Until recently, depression was considered an acute, self-remitting illness of limited duration. However, it is increasingly recognized as a chronic, relapsing, or recurrent illness in most patients, imposing a substantial burden on the individual and society. Research has demonstrated an association between depression and impaired psychosocial functioning, reduced productivity and life satisfaction, excess health care utilization, increased reporting of medically unexplained medical symptoms, comorbidity with other psychiatric illnesses, and suicide. It is more prevalent in patients with common chronic medical conditions, such as obstructive pulmonary disease, hypertension, diabetes, stroke, coronary artery disease, asthma, and chronic pain. In addition to its association with medical morbidity and mortality, depression has a negative impact on self-care behaviors, including medication adherence, in patients with chronic medical illnesses, and in health-related behaviors such as exercise, smoking, and weight control. As a consequence, it is a major barrier to effective care of chronic medical illnesses.

Major depressive disorder (MDD) is a highly prevalent, debilitating disorder that is often chronic, recurrent, and costly, with the economic burden in the United States for the year 2000 exceeding $83 billion. Recent data from the National Comorbidity Survey Replication (NCS-R) indicate that MDD has a lifetime prevalence of 16.2% and a 12-month prevalence of 6.6% in the US. Among those reporting at least one episode of MDD in the previous 12 months, mean episode duration was 16 weeks. Roughly 60% of patients experienced role impairment that was “severe” or “very severe,” and nearly 80% reported comorbid disorders as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, with MDD only rarely being primary. Although 51.6% of patients with MDD received health care treatment for the illness, treatment was “adequate,” as defined by the Agency for Health Care Policy and Research and the American Psychiatric Association guidelines (ie, ≥4 outpatient visits with any type of physician for pharmacotherapy that included use of either an antidepressant or a mood stabilizer for ≥30 days or ≥8 outpatient visits with any professional in the specialty mental health sector for psychotherapy lasting a mean of ≥30 visits) in 41.9% of treated cases. Only 21.6% of all MDD patients in the NCS-R, therefore, received minimal guideline-level treatment.

Depression, which is increasingly regarded as a chronic condition, is associated with significant suffering, social and functional impairment, and an estimated $44 billion in direct and indirect costs annually in the United States. Despite this severe burden on the health care system, the management of depression remains suboptimal in primary care, where many depressed patients fail to receive adequate dosage and duration of treatment. Adherence to evidence-based guidelines, essential to improving outcomes, requires key structural changes to the US health care delivery system. Several health care models aimed at improving treatment adherence in patients with chronic illnesses have been evaluated in primary care settings with promising results. Those approaches that have been found to be effective advocate multifaceted collaborative interventions that target patients, families, physicians, and the organization of the health care system to improve adherence and depression outcomes. Enhancing education and the active participation of patients and their families are now considered important elements of interventions to improve adherence to the treatment of chronic illnesses, including depression.