Understanding Hypersomnolence Disorder
People affected by hypersomnolence disorder have unusual levels of daytime sleepiness that interfere with their ability to successfully fulfill their responsibilities or otherwise participate in their normal routines. However, they don’t have a condition called narcolepsy, which causes a specific, unrelated form of daytime sleepiness.
DSM IV, the edition of the Diagnostic and Statistical Manual that was current before the 2013 publication of DSM 5, contained a category of conditions called primary sleep disorders. Ailments in this category all featured sleep-related difficulties that stem from problems originating directly within the body, rather than from outside interference or the secondary effects of other health problems. In addition to primary hypersomnia, conditions listed as primary sleep disorders included narcolepsy and primary insomnia. DSM 5 eliminates the primary sleep disorder category and places hypersomnolence disorder, narcolepsy and the renamed insomnia disorder in a new category of conditions called sleep-wake disorders.
According to the DSM IV, people affected by primary hypersomnia have levels of daytime sleepiness that significantly interfere with their daily routines or mental well-being for at least 30 days. They also lack other sleep-related problems—such as insomnia, narcolepsy, or circadian rhythm sleep disorder—that might provide a reasonable explanation for their unusual sleepiness. In addition, their symptoms don’t stem from the effects of any other mental health concern, from a physical problem or from the side effects of medication or drug use/abuse.
There is another form of hypersomnia, called secondary hypersomnia. People with this form of the disorder develop excessive daytime sleepiness as an indirect consequence of some other mental or physical health problem. The Hypersomnia Foundation lists potential causes of secondary hypersomnia that include the mental/physical disorder obstructive sleep apnea, chronic fatigue syndrome, various forms of diagnosable depression, Parkinson’s disease, certain infectious illnesses and kidney failure.
Hypersomnolence Disorder Basics
On a practical level, both primary hypersomnia and secondary hypersomnia can produce the same negative effects on a person’s mental well-being and ability to function. In essence, DSM IV omitted this critical fact by only creating a definition for primary hypersomnia and excluding secondary hypersomnia from official consideration as a mental health concern. DSM 5 corrects this situation by eliminating primary hypersomnia as a diagnosable condition and replacing it with hypersomnolence disorder. Unlike the criteria for primary hypersomnia, the criteria for hypersomnolence disorder don’t use the presence of secondary hypersomnia-related problems as a reason for not making an official diagnosis.
The creation of hypersomnolence disorder forms part of a larger process that affects all sleep-related conditions defined as mental disorders by the American Psychiatric Association, which oversees publication of the Diagnostic and Statistical Manual. As was true with primary hypersomnia, DSM IV based the criteria for diagnosing all other sleep-related problems on the nature of the source of those problems. According to these criteria, conditions with a known underlying psychological or physical cause were excluded from consideration, and doctors could only officially diagnose conditions that had no major psychological or physical link to other ailments. DSM 5 gets rid of these restrictions for all sleep-related mental health conditions and lets doctors diagnose them based mainly on their effects, rather than on their causes. In line with this change, the condition once known as primary insomnia is now known as insomnia disorder.
Hypersomnolence Disorder Vs. Narcolepsy
Both hypersomnolence disorder and narcolepsy produce excessive daytime sleepiness. However, DSM 5 maintains the separation between narcolepsy and other forms of hypersomnia. The main reason for this distinction is the fact that the vast majority of narcolepsy cases have a single underlying cause: unusually low levels of two brain chemicals, called hypocretin-1 and hypocretin-2, which normally help regulate sleepiness. Apparently, roughly 90 percent of all narcoleptics have an autoimmune disorder that mistakenly causes the immune system to attack and destroy the brain cells responsible for making the hypocretins. About 10 percent of all people affected by narcolepsy have normal levels of hypocretin-1 and hypocretin-2 in their brains. No one knows why these individuals develop the disorder, the Stanford School of Medicine’s Center for Narcolepsy reports.