Behavioral Health

Treatment-resistant depression: management strategies

Clinical Overview and When to Suspect Treatment-Resistant Depression

— "Adequate trial" = therapeutic dose × ≥6 weeks with documented adherence

— Some staging models (Thase-Rush, Maudsley) further grade severity by number and class of failed trials, including failed augmentation and ECT

— Outpatient with MDD on SSRI ≥6 weeks at max tolerated dose with PHQ-9 still ≥10 or minimal symptomatic change

— Patient reports "tried multiple antidepressants" — verify dose, duration, adherence before labeling TRD

— Recurrent hospitalizations for depressive episodes despite maintenance therapy

— Inadequate dose or duration (most common cause)

— Nonadherence (check pharmacy refill data, pill counts)

— Misdiagnosis: bipolar depression, MDD with psychotic features, persistent depressive disorder, PMDD

— Comorbid substance use (alcohol, cannabis, stimulants)

— Untreated medical contributors: hypothyroidism, OSA, anemia, B12 deficiency, chronic pain, steroid use

— Ongoing psychosocial stressors (IPV, financial, grief)

Step 3 management: Before escalating pharmacotherapy in a "non-responder," the first ambulatory move is to re-verify diagnosis, adherence, dose adequacy, and screen for bipolarity with the MDQ—missing a bipolar diagnosis and adding another SSRI is a classic distractor.

Board pearl: A patient labeled "treatment-resistant" who responds dramatically to a low-dose SSRI with insomnia, irritability, and racing thoughts likely has bipolar II, not TRD—switch frame to mood stabilizer + atypical antipsychotic (quetiapine, lurasidone).

Definition: Treatment-resistant depression (TRD) = failure to achieve remission after ≥2 adequate trials of antidepressants from the same or different classes during a current major depressive episode.

Epidemiology: ~30% of MDD patients meet TRD criteria; accounts for disproportionate disability, suicide risk, and healthcare cost.

When to suspect on Step 3:

Pseudo-resistance (must exclude before TRD label):

Presentation Patterns and Key History

— On Step 3, the vignette often gives a PHQ-9 score trended over visits—failure to drop ≥50% by week 6–8 signals inadequate response

— Prior trials: drug, max dose, duration, reason for stopping (side effect vs. lack of efficacy). Side-effect intolerance ≠ treatment failure

— Family history of bipolar disorder or suicide → raises suspicion for bipolar spectrum; favors mood stabilizer augmentation

— Atypical features: hypersomnia, hyperphagia, leaden paralysis, rejection sensitivity → consider MAOI historically, or bupropion/SSRI

— Melancholic features: anhedonia, early morning awakening, weight loss, psychomotor retardation → higher ECT response

— Psychotic features (delusions of guilt, nihilism): require antipsychotic + antidepressant or ECT; SSRI monotherapy is inadequate

— Seasonal pattern: consider light therapy adjunct, bupropion XL prevention

— Alcohol use disorder is the most common missed comorbidity; treat concurrently (naltrexone, acamprosate)

— Medications that depress mood: interferon, propranolol (debated), corticosteroids, isotretinoin, varenicline, hormonal contraceptives in susceptible patients

Key distinction: A patient who "felt better but stopped meds because of sexual side effects after 3 weeks" is not treatment-resistant—she had an intolerable trial, not an inadequate response. Switch to bupropion or mirtazapine, not augmentation.

Board pearl: Always recheck the MDQ or CIDI for bipolarity before declaring TRD—antidepressant-induced mania reframes the whole case.

Core MDD symptoms persisting despite treatment (SIGECAPS): sleep disturbance, anhedonia, guilt, low energy, concentration deficits, appetite change, psychomotor changes, suicidal ideation

History elements that change management:

Substance and medication review:

Psychosocial: chronic interpersonal stress, trauma history (PTSD overlap), ongoing IPV, caregiver burden, housing/food insecurity—all reduce pharmacotherapy response

Safety: every visit screen suicidal ideation, plan, intent, access to firearms (lethal means counseling)

Physical Exam Findings and Mental Status Assessment

— Bradycardia, dry skin, delayed reflex relaxation → hypothyroidism

— Tachycardia, tremor, weight loss → hyperthyroidism (can mimic anxious depression)

— Orthostatic hypotension → may limit TCA, MAOI, or trazodone titration in elderly

— Subtle parkinsonism (bradykinesia, masked facies) → consider pseudobulbar affect or early neurodegenerative disease masquerading as TRD in older adults

— Frontal release signs, executive dysfunction (clock draw, MoCA) → vascular depression or dementia—affects drug choice and prognosis

— Mood vs. affect: congruent dysphoric, restricted, blunted

— Thought content: passive death wish vs. active SI with plan/intent; ruminations, hopelessness, guilt, worthlessness

— Psychotic features: mood-congruent delusions (poverty, nihilism, somatic), auditory hallucinations of derogatory content—mandates antipsychotic + antidepressant or ECT

— Cognition: "depressive pseudodementia" improves with treatment; true dementia worsens

— Insight/judgment: poor insight predicts adherence problems

Step 3 management: In an outpatient with worsening "depression," a clock-drawing test that is abnormal in a patient over 65 should redirect workup to dementia screening and reversible cognitive contributors (B12, TSH, MRI) before escalating antidepressants—missing this is a frequent distractor.

