Electroconvulsive Therapy (ECT)

Article written and reviewed by Dr Luca Moretti

Electroconvulsive therapy, or ECT, sometimes called electroshock in everyday language, is a biological treatment for depression in which a controlled electrical stimulus, delivered under general anesthesia and after muscle relaxation, intentionally induces a generalized therapeutic seizure. Modern ECT differs greatly from historical portrayals of the procedure: it is performed in an appropriately equipped health care setting, with anesthetic monitoring, oxygen ventilation, monitoring of electroencephalographic and motor seizure activity, and serial clinical and cognitive assessment.

In major depression, ECT is one of the options with the greatest acute efficacy, especially when the episode is severe, includes psychotic or catatonic symptoms, carries high suicide risk, involves refusal of food or fluids or physical deterioration, or when multiple adequate pharmacological and psychotherapeutic treatments have not produced sufficient benefit. Its use should not, however, be reduced to a “last resort”: contemporary guidelines allow earlier use when rapidity and probability of response are clinically paramount.

Comparison with other neuromodulation techniques for depression requires distinguishing acute efficacy from cognitive tolerability, invasiveness and the need for anesthesia. rTMS, for example, does not require anesthesia and does not deliberately induce a seizure, but ECT retains a distinct clinical role in the most severe depressive presentations.

Neurobiological Rationale and Mechanisms of Action

The antidepressant effect of ECT cannot be explained by a single biochemical pathway. The therapeutic seizure transiently alters excitability in cortical and subcortical networks, functional connectivity, monoaminergic and glutamatergic transmission, neuroendocrine regulation and several processes of synaptic plasticity. Neuroimaging and biomarker studies show changes in prefrontal, limbic, hippocampal and cingulate circuits, but none of these changes alone constitutes a demonstrated causal mechanism in humans.

A central component of the procedure is the relationship among electrical dose, seizure threshold and seizure quality. Threshold varies greatly among individuals and may change over the course of treatment; stimulus prescription must therefore be individualized. Pulse intensity and waveform, electrode position and session frequency influence both efficacy and cognitive burden. The goal is not simply to obtain a “longer” seizure, but a therapeutically adequate seizure in the context of appropriately dosed stimulation and progressively assessed clinical response.

Typical autonomic responses occur during the seizure. An initial parasympathetic phase may be followed by marked sympathetic activation with transient increases in heart rate and blood pressure. This explains why preprocedural assessment should pay particular attention to unstable cardiac disease, cerebrovascular disease, conditions in which abrupt hemodynamic changes could increase risk, and interactions with anesthetics or medications that alter seizure threshold and hemodynamics.

Indications, Patient Selection and Pre ECT Assessment

The decision to use ECT is based on severity, need for rapid response, treatment history, risk profile and the patient’s informed preferences. In unipolar and bipolar depression, situations most often supporting its indication include psychotic depression, catatonia, high suicide risk, somatic compromise due to refusal of food or immobility, a previous favorable response to ECT and treatment resistant depression. A history of pharmacological treatment failures may reduce the probability of remission to some extent, but does not eliminate the possibility of a clinically meaningful response.

• High clinical priority: very severe depression with immediate threat to life, nutrition, hydration or safety; catatonia; major psychotic symptoms.
• Treatment resistance: failure to respond to adequate interventions, taking diagnosis, dose, duration, adherence and comorbidities into account.
• Previous response: a positive response to a previous ECT course is a favorable factor in shared decision making.
• Special situations: pregnancy or other conditions in which the balance between the risk of depression and pharmacological risk requires a rapid, multidisciplinary strategy.

Pre ECT assessment includes medical and psychiatric history, medication review, physical examination, anesthetic assessment and investigations targeted to individual risk. There is no universal testing panel identical for every patient: ECG, laboratory tests and further investigations are selected according to age, comorbidities and anesthetic indications. Intracranial disease, raised intracranial pressure, aneurysms or vascular malformations, recent myocardial infarction or stroke, or severe cardiovascular instability should not be managed with absolute formulas, but require specialist assessment of the risk benefit balance and, when necessary, procedural modifications or postponement.

Informed consent should cover expected efficacy, alternatives, the need for anesthesia, adverse events, possible effects on memory, the probability of relapse after response and the need for continuation treatment. In patients who lack decision making capacity, legal and procedural aspects depend on applicable law and the clinical situation; urgency and severity do not remove protective obligations.

How ECT Is Performed: Technique, Electrode Placement and Treatment Course

Each session is performed after fasting according to anesthetic instructions, with intravenous access, electrocardiographic monitoring, noninvasive blood pressure monitoring, oxygen saturation and oxygenation. After anesthesia is induced, a muscle relaxant, commonly a short acting neuromuscular blocker, is administered and ventilation is ensured. Stimulation electrodes are applied according to the selected configuration; EEG recording helps characterize the induced seizure and postictal recovery.

