Psychotherapy is an effective treatment for major depression. There are several standardized forms of therapy that work well for depression, including cognitive behavioural therapy, interpersonal therapy, and mindfulness-based cognitive therapy. However, privately funded therapists can be expensive, and publically funded therapists tend to have long waiting lists. With so many millions of Canadians suffering from depression, even a huge increase in mental health funding still might not be enough to provide effective one-on-one therapy to everyone who could use it.
Even for those who can get access, psychotherapy is hard work. There are appointments to be kept, skills to be learned, exercises to be done, and habits to be overcome. For many people with severe depression, simply finding the energy and motivation to get out of bed can be a challenge. It’s a Catch-22 situation: to get out of depression, you need therapy, but to do therapy, you need to get out of depression. In this all-too-common scenario, other kinds of treatment are needed to break the impasse.
With major depression being so common and so disabling, antidepressants are among the most widely prescribed of all classes of medications today. Many people find antidepressant medication to be effective in lifting their mood, and restoring their lives to a healthy level of function. The convenience of medications is also hard to beat: compared to many other treatments, they are relatively inexpensive, require little time commitment, and have relatively minor side effects for many people.
Unfortunately, more than a third of all individuals with depression cannot find a medication that helps them. Others find the side effects of medication to be intolerable, or are uncomfortable with the idea of taking antidepressants in the long term. Even among those who do respond to treatment, a large proportion relapse into illness once again. For people in these situations, a third option is available: direct stimulation of the brain.
Depression is sometimes described as a chemical imbalance in the brain. However, it is important to remember that chemical substances affect our thoughts, emotions, and behaviour by altering the patterns of electrical activity in the neurons of the brain. Since the brain’s neurons communicate with one another by electro-chemical signals, they can also be affected by electrical stimulation.
The effects of electrical stimulation on the nervous system have been known since the middle of the 18th century. The abnormal electrical discharges of epileptic seizures can cause abnormal movements, sensations, thoughts, and emotions — even disruptions of consciousness itself. In the middle of the 20th century, the Canadian neurosurgeon Dr. Wilder Penfield famously used electrical stimulation to map out and avoid the brain regions that control important functions like speech, movement, or vision, in patients undergoing surgery for epilepsy. Today, neurosurgeons such as our own Dr. Taufik Vailante at the Toronto Western Hospital still use modernized versions of these techniques.
As we saw in the previous section, not only are there specific networks of brain regions for speech, vision, and movement. There are also specific networks of regions that are important for decision-making, impulse control, emotion regulation, self-reflection, and social interaction. If these brain regions fall into abnormal patterns of activity, their owners can start to develop problems with mood, judgement, behaviour, self-image, and social behaviour.
These are the types of problems that are traditionally considered “psychiatric” rather than “neurological”, even though in the end they all arise from dysfunction in the nervous system. In the past, psychiatrists mostly treated these types of illnesses with either therapy or medication. Today, however, patients have access to an increasingly wide range of treatments that bypass brain chemistry altogether and act directly on the activity of target brain regions. These treatments are sometimes described with a collective term, neuromodulation.
Neuromodulation Treatments for Depression
In Canada, there are currently four main types of neuromodulation in use as treatments for major depression:
+ Deep Brain Stimulation (DBS): uses stimulator electrodes, neurosurgically implanted in emotion-regulating regions of the brain
+ Electroconvulsive therapy (ECT): uses external electrodes, applying strong pulses of current to produce a seizure in the brain under general anesthesia
+ Repetitive transcranial magnetic stimulation (rTMS): uses external magnetic field pulses; more effective than medication, less effective and less invasive than ECT
+ Transcranial direct current stimulation (tDCS): uses very mild electrical currents; least invasive, but its effectiveness against depression is still unclear
These treatments cover a spectrum of trade-off between effectiveness and invasiveness. At present, the most powerful treatments for major depression are deep brain stimulation and electroconvulsive therapy. Unfortunately, both techniques have drawbacks that limit their use, despite their effectiveness.