Board pearl: The triad of anhedonia + early morning awakening + diurnal mood variation worst in AM flags melancholic depression, which has the highest ECT response rate (~80–90%).

General appearance: psychomotor retardation (slowed speech, latency), agitation (pacing, hand-wringing), poor grooming, weight changes

Vital signs: screen for medical mimics

Neurologic exam:

Mental status exam (MSE) priorities:

Suicide risk assessment: Columbia Suicide Severity Rating Scale (C-SSRS) at every visit; document ideation, intent, plan, access to means, prior attempts, protective factors

Signs of comorbid substance use: track marks, palmar erythema, spider angiomata, nasal septum changes

Diagnostic Workup — Initial Labs and Medical Mimic Screen

— TSH (± free T4): hypothyroidism is the single most common reversible mimic; treat with levothyroxine before changing psych meds

— CBC: anemia, infection

— CMP: electrolytes (hyponatremia from SSRI/SIADH especially in elderly), renal/hepatic function guiding drug selection

— Vitamin B12, folate, vitamin D: deficiencies associated with poor antidepressant response

— HbA1c, fasting glucose: uncontrolled diabetes worsens depression and vice versa

— Urine toxicology: detects covert substance use; mandatory before stimulant augmentation or ketamine

— Pregnancy test (β-hCG) in reproductive-age women before any new psychotropic

— Morning cortisol or dexamethasone suppression → Cushing if stigmata

— HIV, RPR → if risk factors or atypical presentation

— Iron studies, ferritin → fatigue-predominant

— ECG: QTc baseline before citalopram (>40 mg contraindicated, >20 mg in elderly), TCAs, ziprasidone, methadone; rule out long QT before adding QT-prolonging augmentation

— Screen OSA with STOP-BANG; untreated OSA causes refractory depression and blunts antidepressant response. Polysomnography if positive screen.

CCS pearl: On the CCS case of "depression not responding to sertraline 200 mg × 8 weeks," the highest-yield orders before changing medication are TSH, urine drug screen, PHQ-9, C-SSRS, and verify adherence—do not jump to switching agents on the first screen.

Board pearl: Hyponatremia in an elderly woman 2 weeks after starting an SSRI is SIADH—check serum sodium, hold the SSRI, and consider mirtazapine, which has lower hyponatremia risk.

Rationale: Before escalating to augmentation, ECT, or ketamine, exclude reversible medical contributors. This is a Step 3 favorite—"what test next?" in an ambulatory non-responder.

First-line outpatient panel:

Targeted additions based on history:

Sleep evaluation:

Cognitive screen: MoCA in adults ≥60 or with executive complaints

Diagnostic Workup — Advanced or Confirmatory Studies

— FDA-recognized but not routinely recommended as first-line by APA; consider after ≥2 failed trials or significant side-effect intolerance

— Identifies ultra-rapid or poor metabolizers affecting SSRIs, TCAs, atomoxetine

— Step 3 framing: useful adjunct, not a substitute for clinical judgment; insurance coverage variable

— TCA levels (nortriptyline 50–150 ng/mL, desipramine 100–300 ng/mL) when efficacy or toxicity in question

— Lithium level (target 0.6–1.0 mEq/L for augmentation; 0.8–1.2 for bipolar)

— Useful when adherence is suspect or in poor metabolizers

— Indicated for first depressive episode after age 50, focal neurologic signs, atypical course, cognitive decline, or pre-ECT workup

— White matter hyperintensities = vascular depression (Alexopoulos)—predicts SSRI resistance; address cerebrovascular risk factors

— Formal SCID-5 interview to confirm diagnosis and rule out bipolar II, PTSD, OCD, borderline PD comorbidity

— Neuropsychological testing if cognitive symptoms predominate

— ECG, CBC, BMP, pregnancy test

— Spine films or MRI if osteoporosis or prior compression fracture

— Anesthesia evaluation; medication reconciliation (hold lithium, benzodiazepines, anticonvulsants night before to lower seizure threshold appropriately)

Step 3 management: A 68-year-old with new-onset depression unresponsive to sertraline, with mild gait instability—order MRI brain before adding augmentation; vascular depression and NPH change the entire management trajectory.

Board pearl: Pharmacogenomics is adjunctive, not gatekeeping—do not delay ECT in severe suicidal melancholia waiting for genotype results.

Pharmacogenomic testing (CYP2D6, CYP2C19):

Therapeutic drug monitoring:

Neuroimaging (MRI brain):

EEG: consider if paroxysmal symptoms, possible nonconvulsive status, or pre-ECT seizure threshold concerns

Polysomnography: confirm OSA or REM sleep behavior disorder

Specialty referral / structured assessments:

Pre-ECT workup (when planning):

Pre-ketamine workup: BP (uncontrolled HTN relative contraindication), substance use history, dissociation tolerance, REMS enrollment for esketamine

Risk Stratification and Sequenced Management Logic

— Optimize: push current agent to maximum tolerated dose if partial response

— Switch: change to another agent—within class (SSRI→SSRI) or across class (SSRI→SNRI, bupropion, mirtazapine, vortioxetine)

— Combine: add a second antidepressant with complementary mechanism (e.g., SSRI + bupropion, SSRI + mirtazapine "California rocket fuel")

