Electroconvulsive Therapy

Electroconvulsive therapy induces a generalised, controlled seizure under general anaesthesia and muscle relaxation, using electrical stimulation applied to the scalp. It is one of the most rapidly effective and well established treatments in psychiatry.

The main indications are severe major depressive disorder (particularly with psychotic features, significant acute suicide risk, or catatonia), treatment resistant depression, and certain other severe psychiatric presentations.

Its historically negative popular image contrasts with a robust contemporary evidence base for efficacy and safety when delivered to modern standards. Understanding the indications and the adverse effect profile is essential for patient counselling and informed consent.

Mechanism and delivery

• The mechanism by which the induced seizure produces its therapeutic benefit remains incompletely understood. Proposed mechanisms include effects on neurotransmitter systems, promotion of neuroplasticity and neurogenesis (particularly within the hippocampus), and normalisation of dysregulated neuroendocrine and neuroinflammatory pathways.
• Treatment is delivered as a course of multiple sessions, commonly six to twelve, given two to three times weekly. The number is individualised according to clinical response.
• Modern treatment uses general anaesthesia with a short acting agent and a muscle relaxant, which minimise the physical manifestation of the seizure and the risk of injury.
• Electrode placement is bilateral, or unilateral over the non-dominant cerebral hemisphere, and the electrical stimulus parameters are individually titrated.
• Unilateral placement generally causes fewer cognitive adverse effects than bilateral placement, though the therapeutic response may be somewhat slower or less robust in some patients. This is a relevant consideration in treatment planning.

• The presentation prompting consideration of electroconvulsive therapy reflects the underlying psychiatric indication, most commonly severe major depressive disorder (see that condition). It is not a distinct clinical presentation in its own right.
• After successful treatment, patients often improve substantially in mood and associated depressive symptoms, frequently faster than with standard pharmacological antidepressants. This rapid onset is clinically valuable in severe, acute presentations, including significant, imminent suicide risk or severely compromised oral intake and physical health.
• Cognitive adverse effects are the most clinically significant and frequent concern. They comprise anterograde memory difficulty (affecting the formation of new memories during the course) and retrograde amnesia (affecting recall of the period immediately before treatment and, to a lesser and more variable extent, some period earlier).
• The great majority of the cognitive impact resolves over the weeks to months after the course ends. A small proportion of patients report persistent, longer term memory difficulty, particularly for autobiographical memories from around the time of treatment.
• Immediate post-procedural effects are common after each session and generally resolve within hours. They include transient headache, muscle aching (from the muscle relaxant and any residual muscular contraction), nausea, and transient post-ictal confusion.

• The decision to proceed rests on careful clinical psychiatric assessment confirming an appropriate indication, together with assessment of the patient's capacity to give informed consent. Where capacity is significantly impaired by the severity of the psychiatric condition, relevant local mental health and capacity legislation governs the treatment decision.
• Pre-treatment medical assessment is essential because general anaesthesia is required. It includes a full history and examination and baseline investigation (electrocardiography, and other testing according to medical history and risk factors), following standard pre-anaesthetic principles.
• Pay specific attention to cardiovascular history, because the induced seizure causes transient haemodynamic effects: a brief period of bradycardia followed by tachycardia and hypertension.
• Baseline cognitive assessment is recommended. It provides a reference against which treatment related cognitive change can be compared and monitored during the course.

• Established indications for electroconvulsive therapy:
  • severe major depressive disorder with psychotic features
  • severe depression with significant, acute suicide risk requiring rapid symptomatic improvement
  • depression with catatonic features or significant psychomotor retardation compromising oral intake and physical health
  • treatment resistant depression following inadequate response to an adequate trial of standard pharmacological and psychological treatment
  • certain other severe psychiatric presentations, including severe mania and catatonia of any underlying cause
• The course is typically delivered over several weeks. Therapeutic response and emerging adverse effects (particularly cognitive) are assessed regularly throughout. The number of sessions is individualised to the observed response rather than fixed in advance.
• Concurrent psychotropic medication needs careful management. Benzodiazepines have anticonvulsant properties that can interfere with adequate seizure induction, so they are generally minimised or, where feasible, temporarily withheld or reduced around sessions. Certain mood stabilisers and antidepressants may be continued or introduced as part of the integrated treatment plan.
• After an acute course, maintenance treatment is important, because the risk of relapse is substantial without it. Options are continued pharmacological maintenance or, in selected patients who relapse despite adequate pharmacological maintenance, ongoing maintenance electroconvulsive therapy at gradually extending intervals.
• Clear patient education and counselling (and family education where relevant and with consent) should cover the evidence base for efficacy and the adverse effect profile, particularly the cognitive effects.
• Explicit informed consent is required, or application of the relevant capacity and mental health legislation where capacity is significantly impaired by the underlying condition. Ideally objective cognitive monitoring continues throughout the course.
• Together these underpin safe and effective use for the established indications, where the rapid onset of action in severe, high risk presentations is most relevant.