^ Hirshkowitz, Max (2004). "Chapter 10, Neuropsychiatric Aspects of Sleep and Sleep Disorders (pp 315-340)" (Google Books preview includes entire chapter 10). In Stuart C. Yudofsky; Robert E. Hales (eds.). Essentials of neuropsychiatry and clinical neurosciences (4 ed.). Arlington, Virginia, USA: American Psychiatric Publishing. ISBN 978-1-58562-005-0. ...insomnia is a symptom. It is neither a disease nor a specific condition. (from p. 322)
Due to rapidly increasing knowledge about sleep in the 20th century, including the discovery of REM sleep in the 1950s and circadian rhythm disorders in the 70s and 80s, the medical importance of sleep was recognized. The medical community began paying more attention than previously to primary sleep disorders, such as sleep apnea, as well as the role and quality of sleep in other conditions. By the 1970s in the US, clinics and laboratories devoted to the study of sleep and sleep disorders had been founded, and a need for standards arose.
If you live in Alaska and think you may be suffering from one of the many sleep disorders listed above, you can take advantage of a free 10-minute phone consultation with the Alaska Sleep Clinic where one of our trained sleep specialists can help determine whether or not you need to have a sleep study to diagnose your condition. To get this free offer click on the link below.
In the UK, knowledge of sleep medicine and possibilities for diagnosis and treatment seem to lag. Guardian.co.uk quotes the director of the Imperial College Healthcare Sleep Centre: "One problem is that there has been relatively little training in sleep medicine in this country – certainly there is no structured training for sleep physicians."[55] The Imperial College Healthcare site[56] shows attention to obstructive sleep apnea syndrome (OSA) and very few other sleep disorders. Some NHS trusts have specialist clinics for respiratory and/or neurological sleep medicine.
Narcolepsy is a brain disorder that causes excessive daytime sleepiness. There is sometimes a genetic component, but most patients have no family history of the problem. Though dramatic and uncontrolled "sleep attacks" have been the best-known feature of narcolepsy, in reality many patients do not have sleep attacks. Instead, they experience constant sleepiness during the day.

What to do: See a doctor, who will likely first check you for underlying conditions related to PLMD. Diabetes, thyroid disorders, anemia, and a number of other conditions can cause PLMD. If you do have another condition, the doctor will treat it and see if the PLMD goes away. The next step is to control the involuntary movements with medication. Drugs that suppress muscle contractions work well for preventing PLMD. The doctor may also prescribe medication to help you sleep more deeply, with the idea of preventing the involuntary movements from keeping you in light sleep.

Recent studies, however, have shown that several factors can interrupt this neurogenesis.[29] These include stress and prolonged sleep deprivation (more than one day).[29] The sleep disturbances encountered in AD could therefore suppress neurogenesis and thus impairing hippocampal functions.[29] This would therefore contribute to diminished memory performances and the progression of AD.[29] And progression of AD would aggravate sleep disturbances.[29] It is a second vicious circle.  

The neurodegenerative conditions are commonly related to brain structures impairment, which might disrupt the states of sleep and wakefulness, circadian rhythm, motor or non motor functioning.[22][24] On the other hand, sleep disturbances are also frequently related to worsening patient's cognitive functioning, emotional state and quality of life.[24][27][28] Furthermore, these abnormal behavioural symptoms negatively contribute to overwhelming their relatives and caregivers.[24][27][28] Therefore, a deeper understanding of the relationship between sleep disorders and neurodegenerative diseases seems to be extremely important, mainly considering the limited research related to it and the increasing expectancy of life.[22][28]

Women often experience sleepless nights and daytime fatigue in the first and third trimesters of their pregnancy. During the first trimester, frequent trips to the bathroom and morning sickness may disrupt sleep. Later in pregnancy, vivid dreams and physical discomfort may prevent deep sleep. After delivery, the new baby's care or the mother's postpartum depression may interrupt sleep.
The natural internal clock that controls our 24-hour cycle of sleep and waking, circadian rhythms are easily upset by changes in schedule, and they're greatly affected by light and darkness. Jet lag is the best known circadian rhythm disorder, but this sensitive inner clock can also be disrupted by changes in routine resulting in an erratic sleep schedule.