— Augment: add a non-antidepressant with proven efficacy (atypical antipsychotic, lithium, T3, esketamine)

— Level 1: SSRI (citalopram in trial)

— Level 2: switch or augment; remission rates fall with each subsequent level (~37%, 31%, 14%, 13%)

— Implication: earlier escalation to evidence-based augmentation/neuromodulation if no response by trial 2–3

— Mild-moderate TRD, no SI: outpatient optimization, switch, or augment; add psychotherapy (CBT, IPT, behavioral activation)

— Severe TRD with active SI, psychosis, catatonia, refusal to eat/drink, pregnancy with severe symptoms: ECT first-line

— TRD with acute suicidality: consider IV ketamine or intranasal esketamine for rapid (hours-days) effect as bridge

Step 3 management: In the outpatient with one failed adequate SSRI trial and partial response, augmentation with aripiprazole 2–5 mg or addition of bupropion is reasonable; complete non-response argues for switching class instead.

Board pearl: ECT is the most effective acute treatment for severe MDD (response ~70–90%)—reserve mental energy on exams for recognizing the indications (psychosis, catatonia, suicidality, pregnancy, prior ECT response).

Step 1 — Reconfirm diagnosis and adequacy (see chunks 1–4): adherence, dose, duration, comorbidities, substance use, bipolarity.

Step 2 — Choose between four strategies after failed first SSRI:

STAR*D-informed sequencing:

Severity-based stratification:

Psychotherapy integration: CBT or IPT improves outcomes when combined with pharmacotherapy in TRD; do not abandon therapy when escalating meds.

Neuromodulation tier: ECT > rTMS > VNS (last-line) > investigational (DBS).

Pharmacotherapy — Augmentation and Combination Strategies

— Aripiprazole 2–5 mg, titrate to 10 mg: low metabolic burden, akathisia common

— Brexpiprazole 0.5–2 mg: similar to aripiprazole, less akathisia

— Quetiapine XR 150–300 mg: sedating, weight gain, metabolic syndrome risk

— Olanzapine + fluoxetine (Symbyax): approved specifically for TRD; significant weight/metabolic effects

— Cariprazine 1.5–3 mg: newer adjunct option

— Monitor: weight, waist circumference, lipids, A1c, prolactin, EPS/AIMS every 6 months

— Target level 0.6–0.8 mEq/L; effective in 30–40%

— Especially useful with TCAs and in patients with suicidality (anti-suicide effect)

— Monitor: TSH, Cr, Ca every 6–12 months; teratogenic (Ebstein anomaly)

— 25–50 mcg/day; effective even in euthyroid patients per STAR*D level 3

— Monitor TSH, atrial fibrillation risk, osteoporosis with prolonged use

— Add 150–300 mg XL to SSRI; offsets sexual side effects and fatigue

— Avoid in seizure disorder, eating disorders

— Useful for insomnia, weight loss, anxious depression

— Watch sedation, weight gain, rare agranulocytosis

— FDA-approved for TRD as adjunct to oral antidepressant; REMS program (in-clinic monitoring 2 hrs for sedation/dissociation/BP)

— Twice weekly × 4 weeks induction, then taper

Step 3 management: For a working-age adult with TRD on sertraline 200 mg and persistent anhedonia/fatigue, add bupropion XL—addresses residual symptoms and sexual side effects simultaneously.

Board pearl: Serotonin syndrome risk rises with combinations—avoid MAOI + SSRI/SNRI (need 2-week washout, 5 weeks for fluoxetine); MAOI + linezolid, tramadol, meperidine, triptans, dextromethorphan are classic distractors.

Atypical antipsychotic augmentation (FDA-approved for TRD/MDD adjunct):

Lithium augmentation:

Thyroid (T3 / liothyronine) augmentation:

Bupropion combination:

Mirtazapine combination ("California rocket fuel" with venlafaxine):

Esketamine (Spravato) intranasal:

IV racemic ketamine: off-label, 0.5 mg/kg over 40 min, rapid antisuicidal effect

Neuromodulation and Procedural Therapies

— Indications: severe TRD, active suicidality, psychotic depression, catatonia, pregnancy with severe MDD, prior ECT response, food/fluid refusal, neuroleptic malignant syndrome

— Course: 6–12 sessions, 3×/week; bilateral (faster, more cognitive SE) vs. right unilateral (less memory impact)

— Pre-procedure: anesthesia eval, ECG, labs, dental check; hold lithium, benzos, anticonvulsants

— Adverse effects: transient anterograde/retrograde amnesia (usually resolves weeks-months), headache, myalgia, post-ictal confusion; mortality ~1/10,000 (anesthesia-related)

— Contraindications: no absolute; relative—recent MI, unstable arrhythmia, raised ICP, severe aortic stenosis, recent stroke

— Maintenance ECT prevents relapse; consider after acute response

— FDA-approved for MDD after 1 failed antidepressant trial (Step 3-relevant accessibility)

— Outpatient, no anesthesia, 30–40 min × 4–6 weeks; targets left dorsolateral prefrontal cortex

— Side effects: scalp discomfort, headache; seizure risk <0.1%

— Contraindications: ferromagnetic implants near coil, cochlear implants, seizure disorder (relative)

— Less effective than ECT but better tolerated

— FDA-approved for chronic/recurrent TRD with ≥4 failed trials; slow onset (months), surgical implant

CCS pearl: Admit the severely suicidal melancholic patient, place on suicide precautions (1:1 sitter, remove sharps/cords), consult psychiatry and anesthesia, obtain informed consent for ECT, and order pre-ECT workup—do not delay for further oral trials.