The most commonly used configurations are right unilateral, bitemporal and bifrontal. Right unilateral ECT, particularly with ultrabrief pulses, tends on average to reduce some cognitive effects, but requires an adequate relationship between dose and seizure threshold and is not automatically equivalent to bilateral stimulation in every situation. Bitemporal placement may be chosen when a particularly rapid response is needed or when other configurations are insufficient; the potential tradeoff is greater cognitive impact. Choice is therefore not ideological but depends on urgency, severity, response, tolerability and patient priorities.

The total number of sessions is not fixed in advance. In practice, an acute course is delivered through repeated sessions, with changes in symptoms, cognitive effects and adverse events assessed after each phase. Weekly frequency varies among health care systems and protocols. Treatment is stopped when satisfactory benefit is achieved, when response plateaus without further improvement, or when adverse effects make continuation unfavorable. Lack of an initial response may prompt reconsideration of electrode position, stimulus dose, concomitant medications and the clinical diagnosis.

Clinical Efficacy, Prognostic Factors and Relapse Prevention

Systematic reviews confirm strong acute efficacy of ECT in depression, while noting that part of the historical randomized literature is dated and that modern technique has evolved. Episodes with psychotic symptoms, older age and marked severity show high probabilities of response in numerous cohorts; by contrast, prolonged episode duration and marked pharmacological resistance are associated on average with less favorable outcomes, without excluding benefit in an individual patient.

Acute response is not equivalent to long term recovery. After a successful course, the risk of relapse is substantial, especially during the first months, if a continuation strategy is not planned. Options include antidepressant pharmacotherapy, often with augmentation strategies when indicated, or continuation ECT followed by maintenance ECT in selected patients. Continuation session frequency is progressively reduced and individualized according to clinical stability; there is no single schedule valid for everyone.

Planning should begin before the acute course is completed. Pharmacological treatment, management of relapse factors, follow up, possible psychotherapy and early signs of deterioration should be defined. In patients with recurrent episodes who have responded clearly to ECT, a maintenance strategy may be preferable to repeated delayed courses after complete relapses.

Adverse Effects, Memory, Safety and Monitoring

The most common immediate effects include headache, nausea, muscle pain, fatigue and postictal confusion. Most are transient and manageable, but duration and intensity vary with age, technique, anesthesia and individual vulnerability. Prolonged postictal delirium, significant arrhythmias, respiratory complications, dental or musculoskeletal trauma and prolonged seizures are less common and require specific clinical management.

The issue most relevant to many patients is cognition. Immediately after treatment, disorientation and temporary reduction in the ability to learn new information may occur. Objective cognitive performance generally tends to recover after the course ends, but autobiographical retrograde memory may be impaired for events close to treatment, and in some patients subjectively significant loss may persist. Standard neuropsychological measures and autobiographical experience are not perfectly aligned; monitoring should therefore not be limited to a single scale.

Cognitive risk is influenced by bilateral placement, pulse width, dose relative to seizure threshold, session frequency, total number of treatments and individual characteristics. If memory worsens to a clinically important degree, reducing frequency, modifying waveform or placement, or pausing treatment may be considered, always balancing this against the risk of leaving severe depression untreated.

Mortality directly associated with modern ECT is low, but it is incorrect to describe the procedure as risk free. Anesthesia, autonomic changes and the patient’s medical conditions determine the actual safety profile. Service quality therefore depends as much on appropriate psychiatric indication as on anesthesia, monitoring, emergency protocols, technical expertise and outcome auditing.

ECT in Special Populations and Comparison with Alternatives

During pregnancy, ECT may be considered for severe depression, psychosis or catatonia when illness risk is high or a rapid response is needed. Management should involve psychiatry, anesthesia and obstetrics, adapting maternal and fetal assessment to gestational age. In older adults, ECT is often effective, but delirium, cognitive vulnerability and cardiovascular comorbidities require careful titration and closer monitoring.

In patients with bipolar disorder, ECT may be effective for depressive episodes and some severe manic or mixed presentations, but the subsequent plan should consider prevention of future mood poles. In depression with catatonia, urgency is also determined by the risk of complications from catatonia itself, such as dehydration, thromboembolism, rhabdomyolysis and autonomic instability.

The choice among ECT, repetitive transcranial magnetic stimulation, ketamine or esketamine and other strategies is not based on an abstract ranking. ECT has a particular advantage when efficacy and speed are needed in very severe episodes; alternatives may be preferred when avoiding anesthesia is a priority, when the cognitive profile is especially important or when severity permits less intensive treatment. The best decision integrates evidence, urgency, response history and patient preferences.

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