OSA is common in both clinical and general populations. The estimated prevalence of OSA in Veterans Health Administration patients is 2.91%.13 This compares well with the 2.1% prevalence observed in a general population, cross-sectional telephone survey in Western Europe.14 However, approximately 20% of patients with MDD also have a breathing-related sleep condition.15 The converse relationship yielded a similar concurrence rate. These data confirm that depressed patients are at higher risk for sleep apnea.
While OSA and depressed mood commonly occur together, it is unclear whether depression is a primary process or the manifestation of disordered sleep. Excessive daytime sleepiness, impaired concentration, low libido, memory difficulties, and neuropsychological testing deficits are among the consequences of OSA. These symptoms overlap with MDD. Treatment of both disorders are needed to minimize their effects on the patient.
The diagnosis of OSA requires referral to a sleep specialist who can perform a specialized physical examination and who has access to a sleep laboratory for polysomnography. For financial and logistical reasons, it is not feasible to send every depressed patient for full-night polysomnography. While limited studies (nonneurophysiological recording of sleep and oxygenation patterns) have been used, polysomnography provides more definitive exclusion or confirmation of OSA. One study evaluated an optimal screening process based on patient symptoms that would initiate a more formal sleep evaluation.16 When severe snoring, observed apnea during sleep, or excessive daytime sleepiness is endorsed, referrals for polysomnography will yield sleep apnea rates up to 60%.
Eating disorders and TRD
Depression and eating disorders are known to be highly comorbid. In a critical review of the literature on the comorbidity of depressive disorders and eating disorders, Godart and colleagues17 determined that comorbidity rates for bulimia nervosa and depressive disorders range from 24% to 90%; for anorexia nervosa, comorbidity rates range from 31% to 89%. In fact, patients with bulimia not only had higher lifetime prevalence rates of depression than controls, but they also had higher rates than patients with bipolar disorder or schizophrenia.
Presnell and colleagues18 found that bulimic symptoms were predictive of future depressive symptoms. Persons with eating disorders had significantly higher scores on the Beck Depression Inventory than controls and those who have chronic pain.19 The severity of disordered eating symptoms and that of depressive symptoms is highly correlated. In addition, as the eating disorder symptoms improve and resolve, so do the mood symptoms.17 In a prospective study, Angst and colleagues20 followed patients over 20 years to characterize differences between episodic depression and long-term depression. Binge eating was more common in the group with long-term depression.
However, in anorexia nervosa, the direct effects of starvation may confuse the diagnosis of depression. Persons with anorexia often have depression-like symptoms, including fatigue, poor sleep, lack of interest in sexual activity, and flat mood.21 With chronic disordered eating, feelings of helplessness and hopelessness also often become prominent. In a study of 70 patients, Coughlin and colleagues19 showed that psychological complications related to disordered eating worsened the longer the starvation or binge-purge behavior lasted. Primary efforts toward nutritional restoration and development of healthy eating patterns should play a critical role in these patients. In 4 placebo-controlled trials, there was no evidence that antidepressants had a positive effect on weight gain, the eating disorder, or associated psychopathology.22
TRD is difficult to affirm in patients with low body weight. Correction of the eating disorder, especially in malnourished patients, may allow better attribution of depressive symptoms to an underlying mood disorder. In addition, establishing the timeline of a depressive disorder in relation to an eating disorder through detailed history and collateral reports may help justify continued antidepressant use in the midst of an eating disorder. In normal-weight patients with disordered eating, antidepressants are likely to be more effective.
Factors that contribute to TRD are not limited to those described in this article. Substance and alcohol(Drug information on alcohol) abuse or dependence often elude an initial evaluation and undermine even the most aggressive antidepressant strategies. In addition, interactions with prescribed medications—not just drugs of abuse—can alter pharmacodynamics and/or pharmacokinetics, which necessitates closer monitoring and possible dosage adjustments.23
On the medical side, several conditions besides sleep apnea are associated with depression.24 Vigilant efforts to detect and treat anemia, hypothyroidism, heart disease, or even occult cancer remove barriers to depression treatment and improve a patient’s overall health. In addition, the issue of the relationship of chronic pain to depression is a complex one deserving of attention.
Editor’s Note: Our Category 1 CME articles are on hiatus for the summer. In the meantime, we invite you to test yourself: read the article, take the posttest on the next page, and then check the answer key on the last page of this article for the correct answers.