Psychologiocal explanations - Lehrman (1943) suggested sudden attacks of sleepiness disguise sexual fantasies
REM - a common symptoms is cataplexy (loss of muscle tone) which usually happens in REM. at night narcoleptics have abnormal REM sleep so narcolepsy could be a malfunction of the system that regulates REM.
HLA - in 1980 it was suggested narcolepsy was due to a malfunction of the immune system. Honda et al (1983) found increased frequency of one type of HLA (found on white blood cells). its found 90% of narcoleptics with ctaplexy have this varient.
Hypocretin - hypocretins (neurotransmitters) regulate sleep and wakefulness, normally there are 10,000-20,000 hypocretin-producing cells but in narcoleptics many of these are missing; resultingn in low levels of hypocretin.
REM - Vogel (1960) found in narcoleptic patients REM happened at the onset opf sleep rather than later in the cycle.
HLA - the HLA varient isnt found in all narcoleptics, it can also be found in non-narcoleptic ps; showing this isnt the only variable.
Lin et al (1999) found a muation of chromasone 12 in narcoleptic dogs which disrupts the processing of hypocretin. this has also been conforimed in human studies.
Mignot (1998) found its unlikely low levels of hypocretin are genetic. and are more likely to be due to stress, illness or injury.
a HLA varient could also cause lower levels (Mignot).
Real life application - although research into the effect of lower levels of hypocretic help lead to a treatment, it hasnt been successul so far as the hypocretic molecule is unstable and therefore often breaks down before reaching the brain.
Incomplete arousal - the person is partially awake that they can egage in activities however are also in SWS. recordings of brain activities show delta waves (SWS) and beta waves (awake) suggesting they are in a state of incomplete arousal.
Risk factors - sleep deprivation, alcohol, fever, stress etc. however as risk factors only cause sleep walking in some people suggests there is another reason.
Childhood - may be due to children having more SWS. Oliviero (2008) found the system that usually inhibits motor activity in SWS is not sufficiently developed in some children and may also be in some adults. Oliviero examined the motor excitability of adult sleepwalkers during wakefulness, compared to controls they showed immaturity.
Sleep walking evaluation
Genetic basis - Broughton (1968) found sleep walking in first degree relatives is 10X higher than in the general population.
Diathesis stress model - Zadra (2008) studied 40 ps who sleepwalk. they were prevented from sleeping in a sleep lab on the first night 50% sleep walked, on the second day 90% did. as sleep deprivation doesnt affect everyone like this it suggests some people are vunerable.
psychological cause - one belief is that the person is acting out dreams and anxieties, however this is unlikely because sleepwalking occurs in SWS.
real life application - October 2003 Jules Lowe attacked his 82 year old father and claimed he was sleep walking. due to research, tests were able to show he did have a history of sleep walking and was sent to a psychiatric ward.