Understanding Unipolar Depression
Unipolar depression refers to major depressive disorder (MDD), a clinical syndrome characterized by depressed mood or loss of interest/pleasure along with other specific symptoms lasting at least 2 weeks that interfere with normal functioning.
Definition and Key Characteristics
Unipolar depression (major depressive disorder) is defined by depressed mood or anhedonia (loss of interest or pleasure in activities) plus at least 5 of the following symptoms lasting at least 2 weeks: significant weight/appetite changes, insomnia or hypersomnia, psychomotor agitation or retardation, fatigue, feelings of worthlessness or guilt, difficulty concentrating, and recurrent thoughts of death or suicide 1
The term "unipolar" distinguishes this condition from bipolar disorder, as unipolar depression involves only depressive episodes without manic or hypomanic episodes 2, 3
MDD is the most prevalent depressive disorder with an estimated lifetime prevalence of 16% in the United States, resulting in an average of 8 million ambulatory care visits per year 1
Clinical Presentation and Subtypes
Unipolar depression may present with various symptom profiles, including melancholic features (characterized by loss of pleasure in all activities, lack of reactivity to pleasurable stimuli, early morning awakening, marked psychomotor retardation or agitation, and significant anorexia or weight loss) 1, 4
In ICD-11, depressive episodes can be described according to severity (mild, moderate, or severe), remission status, and specific symptoms such as melancholic features, anxiety symptoms, panic attacks, and seasonal pattern 1
Severity of depression is typically based on symptom count, intensity, and level of functional impairment, with mild depression defined as 5-6 symptoms that are mild in severity with minimal functional impairment 1
Treatment Approaches
The American College of Physicians strongly recommends that clinicians select between either cognitive behavioral therapy (CBT) or second-generation antidepressants (SGAs) to treat patients with MDD after discussing treatment effects, adverse effect profiles, cost, accessibility, and preferences with the patient 1
Second-generation antidepressants (including selective serotonin reuptake inhibitors like fluoxetine and sertraline) are FDA-approved for treating MDD in adults 5, 6
Treatment of depression can be characterized by three phases: acute (6-12 weeks), continuation (4-9 months), and maintenance (≥1 year), with relapse defined as return of symptoms during acute or continuation phases and recurrence defined as return during maintenance 1
Distinguishing from Bipolar Depression
Misdiagnosis of bipolar depression as unipolar depression is common in both primary care and psychiatry, which can lead to inappropriate treatment with antidepressants alone 2
Factors suggesting bipolar disorder rather than unipolar depression include early-onset depression, frequent depressive episodes, family history of serious mental illness, hypomanic/manic symptoms within the depressive episode, and nonresponse to antidepressants 2, 3
Antidepressants used without mood stabilizers in bipolar depression may cause treatment-emergent hypomania/mania, rapid cycling, or increased suicidality 2
Risk Factors and Comorbidities
Depression is associated with significantly increased risk of suicide compared to the general population, with studies showing odds ratios ranging from 1.74 to 82.60 1
Treatment-resistant depression (TRD) is associated with higher rates of suicide and self-harm compared to non-TRD patients 1
Comorbid medical conditions (cardiovascular disease, hypertension, obesity) and psychiatric conditions (anxiety disorders, substance use disorders) are common in patients with mood disorders and contribute to increased mortality 2
Special Considerations
For depression secondary to medical conditions or medications, the first step should be treating the underlying medical causes and reviewing current medications that may contribute to mood symptoms 7
When selecting antidepressants for depression secondary to medical conditions, consider adverse effect profiles, potential drug interactions, prior treatment response, and patient preference 7
In cancer patients, depression prevalence is at least twice as high as in the general population, with approximately 14.3% meeting criteria for major depressive disorder 1
Remember that accurate diagnosis and appropriate treatment selection are crucial for optimizing outcomes in patients with unipolar depression, particularly in distinguishing it from bipolar depression to avoid potentially harmful treatment approaches.