Sleepwalking or somnambulism runs in families, indicating a genetic component. Studies show that it is also associated with sleep deprivation, fever, stress and intake of drugs, especially sedatives, hypnotics, antipsychotics, stimulants and antihistamines. Somnambulism occurs because normal physiological systems are active even at inappropriate times. Why the brain issues commands to the muscles during certain phases of sleep is not known, but these commands are usually suppressed by other neurological mechanisms. At times this suppression can be incomplete and actions that normally occur during wakefulness emerge in sleep.
In children, it is believed to be related to fatigue, prior sleep loss or anxiety. Children, mostly aged six to 12 years, are afflicted, perhaps because they spend more time in the “deep sleep” phase of slumber.
Physical activity happens only during the non-rapid eye movement (NREM) cycle of deep sleep, which precedes the dreaming state of rapid eye movement (REM) sleep. During this phase, the body releases a chemical that paralyses the body. However, sleepwalkers do not have this chemical trigger, hence the behaviour. With several cycles of non-REM and REM sleep in a night, sleepwalking occurs mostly during deep non-REM sleep early in the night or near morning.
In adults, sleepwalking is associated with a disorder of the mind but may also be seen with reactions to drugs and/or medications and alcohol, and medical conditions like partial complex seizures. In the elderly, it may be indicative of an organic brain syndrome, REM behaviour disorders or a personality disturbance.