These include insomnia, narcolepsy, sleep apnea, night terrors, and others. Insomnia Insomnia is the inability to get a good night sleep. There are individual differences in how much sleep a person requires. Thus, a person sleeping only 4-5 hours a night is not necessarily suffering from insomnia, it may simply be that individual's circadian rhythm differs from the norm. Insomnia is strictly a case of not getting enough sleep, what ever that amount may be for an individual.
Some drugs can aggravate insomnia.
Use of alcohol for example can cause insomnia. People who get into the habit of taking sleeping pills are insomniac. Narcolepsy The opposite of insomnia is narcolepsy. The expression of narcolepsy is a sudden and unexpected periods of sleep. The person may be sitting at the dinner table and drop into sleep and after a brief period wake up again.