As with most brain-related questions there is no direct evidence or cause as to the exact underlying mechanism for what makes us sleepwalk, but nevertheless there has been some interesting research into this area. You may be aware that there are different stages to the sleep cycle and it has been found that physical activity – including sleepwalking – only occurs during the non–rapid eye movement (NREM) cycle of deep sleep.
It is thought that sleepwalking occurs due to normal physiological systems being activated by the brain at inappropriate times. Research has shown that there may be genetic involvement which means tendencies to sleepwalk can be passed on from one generation to the next. It has also been observed that sleepwalking occurs most often in childhood, which could be to do with children spending more time on average in the deep sleep part of the sleeping cycle. Several studies have shown that sleepwalking can be associated with stress, fever and sleep deprivation.
There is a chemical messenger in the brain called gamma-aminobutyric acid (GABA), which acts as a neural inhibitor to certain activity of the brain. It has been speculated that a lack of this, or an underdeveloped system which inhibits the activity of the brain, could be a cause.