July 2006, Vol. XXIII, No. 8
Difficulties with sleep, including insomnia, provide an opportunity for mental health professionals to venture outside the realms of their respective disciplines. Sleep-related complaints are highly prevalent in our patient populations. These complaints are often presumed to be secondary to coexisting psychiatric disorders. Less appreciated, however, is the potential role of comorbid, and often subtle, medical and neurologic disorders in the genesis of these complaints. The purpose of this article is to help practicing psychiatrists look "outside the box" when a patient reports insomnia. Instead of presuming that sleep difficulties are the result of a patient's primary psychiatric problem or medication used to manage the disorder, a step back to look at all the possibilities may be of greater benefit in producing a definitive resolution of the patient's complaints.
A subjective complaint, insomnia is characterized by repeated difficulty with sleep initiation, duration, consolidation, and quality. It occurs despite adequate time and opportunity for sleep, and is associated with daytime impairments.1 Patients with insomnia rarely report profound daytime sleepiness, characterized by falling asleep during the day at inappropriate times. More often, their complaint is one of fatigue, lack of energy, mental dulling, and a sense of disorientation that they attribute to disturbed, restless, and unrefreshing sleep. Daytime sleepiness, often leading to mishaps and accidents, is a typical consequence of sleep deprivation, whereas insomnia is the inability to obtain sufficient sleep despite the opportunity to do so. The term sleep deprivation implies that too little time is available for sleep and that the opportunity for sleep is therefore curtailed.
MEDICAL AND PSYCHIATRIC CONDITIONS
Insomnia can be associated with several comorbid medical conditions, including diabetes, myocardial infarction (MI), heart failure, angina, any condition that causes chronic pain, prostate disorders, gastroesophageal reflux disease (GERD), and chronic obstructive pulmonary disease (COPD).2 Many of these contribute directly and causally to the development of insomnia (Table 1 [see Psychiatric Times, July 2006, page 9]).3
The relationships among chronic conditions, patient-reported comorbidities, and insomnia were examined using a questionnaire given to 1814 patients who had at least 1 of 5 chronic conditions (hypertension, diabetes, heart failure, MI, and depression) at baseline and again 2 years later. At baseline, mild insomnia was present in 34% of participants, and 16% had severe insomnia. After 2 years, 59% of patients with mild insomnia and 83% of patients with severe insomnia at baseline still had difficulty in sleeping. The odds ratios of conditions present at baseline corresponding to mild and severe insomnia, respectively, were depression, 2.6 and 8.2; subthreshold depression, 2.2 and 3.4; heart failure, 1.6 and 2.5; obstructive airway disease, 1.6 and 1.5; back problems, 1.4 and 1.5; hip impairment, 2.2 and 2.7; and prostate problems, 1.6 and 1.4.
Most of the associations noted at baseline were still present 2 years later.2 The investigators concluded that clinicians should not automatically ascribe insomnia to affective disorders but should also consider the possibility of cardiopulmonary disease, musculoskeletal conditions, and prostate disorders. These findings echo those by Klink and colleagues,4 who conducted a large survey of an adult population to examine the relationship among current complaints of insomnia and obesity, snoring, comorbid medical conditions, and documented complaints of insomnia a decade or more earlier. The strongest risk factor for a current problem with insomnia was a history of insomnia (odds ratio, 3.5). In addition, female gender (odds ratio, 1.5), advancing age (odds ratio, 1.3), snoring (odds ratio, 1.3), and multiple types of comorbid medical conditions (odds ratios, 1.1 to 1.7) also increased the risk of a current complaint of insomnia.
These studies underscore the importance of exploring comorbid medical conditions in patients with insomnia who also have depression, schizophrenia, or an anxiety disorder. Further, it is conceivable that the psychiatric condition of interest developed after a period of insomnia that was initially caused by a medical condition. Many studies that include longitudinal data now demonstrate that the presence of current insomnia predicts future psychiatric conditions, even many years later.5-11
Investigators using data from the National Institute of Mental Health Epidemiologic Catchment Area study questioned nearly 8000 communitysample respondents at baseline and at 1-year follow-up about sleep complaints and psychiatric symptoms. Of this group, 10.2% reported insomnia, and 3.2% reported hypersomnia at baseline. Of those persons with insomnia and hypersomnia, respectively, 40% and 46.5% also had a psychiatric disorder. Only 16.4% of those with no reported sleep problems had psychiatric morbidity. Compared to respondents without insomnia, patients with insomnia at both interviews had a much higher risk for major depression (odds ratio, 39.8). Of particular interest was the finding that the risk of new-onset major depression was much less for those who had insomnia that had resolved by the second visit (odds ratio, 1.6).5
In the Johns Hopkins Precursors Study, a long-term prospective study, investigators examined the relationship between self-reported sleep disturbances and subsequent clinical depression and psychiatric distress in 1053 men who attended medical school at The Johns Hopkins University between 1948 and 1964. Median follow-up was 34 years. The relative risk of new clinical depression developing was greater in those who reported insomnia in medical school (relative risk [RR], 2.0) compared with those who did not. The investigators concluded that insomnia in young male adults indicates greater risk for subsequent clinical depression.7
Restless legs syndrome
One of the most enigmatic medical conditions associated with insomnia is restless legs syndrome (RLS), a sensorimotor disorder with a strong genetic or hereditary component.12,13 Patients experience an urge to move the limbs, especially the legs, and the sensation begins or worsens during periods of rest. Patients use numerous adjectives to describe the sensations, including "creepy-crawly," shock-like, grabbing, and even "Elvis legs."12 The need to move the limbs abates, at least temporarily, if the patient gets up to walk or stretch. Symptoms are more pronounced in the evening or at night than during the day.12
RLS can be confused with several other disorders. It is distinguished from periodic limb movement disorder (PLMD) by the fact that RLS is an office-based diagnosis, while PLMD is definitively diagnosed by polysomnography, during which repetitive bursts of electromyographic (EMG) activity are noted during the course of sleep, typically associated with brief arousals. However, 80% of patients with RLS also have PLMD. RLS is often difficult to distinguish from other medical and psychiatric disorders, such as peripheral neuropathy, whose symptoms may also worsen at night, yet whose symptoms typically do not improve with movement. Nocturnal leg cramps may improve with movement, but they usually are not associated with motor restlessness. Akathisia, a motor restlessness associated with the use of antidepressants, can also closely mimic RLS.
