
• Uncomfortable room temperature (too hot or too cold)
   
• Stressful situations in life (exam preparation, loss of a loved one, unemployment, divorce, or separation)
   
• Presence of an acute medical or surgical illness or hospitalization
   
• Withdrawal from drug, alcohol, sedative, or stimulant medications
   
• Insomnia related to high altitude (mountains)

Other causes of insomnia

• Common stimulants associated with poor sleep include caffeine and nicotine. You should consider not only restricting caffeine and nicotine use in the hours immediately before bedtime but also limiting your total daily intake.
   
• People often use alcohol to help induce sleep, as a nightcap. However, it is a poor choice. Alcohol is associated with sleep disruption and creates a sense of nonrefreshed sleep in the morning.
   
• A disruptive bed partner with loud snoring or periodic leg movements also may impair your ability to get a good night's sleep.

insomnia is caused by another disease or psychological problem. In this case, medical or psychological help may be useful. The most commonly used class of hypnotics prescribed for insomnia are the benzodiazepines. These are minor sedatives and include drugs such as temazepam, diazepam, lorazepam, nitrazepam and midazolam. These medications can be addictive, especially after taking them over long periods of time.Non-benzodiazepine prescription drugs, including the Ambien and Lunesta, are quickly replacing benzodiazepines as a first-line treatment for insomnia, as these drugs show little to no possibility of addiction or dependence. Some antidepressants such as mirtazapine, trazodone and doxepin have a sedative effect, and are prescribed off label to treat insomnia. Low doses of Atypical antipsychotics such as quetiapine (Seroquel) are also prescribed for their sedative effect.