Written by Dr. Yogesh Thakker, Consultant Psychiatrist and Medical Director, Manor Clinic
Depression affects a large number of Canadians, and for many people antidepressant medication and psychological therapy work well. For others, symptoms persist despite adequate trials of treatment. When that happens, patients and their family physicians often ask what other options exist.
Transcranial magnetic stimulation, usually shortened to TMS, is one of them. This article explains what TMS is, how a course of treatment works, and what the current evidence does and does not tell us.
What TMS is
TMS is a non-invasive treatment that uses magnetic pulses to stimulate a specific area of the brain. A coil is placed against the scalp, and the magnetic field passes through the skull to produce a small electrical current in the brain tissue underneath. The target for depression is usually the left dorsolateral prefrontal cortex, an area involved in mood regulation that tends to be underactive in depression.
The treatment does not involve medication, sedation or anaesthetic. Patients remain awake and alert throughout, and can drive themselves home and return to their usual activities immediately afterwards.
TMS has been authorised by Health Canada for the treatment of depression since 2002, and repetitive TMS is recognised in Canadian clinical practice guidelines for major depressive disorder.
How TMS differs from electroconvulsive therapy
This is the question I am asked most often, and the two are frequently confused.
Electroconvulsive therapy (ECT) is delivered under general anaesthetic, induces a seizure deliberately, and can cause memory effects. It remains an important and effective treatment, particularly in severe illness.
TMS does not induce a seizure, requires no anaesthetic, and does not cause the memory effects associated with ECT. The magnetic field is focused on a targeted area rather than affecting the brain as a whole. They are quite different procedures.
What a course of treatment involves
A course of TMS is a commitment, and it is worth understanding that before starting.
Treatment is delivered in a series of sessions, usually five days a week over several weeks. The exact number of sessions and the length of each session depend on the protocol used. Some newer protocols deliver stimulation in a few minutes; conventional protocols take longer.
The first session includes a mapping process, in which the clinician determines the individual’s motor threshold, the amount of stimulation needed to produce a small movement in the hand. Treatment settings are then calculated from that measurement, so the dose is tailored to the individual.
During a session, patients sit in a chair while the coil delivers pulses. Most people describe a tapping sensation on the scalp and a clicking sound. Many read or listen to music.
Possible side effects
The most common side effects are scalp discomfort at the treatment site and headache. These are usually mild, tend to settle over the first week or two of treatment, and generally respond to simple analgesia.
Seizure is a recognised but very rare risk. Careful screening before treatment identifies factors that increase that risk.
TMS is not suitable for everyone. Metal implants in or near the head, including certain aneurysm clips, cochlear implants and some stimulators, are contraindications. A full screening assessment before treatment covers this.
Because TMS does not circulate through the body in the way medication does, it does not cause the systemic side effects some patients find difficult with antidepressants, such as weight change or sexual side effects.
What the evidence shows
Repetitive TMS for depression has been studied extensively, and its effectiveness has been examined in multiple meta-analyses. Reported response and remission rates vary considerably between studies, depending on the population studied, the protocol used and how outcomes are defined.
The honest summary is that TMS helps a meaningful proportion of people who have not responded to medication, that it does not help everyone, and that response cannot be predicted with certainty for any individual before treatment. Any clinician who tells you otherwise is overstating what the evidence supports.
Research into TMS for other conditions, including obsessive compulsive disorder, is ongoing, and regulatory authorisation differs between conditions and between countries.
Access in Alberta
Alberta has a publicly funded rTMS program for adults with treatment-resistant depression, and it is worth asking your family physician or psychiatrist about that pathway. TMS is also available privately, and private treatment is not covered by Alberta Health Care Insurance, so patients should ask about cost before proceeding.
Is TMS right for me?
That question can only be answered through an individual psychiatric assessment. Suitability depends on the diagnosis, what treatments have already been tried and at what doses, current medications, medical history, and screening for contraindications.
If you think TMS might be relevant to you, the first step is a conversation with your family physician, who can discuss whether a referral for assessment is appropriate.
Manor Clinic does not provide emergency services. If you are in crisis, please contact Access 24/7 at 780-424-2424, the Distress Line at 780-482-4357, or text CONNECT to 741741.
This article is for general education and does not constitute medical advice. It is not a substitute for individual assessment by a qualified health professional.
