Treating Comorbid Sleep, Neurological Disorders

The broad pathology of sleep disorders can make diagnosis and treatment complicated.

The range of sleep disorders neurologists treat is wide and includes insomnia, sleep apnea, restless legs syndrome, and narcolepsy.

Primary sleep disorders are caused by endogenous abnormalities in the mechanisms regulating the sleep-wake cycle. Secondary sleep disorders stem from comorbid conditions, including neurodegenerative diseases such as Parkinson’s disease or Alzheimer’s disease, or psychiatric disorders that can cause disruptions in  normal sleep-wake mechanisms.1

At least 40 million Americans suffer from long-term sleep disorders each year, according to the National Institutes of Health. An additional 20 million experience occasional sleeping problems.2

More Americans are seeking help for sleep-related issues, said Andrew Westwood, MD, assistant professor of the clinical neurology division of epilepsy and sleep disorders at Columbia University Medical Center in New York City.

“It is an emerging problem because the population is aging, so the incidence and diagnosis of dementia is increasing in the clinic,” Westwood said. “But also the importance of sleep is becoming well known within the general population, so people are really taking steps to evaluate their sleep. In the past people wouldn’t look at it so carefully.”

Common Comorbid Neurological, Psychiatric Conditions

Evaluating potential primary or secondary causes of sleep disorders can be especially challenging when it comes to neurological disease and psychiatric disorders because the conditions often happen at the same time.

In people who have Alzheimer’s disease, for example, sleep can become fragmented, making it difficult for them to stay asleep. The wakefulness neurotransmitter orexin is elevated in the cerebral spinal fluid of patients with moderate-to-severe Alzheimer’s disease, which could be related to sleep-structure deterioration, according to findings in a recent JAMA Neurology study.3

In Parkinson’s disease, the pathology is different than in Alzheimer’s disease. “You usually see people that are a lot more sleepy or sleepier than the general population or have hypersomnia,” Westwood said. “One of the things you can see in Parkinson’s more than Alzheimer’s is an REM behavior disorder, in which patients actually act out their dreams at night.”

The prevalence of this REM behavior disorder in patients with Parkinson’s disease is believed to be about 15% to 60%. 

Sleep disturbances in mental illness is common. An estimated 20% to 40% of individuals with mental illness experience insomnia. The disorder is an early marker for bipolar disorder and is prevalent in schizophrenia during both psychosis and remission.4

Taking an extensive medical history is the starting point to reveal information about sleep hygiene, sleep patterns, and work or school schedule, according to Westwood.

A physical exam should be performed to make sure there is no evidence to indicate a specific medical condition, such as sleep apnea. A ferritin or T3 blood test can also identify or rule out restless legs syndrome (RLS) or hyperthyroidism.

Using questionnaires (including the Epworth Sleepiness Scale and Beck Depression Inventory), at-home sleep logs, symptom checklists, psychological screening tests, and bed partner interviews are also recommended.5

A clinician who suspects sleep apnea or a movement disorder may order a polysomnogram. This is a comprehensive recording of the biophysiological changes that occur during sleep. This test is usually performed at night, often in a sleep lab.5

Matthew Ebben, PhD, a sleep medicine specialist at Weill Cornell Center for Sleep Medicine at New York-Presbyterian Hospital, said that treating sleep disorders in patients with neurological or psychiatric conditions can be challenging. For example, treatment options for Alzheimer’s patients who have elements of sleep fragmentation are not without hazards.

“You might want to try some hypnotic medications that could help them sleep a little bit, but then you have risk of falls, and patients can become more confused on certain medications. It is a really tricky topic, and there aren’t clear guidelines at this point,” Ebben said.

For psychiatric patients, the sleep disorder and the psychiatric disorder are often intertwined in such a way that it is difficult to know whether to treat the sleep problem first, or whether treating the mental disorder will resolve the sleep issue.

“We know that people with anxiety and depression are at higher risk for developing insomnia, but we also know that people with insomnia may have pre-existing anxiety or depression,” Ebben said. “If you just treat the insomnia, you help the symptoms of depression and anxiety. But there are other studies that show if you focus just on the anxiety or depression, you can also help the insomnia.”

For bipolar disorder, however, the psychiatric disorder is clearly the driver. When a person is having a manic episode, insomnia is only one symptom of a much more complicated problem. In those cases, finding the right mood stabilizer and the right dose to treat the bipolar disorder often improves the insomnia, Ebben said.

Many medications, including zolpidem (Ambien), eszopiclone (Lunesta), zaleplon (Sonata), and non-benzodiazapine hypnotics, can be used to treat insomnia. However, for most people with depression, Ebben said his clinic’s first-line treatment for insomnia is cognitive behavioral therapy (CBT).

“The reason we focus on that is that once you give patients tools to know how to deal with their insomnia in the future, it is a longer-lasting treatment. CBT is also less expensive in the long run, and gives the patient more control,” he added.

Michael O’Leary is a freelance medical writer based in the greater Seattle area.

This article was medically reviewed by Pat F. Bass III, MD, MS, MPH.


  1. Malhotra R, Avidan AY. Neurodegenerative disease and REM behavior disorder. Curr Treat Options Neurol. 2012;14(5):474-92.
  2. National Institute of Child Health and Human Development. “Sleep.” Last update: June 5, 2014. Accessed: Nov. 17, 2014. Available at:
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