How depression is tested on Step 1
Duration and number of symptoms define the diagnosis.
| Diagnosis | Key criteria |
|---|---|
| Major depressive disorder | ≥ 5 symptoms for ≥ 2 weeks, including low mood or anhedonia; no history of mania |
| Persistent depressive disorder (dysthymia) | Milder depressed mood most days for ≥ 2 years |
| With seasonal pattern | Episodes in fall and winter; light therapy helps |
| With peripartum onset | During pregnancy or within 4 weeks after delivery |
| Adjustment disorder | Symptoms within 3 months of a stressor, not meeting MDD criteria |
| Normal grief | Waves of sadness tied to the loss; self-esteem preserved |
Always ask about suicidal thoughts and any history of mania before starting an antidepressant.
Antidepressant classes
Mechanism predicts side effects.
| Class | Examples | Key adverse effects |
|---|---|---|
| SSRIs | Fluoxetine, sertraline, citalopram, escitalopram, paroxetine | Sexual dysfunction, GI upset, SIADH; citalopram prolongs QT |
| SNRIs | Venlafaxine, duloxetine | Raise blood pressure; duloxetine also treats neuropathic pain |
| TCAs | Amitriptyline, nortriptyline, imipramine, clomipramine | Anticholinergic, orthostasis, sedation; lethal in overdose |
| MAOIs | Phenelzine, tranylcypromine, selegiline | Hypertensive crisis with tyramine; serotonin syndrome |
| Bupropion | NE and dopamine reuptake inhibitor | Seizures; avoid in eating disorders; aids smoking cessation |
| Mirtazapine | α2 antagonist | Sedation, weight gain, increased appetite |
| Trazodone | 5-HT2 antagonist, weak reuptake inhibitor | Sedation (used for insomnia), priapism |
Antidepressants take several weeks for full effect; young people need monitoring for suicidal thinking early in treatment.
Serotonin syndrome and neuroleptic malignant syndrome
Both cause fever and altered mental status; the muscles tell them apart.
Electroconvulsive therapy and newer treatments
For severe or treatment-resistant depression.
- ECT: fastest and most effective for severe depression with psychosis, catatonia, or suicidality; safe in pregnancy. Main side effect is temporary memory loss.
- Esketamine and ketamine: NMDA antagonists with rapid effect in treatment-resistant depression.
- Psychotherapy: cognitive behavioral therapy is effective alone for mild depression and adds benefit to medication.
Worked example
Treat the most dangerous finding first.
functions Worked example — an overdose with a wide QRS
A patient who took many of their amitriptyline pills arrives drowsy, with dilated pupils, warm dry skin, and a heart rate of 125. ECG shows a QRS of 140 ms. What is the immediate treatment, and why does it work?
- Anticholinergic signs plus a wide QRS after amitriptyline indicate TCA toxicity.
- TCAs block fast sodium channels in the heart, widening the QRS and causing arrhythmias.
- Sodium bicarbonate raises serum sodium and pH, overcoming the block and reducing drug binding.
- Give IV sodium bicarbonate and monitor the ECG; manage seizures with benzodiazepines.
Answer. IV sodium bicarbonate for TCA cardiotoxicity.