Board pearl: rTMS = best outpatient procedural option; ECT = best inpatient/severe option.

Electroconvulsive therapy (ECT):

Repetitive transcranial magnetic stimulation (rTMS):

Vagus nerve stimulation (VNS):

Deep brain stimulation (DBS): investigational (subcallosal cingulate, NAc)

Esketamine clinic (chunk 7): REMS-monitored procedural-type therapy

Psychedelic-assisted therapy (psilocybin): experimental; not yet FDA-approved for TRD

Special Populations — Elderly and Renal/Hepatic Impairment

— More medical comorbidity, polypharmacy, executive dysfunction, vascular contributions

— "Start low, go slow, but go": underdosing is a leading cause of pseudoresistance in elderly

— First-line: sertraline, escitalopram (cleaner interactions); avoid paroxetine (anticholinergic, falls), citalopram >20 mg (QTc)

— Augmentation choices: aripiprazole low-dose (2.5–5 mg) has strongest geriatric data (OPTIMUM trial); methylphenidate 5–20 mg/day for apathetic depression with medical illness

— Avoid: TCAs (anticholinergic, orthostasis, cardiac), benzodiazepines (falls, delirium)

— ECT is safe and effective in elderly—often preferred for severe melancholic or psychotic depression

— Monitor sodium (SSRI-induced SIADH), falls, bone density (SSRIs ↑fracture risk), bleeding risk on antiplatelets

— Sertraline, mirtazapine, bupropion: relatively safe; dose-adjust bupropion in eGFR <60

— Avoid lithium augmentation in CKD stage ≥3; if used, lower target, monitor closely

— Venlafaxine and duloxetine: dose reduce in CKD; duloxetine avoided in eGFR <30

— Esketamine: caution with HTN; no specific renal dose adjust but monitor

— Prefer agents with less hepatic metabolism: paroxetine, escitalopram at reduced dose

— Avoid duloxetine in chronic liver disease or significant alcohol use (hepatotoxicity)

— Bupropion: reduce dose in moderate-severe hepatic impairment

— Avoid valproate-based augmentation

— Fluoxetine, paroxetine: strong CYP2D6 inhibitors → ↑ levels of metoprolol, tamoxifen (avoid), TCAs

— Fluvoxamine: CYP1A2 inhibitor → clozapine, theophylline interactions

Step 3 management: In an 80-year-old with late-life TRD and mild cognitive impairment, augment sertraline with low-dose aripiprazole (per OPTIMUM trial) rather than switching antidepressants—better remission rates with acceptable tolerability.

Board pearl: Hyponatremia in an elderly SSRI patient → check sodium, switch to mirtazapine or bupropion.

Geriatric TRD ("late-life depression"):

Renal impairment:

Hepatic impairment:

Drug interactions in polypharmacy:

Special Populations — Pregnancy, Postpartum, and Pediatrics

— Untreated severe depression itself risks preterm birth, low birth weight, postpartum depression, suicide—do not reflexively stop antidepressants

— Preferred SSRIs: sertraline, escitalopram (lowest milk transfer postpartum, decades of data)

— Avoid paroxetine (cardiac malformations, esp. first trimester)

— Third-trimester SSRI exposure: neonatal adaptation syndrome (jitteriness, feeding difficulty, transient tachypnea) and small ↑ risk persistent pulmonary hypertension of newborn (PPHN)—do not abruptly stop

— Lithium: Ebstein anomaly risk (~1/1000–2000); fetal echo at 16–20 weeks if continued; monitor levels closely (volume of distribution changes)

— Valproate, carbamazepine: contraindicated (neural tube defects, neurodevelopmental risks)

— ECT is safe in pregnancy—often preferred for severe TRD with suicidality or psychosis; coordinate with OB and anesthesia, left lateral tilt, fetal monitoring

— Esketamine/ketamine: insufficient data, generally avoided

— Brexanolone / zuranolone: FDA-approved for postpartum depression—zuranolone is oral, 14-day course

— Confirm diagnosis and adequate trials; first-line fluoxetine (only FDA-approved for ages 8+), escitalopram for ≥12

— Black box warning: ↑ suicidal ideation in <25 years—frequent monitoring first 4 weeks, do not avoid treatment

— Combine with CBT (TADS evidence)

— Augmentation evidence is sparse; refer to child psychiatry

— ECT used selectively; rTMS FDA-cleared for adolescents 15+ with MDD

Step 3 management: A pregnant woman in third trimester on sertraline asks about stopping—continue treatment, counsel on neonatal adaptation syndrome, coordinate delivery plan; relapse risk with discontinuation outweighs neonatal risks.

Board pearl: Severe TRD in pregnancy with suicidality → ECT, not new pharmacotherapy trials.

