Missed bipolar II, antidepressant monotherapy, and polarity-safe rebuild (MEQ)

(i) Formulation and misdiagnosis pathway. Working diagnosis: bipolar II disorder, current episode depressed. Operational basis: recurrent major depression plus clear hypomanic periods (≥4 consecutive days of elevated energy with decreased sleep need, pressure, spending, libido increase), observable change, no hospitalisation and no psychosis (so not mania / bipolar I). Misdiagnosis pathway is classic: depression-first onset, patient values hypomania as wellness, no collateral early, unipolar antidepressant stacking without polarity screen. Cyclothymia is excluded because full major depression and full hypomania criteria are met. Borderline PD not established by this stem alone; tempo is days not minutes.[4][5]

(ii) Acute risk priorities. Structured suicide assessment (intent beyond passive wishes, plan, means, protective factors), alcohol/substance, mixed features screen (depression plus energy), supports, capacity. Same-day senior review if risk escalates; lower threshold for admission if means or intent emerge. Means restriction and safety planning with partner involvement (consent-aware). Do not minimise because the elevated pole was 'only hypomania.'[4]

(iii) Medication rebuild. Obtain baselines (FBC, U&E/eGFR, calcium, TFT, LFT, glucose/lipids, weight/BP, pregnancy test if relevant, ECG if indicated) before lithium/SGA. Plan supervised taper of dual antidepressant load (venlafaxine and mirtazapine) rather than abrupt poly-stop if discontinuation risk is high — but do not leave her on dual AD monotherapy logic. Start polarity-safe cover, e.g. quetiapine titrated toward 300 mg oral at night (BOLDER bipolar I/II depression evidence) with metabolic monitoring, and/or lithium often starting 450–900 mg/day with 12-hour trough plan about 0.6–0.8 mmol/L for maintenance-range depression care (individualise). STEP-BD: adjunctive antidepressants did not beat mood stabiliser plus placebo for durable recovery — dual AD without stabiliser is indefensible.[1][2][4]

(iv) 12-month plan and lamotrigine. After acute stabilisation, consider lamotrigine for depression-prevention: slow adult titration (e.g. 25 mg daily weeks 1–2, 50 mg weeks 3–4, then stepwise toward commonly used 100–200 mg/day targets), counsel rash and stop rules, restart low if interrupted more than about 5 days. Maintenance evidence for lamotrigine is strongest as prevention after slow build, not as a 72-hour rescue drug.[3][4] Psychoeducation, IPSRT/CBT-bipolar, sleep regularity, mood chart with partner, substance review, crisis plan, metabolic and lithium monitoring schedule, occupational recovery goals. Review diagnosis education so she no longer labels hypomania as 'being well.'[4]