Types of Insomnia
There are two types of insomnia. The most common type is called secondary insomnia. More than 8 out of 10 people with insomnia are believed to have secondary insomnia. Secondary means that the insomnia is a symptom or a side-effect of some other problem. Some of the problems that can cause secondary insomnia include:

• Certain illnesses, such as some heart and lung diseases
  
• Pain, anxiety, and depression
  
• Medicines that delay or disrupt sleep as a side-effect
  
• Caffeine, tobacco, alcohol, and other substances that affect sleep
  
• Another sleep disorder, such as restless legs syndrome; a poor sleep environment; or a change in sleep routine
  

In contrast, primary insomnia is not a side-effect of medicines or another medical problem. It is its own disorder, and generally persists for least 1 month or longer.