Electroconvulsive Therapy (ECT)

History

Mechanism of Action

• Neurotransmitter effects: ECT affects serotonin, norepinephrine, and dopamine - receptors are downregulated similarly to the effects of antidepressant medications. Serotonin is especially enhanced in the hypothalamus and brainstem.
• Neuroendocrine effects: ECT releases a broad range of neuroendocrine factors including ACTH, cortisol, prolactin, and endorphins from the pituitary. Especially with bilateral ECT, prolactin levels rise sharply after seizure activity - this is used as a peripheral indicator that a bilateral generalized seizure has occurred.
• Neuroplasticity: Animal models and recent systematic reviews (PMID 38981574) show ECT shares neuroplasticity effects with ketamine, including BDNF upregulation and synaptogenesis, particularly in the hippocampus and prefrontal cortex.
• Electrophysiology: ECT induces a generalized synchronized neuronal discharge. Regular brain activity is desynchronized; a seizure occurs when a large percentage of neurons fire in unison, propagating across the cortex into deeper structures and eventually encompassing the whole brain in high-voltage synchronous firing.

Indications

• Life-threatening depression (severe suicidal ideation, refusal to eat/drink, inanition)
• Catatonia (responds to as few as 1-4 treatments)
• Severe mania with life-threatening behavior
• Neuroleptic malignant syndrome

• Major depressive disorder unresponsive to adequate pharmacotherapy (typically 2+ drug trials)
• Bipolar depression
• Schizoaffective disorder
• Schizophrenia with prominent affective symptoms

• Preferred over pharmacotherapy in some cases of depression in pregnancy (safer than many drugs)
• Elderly patients with severe depression who cannot tolerate antidepressant side effects
• Patients with Parkinson's disease and severe depression (also improves motor symptoms transiently)

• Space-occupying intracranial lesions or elevated intracranial pressure (risk of brain herniation during the hemodynamic surge of seizure)
• Recent myocardial infarction or unstable angina
• Pheochromocytoma
• High anesthetic risk (ASA Class IV-V)

Pre-ECT Evaluation

• Complete blood count (CBC), serum electrolytes, urinalysis, liver function tests
• ECG (cardiac evaluation, especially in older patients)
• Medical history and physical examination
• Anesthesia consultation
• Spinal X-ray series is no longer routinely indicated given modern muscle relaxation techniques
• Cognitive baseline assessment (memory testing)

Electrode Placement

• Right unilateral ECT at 6x seizure threshold is roughly equivalent in efficacy to bilateral ECT but with fewer cognitive side effects.
• Ultra-brief pulse widths with bilateral ECT are likely to be ineffective.

Procedure and Anesthesia

1. NPO (nothing by mouth) for 8 hours before treatment
2. Glycopyrrolate or atropine (anticholinergic) to reduce oral secretions and attenuate the vagal bradycardia during seizure induction
3. General anesthesia: methohexital (barbiturate of choice; shorter-acting than thiopental, leading to less post-ictal confusion) or propofol
4. Succinylcholine (0.5-1 mg/kg IV): depolarizing neuromuscular blocker to prevent tonic-clonic movements and musculoskeletal injury. The "cuff technique" - an inflated cuff on one ankle before succinylcholine prevents paralysis of that limb, allowing visual confirmation of seizure activity
5. Oxygenation: 100% O2 via mask before and after stimulus
6. Stimulus delivery: Brief-pulse or ultra-brief-pulse square-wave current. Charge is measured in milliampere-seconds (mC). Only ~20% of applied charge penetrates the skull to reach neurons (skull has high impedance; brain has low impedance)
7. Seizure monitoring: Tonic phase (10-20 seconds of plantar extension) followed by clonic phase (rhythmic contractions). EEG monitoring confirms generalized seizure. Minimum effective seizure duration: 25 seconds

Dosing and Seizure Threshold

• The seizure threshold varies up to 40-fold between individuals and must be empirically determined with a titration method at the first treatment
• Bilateral ECT is typically given at 1.5x seizure threshold; right unilateral ECT requires 6x seizure threshold for comparable efficacy
• If no seizure is induced: check electrode contact, increase stimulus intensity by 25-100%, consider caffeine sodium benzoate (500-2,000 mg IV, 5-10 min before) to lower seizure threshold, or change the anesthetic agent

Treatment Course

• Frequency: 2-3 times per week (twice-weekly causes less memory impairment than three times per week)
• Stop when maximal improvement is reached - defined as no further improvement after two consecutive treatments
• If not improving after 6-10 sessions, switch to bilateral placement at 3x seizure threshold before abandoning ECT

Maintenance ECT

• Continuation pharmacotherapy: antidepressant + lithium (nortriptyline + lithium has RCT evidence)
• Continuation ECT: weekly then tapering to monthly, for 6 months
• Maintenance ECT: ongoing monthly treatments for chronic relapsing patients

Adverse Effects

Cognitive (most clinically significant)

• Acute confusional state (post-ictal): disorientation lasting minutes to hours after each treatment; largely benign
• Anterograde amnesia: difficulty forming new memories during treatment course; typically resolves within days to weeks
• Retrograde amnesia: loss of memories for events surrounding treatment; can extend back months to years. Usually resolves, but may be permanent for some events close to the treatment period
• Bilateral > right unilateral placement for cognitive effects
• Ultra-brief pulse width reduces cognitive side effects vs standard brief pulse

Cardiovascular

• Bradycardia / asystole: brief, mediated by parasympathetic activation (vagal) at seizure onset - prevented by anticholinergic premedication
• Tachycardia and hypertension: sympathetic surge during and immediately after seizure; can be treated with short-acting beta-blockers (esmolol) or nitroprusside

Other

• Headache: common post-treatment; managed with analgesics
• Myalgia: from succinylcholine fasciculations
• Nausea: from anesthesia
• Prolonged seizures (>180 seconds) / status epilepticus: terminate with IV diazepam 5-10 mg or additional barbiturate + intubation
• Tardive seizures: additional seizures appearing later in patients with preexisting seizure disorders; rare de novo epilepsy

Mortality

• Approximately 1 death per 10,000 patients (comparable to anesthesia risk for minor surgical procedures). The most serious risk is cardiovascular.

Efficacy

• ECT is the most effective treatment for major depression, with response rates of 70-90% in drug-resistant patients, significantly higher than any pharmacological agent
• Onset of response is rapid (often 1-2 weeks), making it valuable in life-threatening presentations
• Effective even in psychotic depression, melancholic depression, and late-life depression
• A 2026 meta-analysis (PMID 41206419) confirms ultrabrief pulse ECT is effective for depression with a favorable cognitive profile

Special Considerations

• Pregnancy: ECT is generally preferred over antidepressants in the first trimester for severe depression. Precautions include uterine monitoring, pelvic tilt, intubation (aspiration risk), and obstetric standby
• Elderly: ECT is well-tolerated and often preferred; longer post-ictal confusion is common
• Parkinson's disease: ECT transiently improves both mood and motor symptoms
• Clozapine + ECT: can be combined safely in treatment-resistant schizophrenia (covered in The Clozapine Handbook); synergistic response reported
• Stimulation with ECT for dementia: A 2024 systematic review (PMID 37170574) supports ECT use in dementia patients with severe behavioral symptoms, with careful monitoring