Outline and evaluate narcolepsy as a sleep disorder (8+16)

Narcolepsy means 'seized by sleepiness', symptoms include; bouts of extreme sleepiness during the day, cataplexy, a loss of muscle tone causing the individual to collapse. These are often brought on by extremes of emotion e.g. excitement or rage. Sleep paralyse may occur which is an inability to move just before falling asleep or waking up. Hypnagogic hallucination may occur when awake making it hard to distinguish between reality and hallucinations. Normally beginning in adolescents or early childhood and may continue throughout life.

One explanation is it is a malfunction in the system that regulates REM sleep. This may explain symptoms such as cataplexy and REM type hallucinations. Cataplexy may be explained through neurons in the medulla, that are normally active during REM sleep, become active while the individual is awake and sends signals to the spinal cord to suppress skeletal muscle movement during waking hours. Another explanation links to lower levels of hypocretin, and narcolepsy, as this is a hormone which promotes wakefulness. Mutations on genes that control hypocretin release have been linked to narcolepsy. 

Nishino et al found those with narcolepsy had lower levels of hypocretin within their cerebrospinal fluid. However, correlational data cannot conclude whether low levels of hypocretin caused narcolepsy or whether it was only a symptom. Low levels of hypocretin have been suggested to have a genetic link however narcolepsy does not always run in families weakening a purely biological explanation to the disorder. Lower hypocretin levels maybe due to environmental factors such as brain injury, infection or a result of an auto-immune attack. To assume that hypocretin is solely responsible for narcolepsy is reductionist as we do not fully understand the complex process, and we may be over simplifying it to out own understanding.

Honda et al suggested another explanation of a link to a mutation in the immune system, linking to Nishino's suggestion of an auto immune attack being a possible cause. Studying narcoleptic patients they found an increased type of HLA. This link was observed in all Japanese patients studies with a similar association of 85% in Caucasians supporting the link. However, in African-Americans this was only present in 65-67% of narcoleptics. Therefore it is likely cultural and biological factors work together to predispose someone to narcolepsy. As this HLA variant was not found in all narcoleptics across cultures it suggests a lack of external validity and limits what generalisations can be made. A criticism for the HLA link is that higher amounts of HLA are present in both narcoleptics and the general population who do not suffer the disorder. Therefore suggesting HLA is the only cause is reductionist as it may be only indirectly involved. 

A psychological explanation may be used in a small number of cases where narcolepsy has been found to run in families. Some form of the disorder may show and cause others to feel sleepy around them e.g. through yawning. Although, when considering the sever nature of symptoms, e.g. cataplexy, a psychological explanation in unlikely to be the cause, and most evidence points towards a biological cause.

Both Nishino and Honda's studies link narcolepsy to a biological cause, but ignores the role of environmental factors, making it reductionist, as these may trigger the disorder. Through such research it is suggested that nature and nurture work together in order to predispose someone to a narcoleptic attack. For example someone with a vulnerability to narcolepsy may need the right environmental trigger e.g. strong emotions for symptoms to show highlighting how the two work together. Therefore both biological and environmental factors will need to be considered in order to help those manage symptoms of the disorder. However, such studies often ignore the role of free will, making it deterministic. If emotional arousal causes its onset then, as we have some level of control over our emotions, we can control it to some extent. Therefore research has positive real world applications as mood controlling therapies such as CBT and self-talk may allow us to better control out emotions therefore we can have a better control of narcolepsy onset.