Learning Objective
By the end of this session, medical students should be able to differentiate major mood disorders, recognize their characteristic features, and identify associated psychotic symptoms relevant to USMLE Step 1 clinical vignettes.
Definition
Mood disorders are psychiatric conditions characterized by abnormal fluctuations in emotional states, often resulting in distress and impaired social or occupational functioning. They can present with episodic superimposed psychotic features (delusions, hallucinations, disorganized speech/behavior) during mood episodes.
Classification of Mood Disorders
| Disorder | Key Features | Episodes Required | Psychotic Features | Notes |
|---|---|---|---|---|
| Major Depressive Disorder (MDD) | Depressed mood, anhedonia, fatigue | ≥1 major depressive episode (MDE) | May occur during MDE | No manic/hypomanic episodes |
| Persistent Depressive Disorder (Dysthymia) | Chronic low mood | ≥2 years | Rare | Mild but persistent |
| Bipolar I Disorder | Mania ± depression | ≥1 manic episode | May occur in mania or depression | Severe, may require hospitalization |
| Bipolar II Disorder | Hypomania + MDE | ≥1 hypomanic + ≥1 MDE | Only during MDE | No full mania |
| Cyclothymic Disorder | Fluctuating hypomanic and depressive symptoms | ≥2 years | Usually absent | Subthreshold mood symptoms |
| Schizoaffective Disorder | Mood episode + psychosis | Mood episodes + ≥2 weeks of psychosis without mood | Always | Psychosis must persist outside mood episodes |
Mood Episodes
| Episode Type | Description |
|---|---|
| Mania | Abnormally elevated, expansive, or irritable mood, often with increased energy, decreased need for sleep, grandiosity, pressured speech, and risky behavior |
| Hypomania | Milder form of mania; does not cause severe functional impairment or hospitalization |
| Major Depressive Episode (MDE) | Depressed mood or anhedonia with ≥5 symptoms, including fatigue, sleep/appetite disturbance, worthlessness, or suicidal ideation |
| Euthymia | Normal, stable mood between episodes |
Key Points
- Psychotic features may appear during mania or depression, but in schizoaffective disorder, psychosis occurs independently of mood episodes.
- Bipolar I requires at least one manic episode; Bipolar II requires at least one hypomanic episode and one MDE.
- Differentiation from schizophrenia hinges on the timing of psychotic symptoms relative to mood episodes.
- Chronic mild mood fluctuations are characteristic of dysthymia and cyclothymic disorder.
