Mood Disorders
Core concepts
Differentiate major depressive disorder, persistent depressive disorder, bipolar I (mania), bipolar II (hypomania + depression), cyclothymia, and substance/medical-induced mood disorders. Mania requires ≥1 week (or hospitalisation) of elevated/irritable mood plus increased energy; hypomania requires ≥4 days without marked impairment or psychosis. Mixed features and rapid cycling affect treatment choice.
Treatment
- Bipolar depression: avoid antidepressant monotherapy; use lithium, lamotrigine, or quetiapine.
- Acute mania: antipsychotics ± lithium/valproate; consider ECT if severe.
- Unipolar depression: SSRIs first-line; ECT for severe, psychotic, or catatonic depression and for life-threatening refusal of food/fluid.
- Lithium: monitor levels (0.6–0.8 mmol/L maintenance), renal and thyroid function; toxicity risk with NSAIDs, thiazides, dehydration.
Traps
- Missing a past hypomanic episode in a patient presenting with depression - always screen for bipolarity.
- Starting an antidepressant in bipolar disorder and precipitating mania or rapid cycling.
- Forgetting serotonin syndrome (clonus, hyperreflexia, agitation) versus NMS.
- Overlooking postpartum and seasonal patterns.
Worked example
A patient with recurrent depression, two prior episodes of 3-day elevated mood with decreased sleep and increased goal-directed activity, has bipolar II, not unipolar depression - and should be started on a mood stabiliser.