Depression is a complex neuropsychological disorder. We’ve yet to pin down the exact mechanisms behind depression, but we know a few things: people with major depressive disorder seem to have physiological (smaller brain regions, abnormal hormones) and genetic differences that put them at a higher risk for having a depressive episode.
While we don't understand everything about depression, that doesn’t mean we don’t have treatments for it. Some of the first-line treatments for depression include pharmacotherapy (overwhelmingly SSRIs) or psychotherapy (mainly CBT).
There's no doubt at this point that SSRIs are effective, but they are often accompanied by several side effects that can be problematic. CBT, on the other hand, is not easily accessible by all and requires a long time to work.
A *relatively* new FDA-approved therapy for depression, known as transcranial magnetic stimulation (TMS) uses a magnetic field (by placing a magnetic device on one’s head) to increase brain activity in some areas of the brain. It’s often been compared to the most effective depressive treatment currently around, electroconvulsive therapy (ECT). ECT is considered the “gold standard” for treatment-resistant depression but carries several side effects, such as negatively impacting neuropsychological function.
While TMS is not as effective as ECT, it doesn’t carry many of the side effects of ECT. In fact, it may improve cognition, independent of the relief from depression (depression can negatively impact cognition). TMS also has very few side effects compared to treatments like SSRIs.
The evidence to suggest that TMS is effective for depression is decent. There are quite a few randomized controlled trials comparing TMS to sham TMS, which find it to be a clinically significant treatment. When combined with antidepressants, it produces an effective intervention.
However, there are some caveats. There are known problems with the controls that are used in TMS studies, AKA the “sham TMS,” in that a lot of the time, people can guess what treatment they got, despite having been blinded. This is a source of bias and a potential problem. The other caveat is that the effects of TMS seem to be short and not very large, but it’s worth keeping in mind that it’s still a very promising treatment.
I summarize some of the evidence below from some RCTs and systematic reviews of RCTs.
Note: There are different types of TMS, and they all have different magnitudes of effects, so it’s worth reading the studies if you’re interested in a kind.
Some Randomized Trials:
|Improvement in quality of life with left prefrontal transcranial magnetic stimulation in patients with pharmacoresistant major depression: acute and six month outcomes.||301||6 weeks||Quality of Life||Significant improvement|
|The efficacy and safety of low frequency repetitive transcranial magnetic stimulation for treatment-resistant depression: the results from a large multicenter French RCT.||170||2-6 weeks||Hamilton Depression Rating Scale||As effective as antidepressants|
Systematic Reviews of Randomized Trials