Treatment-Resistant Depression

Definition & Diagnosis - Spotting Stubborn Sadness

• Treatment-Resistant Depression (TRD): Defined as Major Depressive Disorder (MDD) that fails to achieve satisfactory improvement despite ≥2 adequate trials of different antidepressant medications.
  • "Adequate trial": Sufficient dose (optimal range) for sufficient duration (typically 6-8 weeks).
  • Antidepressants should ideally be from different pharmacological classes, or include an augmentation strategy.
• Critical Diagnostic Steps:
  • Confirm the primary diagnosis of MDD (using DSM-5 or ICD-11 criteria).
  • Thoroughly rule out pseudo-resistance:
    • Inadequate antidepressant dose or duration.
    • Poor patient adherence to treatment.
    • Presence of unaddressed comorbid medical conditions (e.g., hypothyroidism, anemia) or psychiatric conditions (e.g., anxiety disorders, substance use).
    • Misdiagnosis (e.g., Bipolar depression, personality disorder).
  • Assess overall illness severity and functional impairment.

⭐ Approximately 30-40% of individuals with MDD may not respond adequately to initial standard antidepressant treatments, potentially meeting criteria for TRD.

Evaluation & Workup - Digging Deeper Doc

• 1. Confirm MDD & Severity:
  • Exclude Bipolar Disorder (e.g., MDQ).
  • Standardized scales (e.g., HAM-D, MADRS).
• 2. Review Treatment History (📌 "2 D's & A"):
  • Duration: ≥ 6-8 weeks per trial.
  • Different Classes: ≥ 2 failed adequate trials.
  • Adherence & Adequate Dose.
• 3. Screen for Confounders:
  • Medical: CBC, TSH, Vit B12/D.
  • Substance use.
  • Comorbid psychiatric conditions (anxiety, personality disorders).
• 4. Psychosocial Assessment:
  • Stressors, social support.

⭐ A key criterion for TRD is failure to respond to at least two different antidepressant trials of adequate dose and duration (typically 6-8 weeks each).

Pharmacological Strategies - Pill Power-Ups

• Optimization: Optimize current AD: Maximize dose & ensure adequate trial duration (4-6 weeks).
• Switching: Switch AD: To another agent, intra-class or different class (e.g., SSRI to SNRI/TCA).
• Augmentation Strategies:
  • Lithium: Target 0.6-1.2 mEq/L.
  • AAPs: e.g., Aripiprazole, Quetiapine XR, Olanzapine, Risperidone.
  • Thyroid Hormone (T3 - Liothyronine): 25-50 mcg/day.
  • Buspirone.
• Combination Therapy: Combine ADs: Different mechanisms (e.g., SSRI + Mirtazapine/Bupropion). ⚠️ Serotonin Syndrome.
• Novel Rapid-Acting Agents: Esketamine (intranasal)/Ketamine (IV): Rapid-acting agents for severe TRD or acute suicidal ideation.
• MAOIs (e.g., Phenelzine, Tranylcypromine): Potent, but last-line. Strict dietary (tyramine) & drug interaction precautions. ⚠️ Hypertensive Crisis.

⭐ Lithium augmentation is a gold-standard TRD strategy; response often in 2-4 weeks at therapeutic levels (0.6-1.2 mEq/L).

Non-Pharmacological Tx - Brain Boost & Banter

• Electroconvulsive Therapy (ECT)
  • Indications: Severe TRD, psychotic features, catatonia, high suicide risk.
  • Procedure: 2-3 sessions/week for 6-12 total. Bilateral or RUL (Right Unilateral) placement.
  • Key SE: Transient memory loss (anterograde > retrograde), headache.

  ⭐ ECT has the most rapid antidepressant effect; often life-saving in severe cases with acute suicidality.

• Psychotherapy ("Banter")
  • Cognitive Behavioural Therapy (CBT): Addresses negative thought patterns & maladaptive behaviours.
  • Interpersonal Psychotherapy (IPT): Focuses on relationship difficulties impacting mood.
  • Often adjunctive; improves coping, adherence & relapse prevention.
• Other Neurostimulation
  • Repetitive Transcranial Magnetic Stimulation (rTMS): Non-invasive; targets Dorsolateral Prefrontal Cortex (DLPFC). Daily sessions for 4-6 weeks. Fewer cognitive SE than ECT.
  • Vagus Nerve Stimulation (VNS): Implanted device for chronic TRD; adjunctive.
  • Deep Brain Stimulation (DBS): Investigational; for highly refractory TRD.

High‑Yield Points - ⚡ Biggest Takeaways

• TRD: Failure of ≥2 adequate antidepressant trials from different classes.
• Augmentation strategies: Lithium, atypical antipsychotics (e.g., aripiprazole, quetiapine), thyroid hormone (T3).
• Esketamine nasal spray: Rapid-acting NMDA antagonist for TRD.
• ECT: Most effective for severe TRD, especially with psychotic features or suicidality.
• rTMS: Non-invasive brain stimulation option.
• Consider VNS for chronic TRD.
• Always exclude pseudo-resistance (e.g., non-adherence, inadequate dose/duration).