Deep brain stimulation (DBS) is currently the most powerful known treatment for major depression. The technique itself was developed at the Toronto Western Hospital nearly 10 years ago. It was based on research findings by neurologist Dr. Helen Mayberg, working with a multi-disciplinary team that included world-renowned neurosurgeon Dr. Andres Lozano, our own Clinic’s Co-Director, Dr. Peter Giacobbe, as well as UHN’s Psychiatrist-in-Chief, Dr. Sidney Kennedy. Because DBS can often achieve remission where all other measures fail, the tecnhique is now being used to treat severe depression in advanced medical centres across Canada and around the world.
With DBS, a neurosurgeon implants a pair of electrodes into a small brain structure that is overactive in depression, called Area 25, or the subgenual cingulate. The electrodes stimulate at a high frequency that effectively jams the signals passing through the neural connections in the region. Once the electrodes are activated, many patients experience a rapid and dramatic improvement in symptoms — even patients who have not responded to any other treatment, including ECT. However, DBS remains an experimental technique, available only to small numbers of patients, in medical centres with expert teams of neurosurgeons. It also requires the electrodes to be permanently implanted in the brain and connected to a battery implanted under the collarbone — quite an invasive procedure compared to other treatments for depression. For these reasons, DBS is usually reserved for cases where all other options have failed.
ECT is the second most powerful brain stimulation treatment, achieving remission in 65-75% of patients with depression, and even higher rates in certain subtypes of depression. ECT was first developed in the 1930s after psychiatrists noticed that patients with epilepsy sometimes had dramatic improvements in their symptoms in the aftermath of their epileptic seizures. The original idea behind the technique was to induce a seizure artificially in patients who did not have epilepsy, so that their symptoms might improve in the same way.
Modern ECT uses powerful pulses of electric current to induce a seizure in the brain. To ensure that the patient does not suffer pain or injury during the procedure, ECT is performed under general anesthesia, with careful monitoring of vital signs, much like a surgical operation. ECT is very effective against depression, but can have side effects on memory function that are quite disturbing for some people. Because of the need for general anesthesia, the cognitive side effects, and an enduring stigma around the technique, many patients do not consider ECT to be an acceptable treatment option, however effective it may be.
Transcranial direct current stimulation (tDCS) uses extremely mild electrical currents to stimulate the brain through large, adhesive electrode pads attached to the scalp. The currents in tDCS are nearly 1000 times weaker than the ones used in ECT — far too little to produce a seizure. Patients remain awake during the proceudre, and usually feel nothing more than a mild tickling sensation, if anything at all. Inside the brain, however, the neurons do respond to the mild currents. Neurons under the negatively charged anode are gently stimulated, while those under the positively charged cathode are gently inhibited. Although stimulation is usually applied for only 20 minutes, the effects can persist after the electrodes have been removed.
tDCS is still an experimental technique. So far, some studies have found that it helps with depression, while others have found no effect. It is still unknown whether tDCS would work better with slightly stronger doses, or more frequent treatments. There are still many parts of the brain that have never been stimulated with tDCS for depression, and the best site for stimulation is still unknown. So tDCS is promising for its ease of use and lack of side effects, but it remains to be seen whether tDCS is actually much help in treating depression. For the moment, tDCS has not yet been approved by Health Canada.
So: DBS is extremely effective but requires neurosurgery. ECT is also effective but hampered by stigma and side effects on memory. tDCS is free of side effects, but may or may not turn out to have any positive effects. That leaves repetitive transcranial magnetic stimulation (rTMS)— the treatment we offer in this Clinic.
rTMS for Depression
Since we are an rTMS clinic, after all, we have devoted an entire section of the website to explaining the history of rTMS, and how it uses magnetic pulses to stimulate the brain, thus correcting the abnormal patterns of activity that underlie many neurological and psychiatric disorders.
We have also devoted a section to explaining how rTMS (and other treatments such as psychotherapy or medication) can help to free the brain from depression. To learn more about how these treatments work on the depressed brain, click here.