Major depressive disorder (MDD) is widespread, costly, and frequently chronic. Internationally, the burden of depression is large and growing. By the year 2020, this disorder is projected to be the world's second leading cause of disease burden. The costs associated with depression are enormous; people with depression tend to have approximately double the health care costs of unaffected individuals. There are few other major disorders that have a negative health impact of the same magnitude.

Early onset of depressive symptoms, along with underdiagnosis and undertreatment, contribute to the burden of MDD, which is also characterized by chronicity, frequent relapses, and recurrences. Risk factors for depressive recurrence include the presence of residual symptoms, >3 prior depressive episodes, chronic depression lasting more than 2 years, a family history of mood disorders, other comorbidities (eg, terminal illness, diabetes), and late onset (>60 years of age). Patients who have any of these factors should be candidates for maintenance treatment.

Naturalistic studies have demonstrated that most patients with MDD without sustained treatment will eventually experience a relapse or recurrence. Furthermore, depressive episodes tend to become more autonomous over time, with decreased linkage to stressful life events, more severe, and potentially more refractory with each new relapse or recurrence. Researchers and clinicians have observed that rather than only treat or manage relapses or recurrences of MDD, the best strategy may be prevention of depressive episodes. As a result, current strategies seek to treat patients to remission, which translates to a lower overall risk of developing relapses or recurrences compared with those patients who continue to demonstrate residual symptoms. Thus, a consistent body of evidence now supports continuous pharmacotherapy for the prevention of depressive relapse and recurrence.

One of the most challenging clinical topics in psychiatry is the diagnosis and treatment of bipolar depression. The term mood stabilizer is frequently employed in the treatment of the hospitalized bipolar patient, although clinicians do not universally agree on a consensus definition of this term. Most clinicians would agree that a mood stabilizer refers to a medication that is effective for the acute treatment of manic, mixed, hypomanic, or depressive episodes. Many experts agree that such treatment should offer efficacy against mania, should not worsen depression, and preferably should treat depression as well. In addition, the acute effectiveness in stabilization should not be at the expense of inducing alternate mood symptoms or switching the patient into the alternate phase of illness. From a maintenance standpoint, a mood stabilizer should also prevent against future relapse or recurrence of manic, mixed, hypomanic, or depressive symptoms or episodes (Slide 1).

In addition to use of mood stabilizers, there are other issues surrounding treatment of the hospitalized patient with bipolar depression, including the commonly comorbid issue of substance abuse. Hazardous drinking may more commonly occur in bipolar depression or depressive phase of illness, representing a more complex clinical picture. To facilitate understanding of this complex disorder and its appropriate treatment, this discussion centers around the case of a major depressive episode in a patient with a past history of of mania (ie, bipolar I depression or bipolar depression).