Pregnancy:

Postpartum: screen with EPDS; sertraline first-line if breastfeeding; treat aggressively—postpartum psychosis is psychiatric emergency requiring hospitalization

Pediatrics and adolescents:

Complications and Adverse Outcomes

— Triad: mental status changes, autonomic instability (HTN, hyperthermia, tachycardia, diaphoresis), neuromuscular hyperactivity (clonus, hyperreflexia—lower extremity > upper)

— Triggers: SSRI/SNRI + MAOI, linezolid, methylene blue, tramadol, meperidine, dextromethorphan, triptans, St. John's wort

— Treat: discontinue agent, supportive care, benzodiazepines, cyproheptadine if severe

— QTc prolongation with citalopram, TCAs, ziprasidone—baseline and follow-up ECG

— TCA overdose: wide QRS, anticholinergic toxidrome, hypotension, seizures—sodium bicarbonate for QRS >100 ms

Board pearl: Highest-risk suicide window = first 30 days post-psychiatric discharge—mandates close follow-up within 7 days.

Suicide: lifetime suicide risk in MDD ~5–8%; markedly elevated in TRD. Risk factors: prior attempts, male sex, age >65 or adolescent, substance use, recent loss, access to firearms, hopelessness, command hallucinations, recent psychiatric hospitalization (first 30 days post-discharge—highest risk window)

Serotonin syndrome:

Neuroleptic malignant syndrome from antipsychotic augmentation: rigidity > clonus, fever, elevated CK, autonomic instability—dantrolene, bromocriptine, supportive

Metabolic syndrome from atypical antipsychotic augmentation: weight gain, dyslipidemia, T2DM—monitor per APA guidelines

SIADH/hyponatremia: SSRIs, SNRIs—elderly, female, low body weight, diuretics; check Na within 2–4 weeks

Bleeding risk: SSRIs inhibit platelet serotonin uptake—↑ GI bleeding (NNH ~250–500/year), especially with NSAIDs, anticoagulants; consider PPI if needed

Cardiac:

Falls/fractures: SSRIs, TCAs, mirtazapine, benzos increase falls in elderly

Sexual dysfunction: common reason for nonadherence; manage with bupropion add-on, sildenafil for men, dose reduction

Discontinuation syndrome (esp. paroxetine, venlafaxine): flu-like, dizziness, "brain zaps"—taper slowly

ECT cognitive effects: transient amnesia; right unilateral has less impact

Esketamine/ketamine: dissociation, sedation, BP spikes, abuse potential, bladder toxicity with chronic use

When to Escalate Care — ED, Inpatient, and Consultation

— Active suicidal ideation with plan/intent or recent attempt

— Homicidal ideation

— Psychotic features impairing safety or reality testing

— Catatonia (consider lorazepam challenge → ECT if refractory)

— Severe self-neglect: not eating/drinking, dehydration

— Inability to care for self due to depression severity

— Failed outpatient stabilization with worsening symptoms

— Initiating ECT (most centers)

— Voluntary preferred when capacity intact

— Involuntary criteria (state-specific): danger to self, danger to others, grave disability due to mental illness

— Document specific findings supporting hold; reassess daily

— Medical clearance: vitals, glucose, basic labs, urine tox, pregnancy, salicylate/acetaminophen levels if SI/recent ingestion

— Suicide precautions, remove belongings, 1:1 sitter

— C-SSRS documentation

— Psychiatry consultation; consider crisis stabilization unit if available

— ≥2 failed adequate antidepressant trials

— Diagnostic uncertainty (bipolarity, psychosis, personality disorder)

— Active or recent SI

— Need for ECT, rTMS, esketamine, lithium, or MAOI

— Pregnancy/postpartum with moderate-severe MDD

— Pediatric/adolescent TRD

CCS pearl: A patient presents to clinic with PHQ-9 = 22, plan to overdose, and prior attempt → immediate ED transfer with escort, do not schedule outpatient psychiatry follow-up; arrange voluntary admission, transition pharmacotherapy in coordination with inpatient team.

Step 3 management: Always schedule follow-up within 7 days of psychiatric discharge—classic Step 3 quality measure.

Inpatient psychiatric hospitalization indications:

Voluntary vs. involuntary commitment:

Emergency Department workflow:

Consultation triggers (outpatient → psychiatry):

Co-management with primary care: medication titration, monitoring labs, screening tools (PHQ-9 every visit), care coordination

Collaborative care model: evidence-based, integrates behavioral health manager + psychiatric consultant in primary care—reimbursable under CMS codes; improves remission rates

Key Differentials — Mood and Same-Category Disorders

— TRD with hyperactivation on SSRIs, family history bipolar, early onset, atypical features (hypersomnia, hyperphagia, leaden paralysis), psychotic features, postpartum onset, antidepressant-induced mania

— Use Mood Disorder Questionnaire (MDQ) or CIDI to screen

— Treatment differs fundamentally: mood stabilizer (lithium, lamotrigine, valproate) ± atypical (quetiapine, lurasidone, cariprazine, olanzapine-fluoxetine combo); antidepressant monotherapy can destabilize

— ≥2 years of chronic low-grade depression; "double depression" when MDE superimposed

— Often less response to single antidepressant trial; psychotherapy + medication superior

— Cyclic, luteal-phase symptoms; treat with continuous or luteal-phase SSRI

— Identifiable stressor, <6 months, less severe; psychotherapy first-line, brief pharmacotherapy if symptoms severe

— Alcohol, opioids, stimulant withdrawal, cannabis

— Corticosteroids, interferon, isotretinoin, varenicline, β-blockers (debated)

— Diagnosis requires resolution after substance/medication discontinuation

Key distinction: Antidepressant-induced activation, irritability, decreased need for sleep, racing thoughts, increased goal-directed activity = treatment-emergent mania → stop antidepressant, start mood stabilizer, reassess for bipolar I/II. Adding more antidepressant is wrong answer.

