Cardiazol-induced seizures as a treatment for schizophrenia

Schizophrenia and epilepsy were treated as biologically antagonistic disorders, so chemically inducing epileptiform seizures with Cardiazol (pentylenetetrazol/Metrazol) was expected to produce remission in schizophrenia.

1 episode

Current understanding

Schizophrenia and epilepsy are not biologically opposing disease states whose coexistence can be therapeutically reversed by provoking seizures. Early Cardiazol results were distorted by uncontrolled comparisons, changing diagnostic definitions and outcome measures that sometimes equated quieter or more manageable behavior with recovery. Convulsive treatment itself should not be dismissed wholesale: modern electroconvulsive therapy has evidence-based indications, including severe depression, catatonia and selected treatment-resistant conditions. The historical error was the specific antagonism theory and the resulting use of an intensely distressing, poorly controlled chemical convulsant as a routine schizophrenia treatment.

Consequences and human impact

Cardiazol therapy spread through British public mental hospitals within roughly two years of its introduction. Patients received intravenous convulsant injections that could produce overwhelming pre-seizure terror and violent generalized convulsions. The Board of Control investigated and reported on the method as hospitals adopted it, but the original theory that induced epilepsy would counteract schizophrenia collapsed quickly.

How the consequences followed

Cardiazol is also known as pentylenetetrazol or Metrazol. Chemical Cardiazol convulsions for schizophrenia are distinct from modern ECT. ECT replaced Cardiazol partly because an electrical stimulus allowed a more controllable seizure with less pre-convulsive terror and fewer traumatic injuries.

Some later evidence suggested convulsive treatment could benefit affective illness. That does not rescue Meduna's original claim that schizophrenia could be treated because epilepsy and schizophrenia were biologically antagonistic.

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British institutions using shock treatments in the 1938 Board of Control survey were using Cardiazol

1938

Board of Control issued a national report on Cardiazol treatment in schizophrenia

1941

British clinicians were acknowledging that the original schizophrenia indication had been abandoned

Quantitative figures are highlighted only when the cited evidence supports them. The scale of a related catastrophe is not automatically treated as a death toll caused solely by this belief.

Institutional episode

England and Wales

1937–1941Policy basis

Britain rapidly adopted Cardiazol convulsive therapy after its 1937 introduction. The treatment was built on the theory that schizophrenia and epilepsy were biological opposites, so provoking epileptiform seizures should drive schizophrenia into remission. The Board of Control investigated the method and by late 1938 found Cardiazol in use at 89 institutions. Subsequent experience exposed unstable remission claims, serious distress and injuries, and major problems in how “improvement” was measured. By 1941 British clinicians were explicitly saying that the original conception of convulsive therapy as a schizophrenia treatment had been abandoned, while ECT replaced the less controllable chemical procedure.

Institutions

Board of Control for England and Wales
British public mental hospitals
Royal Medico-Psychological Association

Documented consequences

Large-scale chemical induction of generalized seizures in psychiatric patients
Extreme anticipatory fear and distress immediately before convulsions
Risk of vertebral and other fractures, memory disturbance and cerebral injury
Behavioral quieting or ward manageability could be misclassified as therapeutic improvement
Rapid national diffusion before the underlying schizophrenia theory had been established

Institutional machinery

Cardiazol convulsive treatment reached Britain in 1937 and spread extremely rapidly through the public mental-hospital system. The Board of Control noted its use at several institutions in its 1937 report, sent officials to Hungary to study the method and published a dedicated 1938 report on Cardiazol and shock treatment in schizophrenia. A late-1938 Board survey found shock treatments underway at 92 institutions, 89 of them using Cardiazol. The therapy was originally justified by Ladislas Meduna's hypothesis that epilepsy and schizophrenia were biologically antagonistic and that inducing epileptiform seizures could therefore cause schizophrenic remission. By 1941 British clinicians were acknowledging that this original conception had been abandoned, while electrical convulsive therapy was rapidly supplanting the chemical method.

Sources and what they establish

“A violent thunderstorm”: Cardiazol treatment in British mental hospitalsHistory of Psychiatry / PubMed
Report on Cardiazol Treatment and on the Present Application of Hypoglycaemic Shock Treatment in SchizophreniaBoard of Control for England and Wales / H.M. Stationery Office
Bibliographic and digitized record of the Board of Control's 1938 official report specifically evaluating Cardiazol treatment and shock treatment in schizophrenia.
Mental Treatment — House of Commons debate, 14 July 1938UK Parliament — Historic Hansard
Primary parliamentary record confirming that the Board of Control was preparing a government report on Cardiazol injections for schizophrenia as the new treatment spread through public mental hospitals.
The Medical Prescription of Patient OccupationPalgrave Macmillan / NCBI Bookshelf
Modern historical synthesis identifies Cardiazol as the most widely used somatic treatment for schizophrenia and affective disorders in British public mental hospitals and notes that the Maudsley barred trials because the induced convulsions caused extreme anxiety and fear.

Last reviewed: 24/08/2026