In a study conducted by Montplaisir and colleagues,14 94% of patients with RLS reported difficulty in falling asleep or staying asleep or both. Polysomnography revealed that as symptoms worsened, sleep latency was lengthened, the number of awakenings and arousals increased, and the efficiency of sleep decreased. The condition is common: In a telephone survey of 1800 adults conducted in Kentucky, the experience of restless legs on 5 or more nights per month was reported by 3% of participants aged 18 to 29 years, 10% of those aged 30 to 79 years, and 19% of those 80 years and older. The age-adjusted prevalence was 10.0%.15
Because of their insomnia, many of these patients have poor mental health characteristics, including difficulties with concentration and mental focus, a general feeling of being unwell, and feelings of despondency and depression. Patients with RLS may have suicidal thoughts, marital difficulties, and occupational deficits in addition to depression.14 These psychiatric symptoms and the insomnia complaints, therefore, are caused by a neurologic disorder, highlighting the pitfall of hastily ascribing insomnia to a psychiatric disorder. Massage, hot or cold baths, and distraction techniques have been used with mixed results in some patients with RLS. The only FDA-approved medication for the disorder is ropinirole.
Sleep-related breathing disorders
Obstructive sleep apnea syndrome (OSAS) is characterized by the cessation of air flow while the effort to breathe continues. Spells of apnea are often followed by arousals, with brief periods of increased electroencephalographic frequency from delta or theta to predominantly alpha frequency and/or increased EMG amplitude, which are thought to be important in terminating the apnea and restoring normal breathing. Rarely do these patients present with a complaint of choking or inability to breathe during sleep, which are more indicative of panic disorder and congestive heart failure. More typically, they present with disturbed and unrefreshing sleep, excessive daytime sleepiness, snoring, morning headache and disorientation, memory impairment, irritability, and depression.
Conservative estimates place the prevalence of sleep apnea at 2% to 4% of the population.16 Exacerbating factors include obesity, enlarged neck circumference, middle to older age, male gender, upper airway and craniofacial abnormalities, alcohol and sedative use, smoking, hypothyroidism, acromegaly, and a positive family history.16 Although certain physical characteristicsincluding upper body obesity, neck thickness (17 inches or greater in men; 16 inches or greater in women), hypertension, and obvious airway abnormalitiesraise suspicions of OSAS in a patient who reports daytime sleepiness, irritability, or another suggestive symptom, the diagnosis is made in the sleep laboratory.
OSAS is more prevalent in certain populations, including patients with schizophrenia, of whom 40% to 50% referred for evaluation of sleep complaints have OSAS.17 The prevalence of the condition in other psychiatric populations, such as those with major depression, substance abuse, and bipolar disorder, is not known. The high rate among patients with schizophrenia may be associated with the high prevalence of obesity, a known risk factor for OSAS, in this group of patients. OSAS is associated with a number of risks, such as the development of arrhythmias, hypertension, hypercapnia, cerebrovascular disease, myocardial ischemia, cor pulmonale, and pulmonary hypertension.18,19 An increase in mortality has also been shown to be a function of an increasing apnea index, which is the frequency of apnea episodes per hour of sleep.20
Behavioral interventions for the management of OSAS include weight loss and avoidance of alcohol, sedatives, sleep deprivation, the supine sleeping position, and smoking. Medical interventions include continuous positive airway pressure (CPAP), bi-level positive airway pressure (BiPAP), and oral appliances. Success rates are highest with CPAP and BiPAP. Surgical alternatives attempt to diminish the redundant tissue in the upper airway or to reconstruct the upper airway and bypass it altogether. To date, none of these procedures have attained first-line status for the management of OSAS.