Board pearl: A "TRD" patient who responds robustly but briefly to each new antidepressant then relapses likely has bipolar II—pattern recognition.

Bipolar depression (most critical mimic):

Persistent depressive disorder (dysthymia):

Premenstrual dysphoric disorder (PMDD):

Adjustment disorder with depressed mood:

Cyclothymia: chronic subsyndromal hypomanic and depressive symptoms

Disruptive mood dysregulation disorder (pediatric): chronic irritability, not episodic—not bipolar

Substance/medication-induced depressive disorder:

Depressive disorder due to another medical condition: hypothyroidism, Cushing, Parkinson, stroke (post-stroke depression), HIV, pancreatic cancer, MS

Key Differentials — Other-Category Conditions Masquerading as TRD

Key distinction: Persistent fatigue + nonrestorative sleep + snoring + obesity unresponsive to escalating antidepressants → polysomnography for OSA before another medication switch.

Board pearl: Always re-screen for substance use in apparent TRD—covert alcohol or cannabis use is the most missed contributor.

Anxiety disorders (GAD, panic, social anxiety): comorbid with MDD in ~60%; persistent anxiety can blunt SSRI response—target both; consider buspirone augmentation, CBT

PTSD: trauma history with re-experiencing, avoidance, hyperarousal, negative cognitions; sertraline/paroxetine FDA-approved; prazosin for nightmares; trauma-focused CBT/EMDR essential

OCD: higher SSRI doses needed (fluoxetine 60–80 mg, sertraline 200 mg); ERP therapy; augmentation with antipsychotic

Borderline personality disorder: affective instability, identity disturbance, self-harm, dichotomous thinking—DBT is treatment of choice; pharmacotherapy is symptom-targeted, not curative; misdiagnosing BPD as TRD leads to endless medication trials

Substance use disorders: alcohol use disorder most common; "TRD" often improves with sobriety; treat concurrently

ADHD in adults: comorbid in 10–20% of MDD; fatigue, concentration deficits attributed to depression but persist after mood improves—treat with stimulants/atomoxetine; can also augment TRD in some studies (methylphenidate)

Hypothyroidism / subclinical hypothyroidism: treat with levothyroxine; T3 augmentation distinct from replacement

Obstructive sleep apnea: unrecognized OSA causes refractory fatigue, low mood, cognitive symptoms; CPAP often dramatic improvement

Vitamin deficiencies: B12, folate, vitamin D

Chronic pain syndromes (fibromyalgia, chronic low back pain): duloxetine, milnacipran address both

Neurodegenerative disease: Parkinson, Lewy body, frontotemporal dementia—apathy ≠ depression; SSRIs less effective; consider methylphenidate

Dementia with depression vs. depressive pseudodementia: treat depression first; cognitive improvement supports pseudodementia

Adrenal insufficiency, Cushing, hyperparathyroidism, pheochromocytoma (rare): atypical features warrant endocrine workup

Secondary Prevention, Maintenance, and Long-Term Plan

— First MDE: continue antidepressant at remission dose 6–12 months post-remission

— Second MDE: consider 1–3 years

— ≥3 MDEs, severe episodes, chronic depression, strong family history, residual symptoms, or TRD history: indefinite maintenance

— Same principle for augmentation agents that produced remission

— Continue effective dose (do not reduce)

— Continue psychotherapy (CBT-relapse prevention, MBCT shown to reduce relapse)

— Treat residual symptoms aggressively—residual insomnia, anhedonia, fatigue predict relapse

— Lifestyle: aerobic exercise (≥150 min/week moderate intensity—evidence-based adjunct), sleep hygiene, Mediterranean diet, social connection, light exposure

— Address modifiable risks: alcohol cessation, OSA treatment, thyroid optimization

— Lithium reduces suicide in unipolar and bipolar depression

— Clozapine reduces suicide in schizophrenia (not MDD but recognize on exams)

— Means restriction counseling—lethal means counseling about firearms is high-yield Step 3

— Safety planning intervention (Stanley-Brown model)

Step 3 management: A patient on third MDE achieving remission on sertraline + aripiprazole → continue both indefinitely at remission doses, reinforce CBT, exercise prescription, and lethal means counseling.

Board pearl: Mindfulness-based cognitive therapy (MBCT) reduces relapse in recurrent MDD by ~30%.

