1. Psychological causes: Stress, anxiety, and depression can all lead to insomnia. For example, a student may be too nervous to sleep the night before the examination.
2. Sometimes your “internal clock” becomes confused if you work on shift or travel to another country with different time zone.
3. Consuming drinks with caffeine or other stimulants just before bed-time.
4. Disturbance from external factor such as noise, light and strange odor. A bed that is too hard or too soft, room temperature that is too hot or too cold, or bites from insects such as mosquitoes, flies or fleas.
5. Sudden change in the sleeping environment.
6. Physical factors such as hunger, being too full, frequent urination, coughing, aches and other forms of discomfort.