Discuss explanations for insomnia and narcolepsy (24 marks)

Discuss explanations for insomnia and/or narcolepsy (8+16)

Explanations of narcolepsy are mainly due to a biological cause, possibly caused by a lack of hypocretin. The neurotransmitter hypocretin regulates sleep and wakefulness through interactions that regulate homeostasis in the hypothalamus (Sakurai 2007). A lack of this neurotransmitter may explain the sudden attacks of sleep. This was seen with Mignot et al who found low levels of hypocretin in patients with narcolepsy. Initially Mignot studied dogs that had low levels of hypocretin and identified the gene and receptor for hypocretin as well as a genetic mutation, which resulted in reduced hypocretin levels in narcoleptic dogs.

Supporting evidence for this theory comes from Moore who found that hypocretin producing cells in the hypothalamus were reduced in narcoleptic patients. In dogs they found that a mutation produced this lack of hypocretin but this is not true in humans. Despite this a link has been established between an antigen – HLA and low levels of hypocretin. 90% of narcoleptics have an increased variant of the HLA antigen which causes low levels of hypocretin and therefore narcolepsy. As a result, narcolepsy may be an autoimmune disorder rather than a problem with neuroanatomy.

In addition, another explanation for narcolepsy could be explained by a malfunction in the system which regulates REM sleep. A classic symptom of narcolepsy is the loss of muscle tone (cataplexy) which is similar to what happens during REM sleep. In addition, during the daytime, narcoleptics often experience intrusions of REM-type sleep (hallucinations), yet at night they have abnormal REM sleep.  Therefore an explanation is that narcolepsy is due to a faulty REM mechanism.

Vogel supports this theory as he found that people with narcolepsy experience REM at the onset of sleep, often going straight into REM from waking during bouts of unexpected day time sleep, which explains the symptoms of narcolepsy. However, despite this evidence, general research support for this explanation is not particularly convincing. The study provided a correlation between narcolepsy and faulty REM, thus producing results in low external validity because it doesn’t confirm whether narcolepsy is a symptom or cause.

Alternatively, one biological explanation of insomnia is due to a person’s genetics. A family history of persistent difficulties with sleep indicates that the disorder may be inherited. The gene, or combination of genes, may prevent the neural mechanisms that control sleep from operating. Idiopathic insomnia is a rare form of chronic insomnia which is present from birth with no obvious cause and is thought to…