Maintenance duration after acute remission:

Maintenance ECT or rTMS: for patients who responded acutely and have history of frequent relapse; taper frequency (weekly → biweekly → monthly)

Maintenance esketamine: weekly or biweekly dosing post-induction, individualized

Relapse prevention strategies:

Suicide-specific prevention:

Tapering antidepressants when appropriate: ≥4 weeks gradual taper, slower for paroxetine, venlafaxine; counsel on discontinuation symptoms and relapse signs

Patient self-monitoring: PHQ-9 self-administration, mood tracking apps

Health system tools: measurement-based care (PHQ-9 at every visit), collaborative care model

Follow-Up, Monitoring Parameters, and Counseling

— Acute phase: every 1–2 weeks during titration and first month

— Continuation phase: monthly until stable remission

— Maintenance: every 3 months, then 6 months if stable

— Post-psychiatric hospitalization: within 7 days (quality measure)

— PHQ-9 every visit—target remission (<5), not just response

— GAD-7 if anxiety comorbidity

— C-SSRS at every visit for suicidality

— Documented dose, duration, adherence

— SSRIs/SNRIs: sodium at 2–4 weeks (elderly), BP for venlafaxine, weight

— TCAs: ECG at baseline and titration, drug levels, anticholinergic burden

— Lithium: level every 5 days during titration then q3–6 months; TSH, Cr, Ca q6–12 months

— Atypical antipsychotics: weight/BMI, waist, BP every visit; fasting glucose/lipids at baseline, 3 months, then annually; AIMS q6 months for tardive dyskinesia

— Bupropion: BP, seizure precautions

— Esketamine: BP pre/post-dose, sedation, dissociation monitoring 2 hours in REMS clinic

— ECT: cognitive monitoring (MoCA serial), retitration if cognitive decline

— Expect 2–6 weeks for full effect; nausea, headache, jitters often improve in 1–2 weeks

— Sexual dysfunction—proactive discussion

— Discontinuation symptoms if missed doses

— Bleeding risk if on NSAIDs/anticoagulants

— Suicidality monitoring first 4 weeks especially <25 years (FDA black box)

Step 3 management: Post-discharge follow-up within 7 days, PHQ-9 at every visit, document C-SSRS, reinforce safety plan—these are the Step 3 quality benchmarks.

Board pearl: Remission, not response, is the goal—residual symptoms predict relapse and chronic course.

Visit cadence:

Measurement-based care (Step 3 favorite):

Medication-specific monitoring:

Side-effect counseling at initiation:

Lifestyle prescription: structured exercise, sleep hygiene, alcohol reduction, social activation, light exposure

Psychotherapy referral: CBT, IPT, behavioral activation, MBCT—reimbursable, augments medication outcomes

Ethical, Legal, and Patient Safety Considerations

— Required from patient (or surrogate if incapacitated)—explain procedure, anesthesia, cognitive side effects (anterograde > retrograde amnesia), alternatives, no-treatment risks

— Capacity assessment: understanding, appreciation, reasoning, expression of choice

— If patient lacks capacity due to severe depression with delusions or catatonia, surrogate decision-maker per state law; court order may be needed

— Reassess capacity if mental state changes

— State-specific criteria; document danger to self/others or grave disability due to mental illness

— Least restrictive alternative principle—voluntary first if capacity allows

— Patient retains right to refuse most treatments even when committed (in many states), except in emergency

— Duty to warn/protect identifiable third parties when patient makes credible threat (state-dependent)

— Document risk assessment, clinical reasoning, protective actions

— Limit dispensing quantity in actively suicidal patients (avoid TCA prescriptions—lethal in overdose)

— Lethal means counseling: firearm safe storage or temporary removal—evidence-based intervention reducing suicide deaths

— Highest-risk window post-psychiatric discharge—mandates 7-day follow-up, warm handoff, medication reconciliation, safety plan

— Bridge prescriptions to avoid lapses

Step 3 management: A severely depressed patient with delusional guilt refuses ECT—assess decisional capacity; if incapacitated, engage surrogate and/or pursue court order; do not simply accept refusal without capacity evaluation.

Board pearl: Firearm lethal-means counseling reduces suicide mortality and is standard of care in TRD with SI.

Informed consent for ECT:

Involuntary hospitalization:

Right to refuse vs. emergency treatment: psychiatric medications generally cannot be forced without due process; emergencies (imminent danger) allow short-term intervention

Confidentiality and Tarasoff duty:

Mandatory reporting: child/elder abuse, IPV in some states; impaired drivers in some jurisdictions

Pharmacotherapy safety:

Transitions of care risk:

Pharmacogenomic and ketamine clinics: disclose off-label use, evidence limitations, cost (often out-of-pocket), abuse potential of ketamine

Adolescent confidentiality: balance autonomy with parental involvement; mandatory parental notification for imminent risk

Professional boundaries: dual relationships, gifts, social media

High-Yield Associations and Rapid-Fire Clinical Facts

Board pearl: When in doubt on Step 3, choose measurement-based care + 7-day post-discharge follow-up + lethal means counseling—these are health-system answers favored by question writers.

TRD definition: failure of ≥2 adequate antidepressant trials (≥6 weeks, therapeutic dose)

STAR*D remission rates: 37% → 31% → 14% → 13% across levels—earlier escalation pays off

OPTIMUM trial: aripiprazole augmentation > switching to bupropion in older adults with TRD

ECT response rate: 70–90% in melancholic/psychotic depression—highest of any modality

Esketamine (Spravato): FDA-approved for TRD (2019), TRD with acute suicidality (2020); REMS program

rTMS: FDA-approved after 1 failed trial; outpatient; left DLPFC target

Olanzapine-fluoxetine combination (Symbyax): first FDA-approved combo for TRD

Lithium: anti-suicide effect independent of mood-stabilizing effect; target 0.6–0.8 mEq/L for augmentation

