Major Depressive Disorder
This patient meets diagnostic criteria for Major Depressive Disorder (MDD), not a personality disorder or persistent depressive disorder, based on the acute onset, 1-year duration, and presence of at least 5 cardinal symptoms with significant functional impairment. 1, 2
Diagnostic Reasoning
Why Major Depressive Disorder is Correct
The patient fulfills the American Psychiatric Association's criteria for MDD, which requires at least 5 symptoms present during the same 2-week period (and persisting beyond), with at least one being either depressed mood or loss of interest/pleasure 1, 3, 2:
Present symptoms in this case:
- Depressed mood ("worthless and couldn't care less") 1
- Loss of interest/pleasure (no longer gregarious, doesn't enjoy life) 1, 3
- Significant weight gain (40 pounds) 1, 3
- Hypersomnia ("feels like sleeping all day") 1, 3
- Fatigue/loss of energy (implied by hypersomnia and functional decline) 1, 3
- Feelings of worthlessness ("I'm worthless") 1, 3
- Diminished concentration ("concentration is poor") 1, 3
- Interpersonal sensitivity causing distress to others 2
Critical distinguishing features:
- Duration of 1 year with clear onset (previously gregarious and enjoyed life) indicates an episodic disorder, not a chronic/persistent condition 4, 2
- Normal physical exam and negative drug screen rule out medical causes and substance-induced mood disorder 1, 2
- Significant functional impairment ("causing distress to everyone around her") meets the requirement for clinically significant distress 1, 3
Why Other Diagnoses Are Incorrect
Persistent Depressive Disorder (Dysthymia) is excluded because it requires depressed mood on most days for at least 2 years, not 1 year 4, 5, 6. The American College of Physicians clearly states that dysthymia has a mean episode duration of 3-4 years in young adults and requires chronic symptoms for at least 2 years 4. This patient has only 1 year of symptoms 4, 5.
Borderline Personality Disorder is excluded because:
- Personality disorders represent lifelong patterns beginning in adolescence, not acute changes with clear onset 2
- The patient had a premorbid period of normal functioning ("gregarious and enjoyed life") 2
- The presentation is dominated by neurovegetative symptoms (weight gain, hypersomnia, poor concentration) rather than identity disturbance, unstable relationships, or impulsivity 3, 2
Bipolar II Disorder is excluded because there is no history of hypomanic episodes 1. The American Psychiatric Association criteria specify that symptoms must not meet criteria for a mixed episode, and there is no mention of periods of elevated mood, decreased need for sleep, increased goal-directed activity, or other hypomanic features 1.
Cyclothymia is excluded because it requires at least 2 years of numerous periods with hypomanic and depressive symptoms that do not meet full criteria for major depressive or hypomanic episodes 4. This patient has a single 1-year episode of full depressive symptoms 4.
Clinical Implications
The diagnosis of MDD in a young adult with atypical features (hypersomnia, increased appetite/weight gain, interpersonal sensitivity) suggests consideration of MDD with atypical features as a specifier, though this does not change the primary diagnosis 7, 8.
Treatment should be initiated promptly with either selective serotonin reuptake inhibitors (SSRIs) as first-line pharmacotherapy or evidence-based psychotherapy 9, 2. The FDA indicates fluoxetine is approved for treatment of major depressive disorder in both adults and adolescents 9. Treatment should continue for at least 16 to 24 weeks to prevent recurrence 2.
Suicide risk assessment is mandatory as recurrent thoughts of death or suicidal ideation are part of the diagnostic criteria and have critical safety implications 1, 3.