Electroconvulsive therapy (ECT) has unparalleled efficacy in treating severe depression, and is also useful in treatment-refractory cases of schizophrenia and obsessive compulsive disorder (OCD). However, its use is limited by significant adverse effects on memory and cognition. In addition, ECT cannot be precisely targeted, since it relies on unpredictable pathways of electrical conduction through the brain. Magnetic seizure therapy (MST) is currently under investigation as a targetable, cognition-sparing alternative to ECT. MST uses magnetic fields rather than electrical stimuli for seizure induction, dramatically reducing the passage of induced current through undesired brain regions. 10 years of experimental studies have established the safety of MST in animal and human subjects. This pilot study will investigate whether MST has similar efficacy to ECT, with fewer cognitive side effects, in patients with severe depression, schizophrenia, and OCD.

Although ECT is effective against severe depression, psychosis, and OCD, it also produces significant impairments of autobiographical memory and other cognitive functions. These side effects limit the acceptability and tolerability of ECT in many patient populations. They also limit the number of treatments that can be administered in a course of ECT, leading to high relapse rates once ECT is discontinued. In animal studies, MST has been shown to have far fewer adverse cognitive effects than ECT. In small human studies, humans have shown faster subjective and objective recovery of orientation after MST than with ECT. However, the precise degree of cognitive sparing in MST versus ECT has yet to be established. Likewise, the comparative efficacy of MST versus ECT in severe depression, schizophrenia, and OCD remains to be seen. The investigators aim to determine whether MST spares autobiographical memory and other cognitive functions, while retaining comparable efficacy to that of ECT.

Objective 1: To compare the efficacy of MST and ECT in treating patients with severe depression, schizophrenia, and OCD.

Hypothesis 1: MST will have equivalent efficacy to ECT on objective measures of mood, schizophrenia, and OCD symptoms.

Objective 2: To compare the effects of MST and ECT on autobiographical memory and other cognitive functions in patients with severe depression, schizophrenia, schizoaffective disorder and OCD.

Hypothesis 2: MST will have significantly lower adverse effects on objective measures of autobiographical memory and other cognitive functions in patients with severe depression, schizophrenia, and OCD.

Objective 3: To compare the changes in brain function that result from MST and ECT.

Hypothesis 3: Both MST and ECT will produce changes in functional brain activity consistent with antidepressant response, antipsychotic response, and antiobsessive response, along with a sparing of cognitive functions.

The discovery of a viable alternative to ECT, with equivalent efficacy but fewer side effects, would have a transformative effect on the treatment of several forms of severe mental illness. At present, many patients who could benefit from ECT do not pursue this treatment due to concerns about cognitive side effects, as well as the enduring social stigma of ECT itself. In addition, many patients who have benefited from ECT are obliged to discontinue this effective treatment because of mounting cognitive side effects; high rates of relapse then ensue.

If MST could be shown to spare autobiographical memory and other forms of cognition, many more patients would be willing to take advantage of the treatment. They would also be able to continue the treatment, when effective, for longer periods. The potential result would be a dramatic improvement in the rates of remission and relapse for patients with severe depression and other forms of mental illness.

Inclusion Criteria:

• ages 18 to 85
• DSM-IV diagnosis of major depressive episode with or without psychotic features in the context of MDD or bipolar disorder; OCD or Schizophrenia
• 24-item HRSD score of ≥ 21 (for depression subjects)
• 18-item BPRS score of ≥ 37 (for schizophrenia subjects)
• Y-BOCS score of ≥ 16 (for OCD subjects)
• demonstrate capacity to give informed consent
• are a Canadian resident

Exclusion Criteria:

• have an unstable medical and/or neurological condition
• are currently pregnant or lactating
• are not considered sufficiently well to undergo general anesthesia for any reason
• have a cardiac pacemaker, cochlear implant, implanted electronic device or non-electric metallic implant
• are taking a benzodiazepine at a dose greater than lorazepam 2mg or equivalent
• are taking any non-benzodiazepine anticonvulsant
• have active substance misuse or dependence within the past 3 months
• have a current diagnosis of delirium, dementia or another cognitive disorder secondary to a general medical condition
• have a co-morbid borderline personality disorder and/or antisocial personality disorder
• have had a history of any suicide attempts in the past 6 months