Because sufferers are partially awakened when this occurs, they rarely experience restorative sleep. They frequently experience compelling motor restlessness resulting in an inability to remain still and when observed sleeping, they engage in spontaneous periodic leg movements. Another identifying characteristic of RLS is that symptoms are almost always worse in the evening or night time. Narcolepsy, a genetic disorder characterized by suddenly and unpredictably falling into REM sleep, is a third medical condition associated with insomnia. Other underlying medical disorders such as asthma, congestive heart failure or pain can also lead to insomnia.
Some research indicates that insomnia can have a genetic component.
Several studies have found that in women, there is a relationship between progesterone hormone levels and sleeppatterns. One-third of insomnia cases are caused by environmental or situational causes such as aging or a disruption in the person's biological rhythm, e.g., jet lag, nap taking, a change in meal times, shift work, etc. Ten to fifteen percent of people with chronic insomnia have an underlying problem that involves the use of drugs, particularly alcohol, and other sedative use. Alcohol, caffeine and other drug use has been shown to impair sleep. Although alcohol in low to moderate doses can initially promote sleep, over the course of the night it interrupts REM sleep.