| Paper authors: | David Long, Daniel Blumberger, Zafiris Daskalakis, Jonathan Downar, Fidel Vila-Rodriguez |
| Year of paper publication: | 2021 |
| Post authors: | Alice Erchov, Sarah Kesler, Fidel Vila-Rodriguez |
| Download the research article: | Long (2021) Left-handed individuals with treatment-resistant depression show similar response to intermittent theta-burst stimulation and 10 Hz repetitive transcranial magnetic stimulation |
The Question
Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive neurostimulation therapy that works by delivering painless magnetic pulses to the brain via a coil placed on an individual’s scalp. rTMS has been proven as a safe and effective way to treat depression, even for those who did not improve with medications or therapy.
The level of rTMS magnetic stimulation is also personalized to each individual, found using something called the motor threshold. The motor threshold is the minimum amount of stimulation intensity needed to make an individual’s right hand make a small twitch. For an example of what this looks like, you can see this youtube video.
Interestingly, handedness (i.e., whether an individual is right or left handed) might indicate which side of the brain/body is more dominant. Potentially, this could affect the intensity of stimulation that left or right-handed people need. Additionally, rTMS is delivered to the left side of an individual’s head. This region of the brain controls the right side of your body — raising the question as to whether rTMS is equally effective for left and right-handed people. This could have important impacts for depression treatment.
The Answer
Previous researchers pooled results from 11 studies that found that rTMS was more effective for left-handed people, with a greater proportion and strength of depression improvement when compared to right-handed individuals. Researchers at NINET Lab wanted to replicate this finding in a larger group of individuals — 381, to be exact.
What the NINET Lab found is that there was no difference in depression improvement in response to rTMS when comparing left and right-handed individuals. This was true even when accounting for sex, age, employment status, baseline depressive severity, level of treatment-resistance, and length of depressive episode.
The Conclusion
Our results may differ from previous research because pooling data from 11 different studies is challenging. Each study may have looked at different kinds of people, depression severities, treatment approaches, procedures, etc. — which may have made them incomparable (like comparing apples to oranges). By looking at a large group of people all from the same study, the NINET Lab results adds to our confidence that left and right-handed people equally benefit from rTMS. This means that any eligible person may benefit from this potentially life-changing therapy.