(HealthDay News) -- If you have trouble falling or staying asleep, it's important to understand the reasons for your insomnia.

Here's a list of possible reasons for your sleepless nights, courtesy of the U.S. National Library of Medicine:

* Discomfort or illness.
* Depression.
* Stress or anxiety.
* Drinking caffeine or alcohol, smoking, or taking certain medications or illicit drugs.
* An inappropriate sleep environment, including one that's too bright or too noisy.
* Related activities that affect your sleep, such as taking naps or going to bed too early.