Chronic insomnia (or acute insomnia) is more complex and often results from a combination of factors, including underlying physical or mental disorders.
One of the most common causes of chronic insomnia is depression. Other underlying causes inlcude arthritis, kidney disease, heart failure, asthma, sleep apnea, narcolepsy, restless legs syndrome, Parkinson's disease, and hyperthyroidism.
However, causes of chronic insomnia may also be due to behavioral factors, including the misuse of caffeine, alcohol, or other substances; disrupted sleep/wake cycles as may occur with shift work or other nighttime activity schedules; and chronic stress.
In addition, the following behaviors have been shown to perpetuate insomnia in some people:
Expecting to have difficulty sleeping and worrying about it
Ingesting excessive amounts of caffeine
Drinking alcohol before bedtime
Smoking cigarettes before bedtime
Excessive napping the afternoon or evening
Irregular or continually disrupted sleep/wake schedules
These behaviors may prolong existing insomnia, and they can also be responsible for causing the sleeping problem in the first place. Stopping these behaviors may eliminate the insomnia altogether.