PMHNP mood disorders: major depression, bipolar disorder, and psychiatric prescribing

DSM-5 MDD criteria: Five or more symptoms present for ≥2 weeks (must include depressed mood or anhedonia): depressed mood, markedly diminished interest/pleasure (anhedonia), significant weight change (≥5% in one month), insomnia or hypersomnia, psychomotor agitation or retardation (observable by others), fatigue/loss of energy, worthlessness or excessive guilt, diminished concentration, recurrent thoughts of death or suicidal ideation. Causes clinically significant distress or impairment.

Evidence-based pharmacotherapy:

• First-line: SSRIs and SNRIs. All SSRIs have comparable efficacy; choose based on side-effect profile and patient comorbidities
• Escitalopram: most selective, fewest drug interactions — preferred for older adults, patients on multiple medications
• Sertraline: broad spectrum (MDD, anxiety, OCD, PTSD, PMDD) — most versatile choice
• Fluoxetine: longest half-life (2–6 days — metabolite norfluoxetine 4–16 days) — advantageous for adherence issues, reduces discontinuation syndrome
• Venlafaxine/duloxetine (SNRIs): add norepinephrine reuptake inhibition — useful for neuropathic pain comorbidity, chronic pain
• Bupropion: dopamine/norepinephrine reuptake inhibitor — good for MDD + fatigue + hypersomnia + sexual dysfunction; lowers seizure threshold (avoid in eating disorders, seizure history, abrupt alcohol/benzodiazepine withdrawal)
• Mirtazapine: alpha-2 antagonist — sedating, appetite-stimulating — useful for insomnia + weight loss + MDD

Adequate trial: 4–6 weeks at therapeutic dose for response; 6–8 weeks for full effect. Treatment-resistant MDD: failure of ≥2 adequate antidepressant trials. Augmentation options: aripiprazole, quetiapine, lithium, buspirone, thyroid hormone. Consider esketamine (Spravato) nasal spray for treatment-resistant MDD with demonstrated lack of response to ≥2 antidepressants.

Bipolar I: At least one manic episode lasting ≥7 days (or any duration if hospitalisation required). Manic criteria: elevated/expansive/irritable mood + increased activity or energy, plus ≥3 symptoms (grandiosity, decreased sleep need, talkativeness, flight of ideas, distractibility, increased goal-directed activity, risky behaviour). Not secondary to substances or medical cause.

Bipolar II: Hypomanic episodes (≥4 days, not hospitalised, no psychotic features) plus major depressive episodes — never a full manic episode. Bipolar II is NOT "milder" than Bipolar I — depressive burden is substantial and suicide risk is high.

Mood stabilisers — PMHNP prescribing knowledge:

• Lithium: Gold standard for long-term bipolar prophylaxis. Therapeutic level: 0.8–1.2 mEq/L (acute mania), 0.6–1.0 (maintenance). Narrow therapeutic index. Toxicity >1.5: tremor, GI distress, confusion; >2.0: severe tremor, ataxia, cardiac arrhythmia, renal failure. Monitor: level, BMP (renal function, electrolytes), TSH every 6 months (causes hypothyroidism). Drug interactions: NSAIDs + thiazide diuretics significantly increase lithium levels (decrease renal clearance).
• Valproic acid (Depakote): Effective for acute mania; preferred in mixed episodes and rapid cycling. Monitor: levels (50–125 mcg/mL), LFTs, CBC, weight. Teratogenic (neural tube defects, cognitive effects) — use with caution in women of childbearing potential; require documented contraception and counselling.
• Lamotrigine: Most effective for bipolar depression prevention; weaker antimanic effect. Slow titration required to reduce risk of Stevens-Johnson syndrome (SJS) — must start at 25 mg/day and increase over 6–8 weeks. If valproate is coadministered: cut dose by 50% (valproate inhibits lamotrigine metabolism). If carbamazepine coadministered: double dose (induces metabolism).
• Atypical antipsychotics: Quetiapine, olanzapine, aripiprazole — approved for acute mania and bipolar maintenance. Risperidone and ziprasidone also used.

CRITICAL PMHNP SAFETY RULE: Antidepressants are contraindicated as monotherapy in bipolar disorder. SSRIs can precipitate manic switch, rapid cycling, and mixed states in undiagnosed or undertreated bipolar disorder. Always screen for bipolar history before initiating antidepressants.