T3 (liothyronine): 25–50 mcg/day augmentation, effective in euthyroid TRD

Sertraline + bupropion: classic outpatient combination addressing residual fatigue, sexual side effects

MAOI washout: 2 weeks (5 weeks for fluoxetine)

Discontinuation syndrome: paroxetine, venlafaxine highest risk; fluoxetine lowest (long half-life)

Citalopram QTc: max 40 mg adults, 20 mg elderly/CYP2C19 PM

Paroxetine: avoid in pregnancy (cardiac), elderly (anticholinergic), and patients on tamoxifen (CYP2D6)

Bupropion: contraindicated in seizure disorder, eating disorders, abrupt alcohol/benzo withdrawal

Mirtazapine: weight gain, sedation, ↓ nausea, ↓ sexual side effects; lower hyponatremia

Vortioxetine: multimodal serotonergic; less sexual dysfunction; cognitive symptom benefit

Brexanolone/zuranolone: postpartum depression

Vascular depression (Alexopoulos): late-life, executive dysfunction, white matter lesions, poor SSRI response

Suicide risk windows: first month post-hospital discharge, first 4 weeks on new antidepressant <25 years

Highest-yield missed comorbidity: alcohol use disorder

Highest-yield missed diagnosis: bipolar II

Mindfulness-based cognitive therapy: reduces recurrent MDD relapse ~30%

Collaborative care model: evidence-based primary care integration; reimbursable CMS codes

Board Question Stem Patterns

Step 3 management: When the stem includes outpatient PHQ-9 trending, the right answer is almost always measurement-based escalation: optimize → augment → switch → neuromodulation, in that order, integrated with psychotherapy.

Pattern 1 — "Tried 3 SSRIs, still depressed": check dose, duration, adherence, bipolar screen, substance use, thyroid before escalating. Answer often "verify adherence" or "obtain MDQ" rather than "switch medication."

Pattern 2 — Antidepressant-induced activation: young adult on SSRI develops decreased sleep, racing thoughts, increased energy → stop antidepressant, evaluate for bipolar, start mood stabilizer or atypical (lurasidone, quetiapine).

Pattern 3 — Elderly with melancholic, psychotic, or suicidal depression refractory to meds: answer = ECT.

Pattern 4 — Pregnant patient with severe TRD and SI: answer = ECT (safe in pregnancy).

Pattern 5 — Outpatient with PHQ-9 = 18 on sertraline 200 mg × 8 weeks, partial response: answer = augment with aripiprazole or add bupropion, not switch.

Pattern 6 — Hyponatremia 2 weeks after SSRI in elderly: stop SSRI, switch to mirtazapine or bupropion.

Pattern 7 — TCA overdose with wide QRS: sodium bicarbonate IV.

Pattern 8 — Serotonin syndrome: stop offending agent, supportive care, cyproheptadine if severe; recognize clonus, hyperreflexia (LE>UE), autonomic instability.

Pattern 9 — Patient with PTSD labeled "TRD": answer = trauma-focused therapy (CBT-PTSD, EMDR) + sertraline/paroxetine; prazosin for nightmares.

Pattern 10 — Adolescent on SSRI develops SI: continue medication, increase monitoring; do not stop abruptly (FDA black box requires monitoring, not avoidance).

Pattern 11 — Patient discharged after suicide attempt: schedule follow-up within 7 days, safety plan, lethal means counseling, limited medication quantity.

Pattern 12 — Refractory depression + fatigue + snoring + obese: polysomnography for OSA before another med change.

Pattern 13 — Acute suicidal TRD requiring rapid effect: IV ketamine or intranasal esketamine as bridge.

Pattern 14 — Postpartum severe depression: brexanolone or zuranolone (oral, 14 days).

Pattern 15 — Patient refuses ECT but lacks capacity from psychotic depression: assess capacity formally → surrogate decision-maker / court order.

One-Line Recap

Treatment-resistant depression is failure to remit after ≥2 adequate antidepressant trials, and its management hinges on confirming the diagnosis and treatment adequacy, then sequencing evidence-based strategies—optimize, switch, combine, augment with atypical antipsychotics or lithium, and escalate to neuromodulation (rTMS, ECT) or esketamine—while integrating psychotherapy, treating comorbidities, and embedding measurement-based care, safety planning, and close follow-up across transitions.

Board pearl: On Step 3, the right answer to "what next?" in apparent TRD is rarely "another SSRI"—it is reassess diagnosis, optimize what's working, then escalate with intent, always pairing pharmacotherapy with psychotherapy and structured follow-up.

Rule out pseudoresistance first: verify dose, duration, adherence; screen for bipolar (MDQ), substance use, thyroid disease, OSA, vascular depression.

Augmentation hierarchy: aripiprazole/brexpiprazole/quetiapine XR > lithium > T3; add bupropion or mirtazapine to SSRI for combination; reserve esketamine for true TRD with rapid-effect need.

Neuromodulation: ECT for severe/psychotic/suicidal/pregnant/catatonic; rTMS for outpatient after 1 failed trial; both have strong evidence and underutilization on exam stems.

Safety and systems: 7-day post-discharge follow-up, lethal means counseling, PHQ-9 and C-SSRS every visit, collaborative care model, indefinite maintenance after ≥3 episodes—these are the highest-yield Step 3 answers when in doubt.