Major Depressive Disorder vs Bipolar I Disorder
Major Depressive Disorder and Bipolar I Disorder are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Major Depressive Disorder vs Bipolar I Disorder at a glance
- Major Depressive Disorder: Persistent depressed mood or anhedonia >=2 weeks with neurovegetative and cognitive symptoms causing functional impairment.
- Bipolar I Disorder: At least one lifetime manic episode; depressive and hypomanic episodes common but not required for diagnosis.
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Side-by-side comparison
| Feature | Major Depressive Disorder | Bipolar I Disorder |
|---|---|---|
| At a glance | Persistent depressed mood or anhedonia >=2 weeks with neurovegetative and cognitive symptoms causing functional impairment. | At least one lifetime manic episode; depressive and hypomanic episodes common but not required for diagnosis. |
| Classic presentation | SIG E CAPS mnemonic — Sleep, Interest, Guilt, Energy, Concentration, Appetite, Psychomotor, Suicidality. Five of nine including depressed mood or anhedonia x 2 weeks.; Depressed mood most of the day, nearly every day (self-reported or observed); Markedly diminished interest or pleasure in nearly all activities (anhedonia); Significant… | Manic patient with reduced need for sleep (e.g., sleeping 2-3 hours and feeling rested), spending sprees, hypersexuality, and grandiose business plans.; Manic episode: elevated, expansive, or irritable mood >=1 week with increased energy/activity; DIG FAST: Distractibility, Indiscretion (risky behaviors), Grandiosity, Flight of ideas,… |
| Workup / key labs | DSM-5-TR: >=5 of 9 symptoms present for >=2 weeks, with at least one being depressed mood OR anhedonia. Symptoms must cause clinically significant distress/impairment, not be attributable to a substance or medical condition, and not be better explained by a psychotic or bipolar disorder. PHQ-9 >=10 supports diagnosis and tracks severity… | DSM-5-TR Bipolar I: At least one lifetime manic episode — distinct period (>=7 days, or any duration if hospitalized) of elevated/expansive/irritable mood AND increased goal-directed activity/energy, with >=3 DIG FAST symptoms (>=4 if mood is only irritable), causing marked impairment or psychotic features. The episode is not… |
| Imaging | Neuroimaging not routine; consider MRI brain if new focal neurologic findings, atypical features, or first episode after age 50 | Neuroimaging not routine; consider MRI if atypical features or first episode after age 50 |
| First-line treatment | Psychotherapy — cognitive behavioral therapy (CBT) or interpersonal therapy (IPT); comparable to medication for mild-moderate episodes; SSRI — sertraline, escitalopram, fluoxetine (first-line pharmacotherapy; start low, titrate after 2-4 weeks; full effect at 6-8 weeks); SNRI — venlafaxine, duloxetine, desvenlafaxine (consider with… | Mood stabilizer — lithium (gold standard, anti-suicide effect), valproate, or lamotrigine (bipolar depression and maintenance); Atypical antipsychotic — quetiapine, olanzapine, risperidone, aripiprazole, lurasidone, cariprazine; Acute mania: lithium OR valproate + atypical antipsychotic; add benzodiazepine for agitation; Bipolar… |
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