Diseases of the lung are diverse in pathophysiology, course, and treatment, creating several challenges for the assessment and treatment of comorbid depression. The anxiety associated with shortness of breath—at times nearly indistinguishable from that of a panic—may be the most prominent psychiatric symptom in individuals with lung disease. However, depression of various degrees is also common (Fig. 16-1) and associated with significant morbidity and mortality. This chapter will first review the major classes of pulmonary diseases and the known epidemiology of depression in these groups. Subsequent sections will discuss over-arching pathophysiologic mechanisms, as well as the novel features of depression onset, progression, and treatment in this population.
Ranges of depression prevalence observed in pulmonary diseases.
Asthma, the chronic inflammation of airways characterized by smooth muscle hyper-reactivity, is common, and likely results from a combination of environmental and genetic factors. Worldwide, the prevalence of asthma has risen dramatically in recent years, especially among children and adolescents. In the United States, asthma prevalence increased from 7.3% in 2001 to 8.4% in 2010, making it one of the most common chronic diseases.1 Exercise, infection, allergens, and other airborne irritants can all be associated with the onset of an asthma attack, which is typically marked by wheezing, dyspnea, chest discomfort, and coughing. Although there is no cure, there is effective treatment to prevent and treat acute asthmatic attacks. Depression has been reported in 15% to 50% of individuals with asthma.2–4 Asthma has also been linked to suicidal thoughts, behaviors, and attempts, though the causal mechanisms remain poorly understood.5
Chronic obstructive pulmonary disease (COPD) involves the gradual, progressive narrowing of airways over time, but unlike asthma, these changes are not reversible. The associated tissue pathology may arise from cigarette smoke, other environmental exposures, and/or genetic disposition, such as in alpha-1 antitrypsin deficiency. Progression of COPD may slow sufficiently to allow psychological and social adjustment to the illness, though depression still arises in approximately 20% to 25% of cases, a rate higher than found in the general population.6,7 One study of elderly patients with COPD found rates of clinical depression above 40%.8 Mood may also be acutely worsened by episodic complications of the disease, including infections, hospitalizations, and the need for supplemental oxygen. While depression does not directly correlate with pulmonary function (e.g., percent expected FEV1), there is evidence that mood tends to worsen with advancing stages of disease.9
Cystic fibrosis (CF) arises from one of many autosomal recessive mutations in the CF transmembrane conductance regulator (CFTR) gene. As a consequence, sodium and chloride balance is disturbed across epithelial membranes, most critically in the lungs but also in the liver and pancreas. Diabetes, infertility, and gastrointestinal malabsorption with subsequent malnutrition are all typical complications of CF, ...