Almost a third of people diagnosed with clinical depression do not respond to medication or talk therapy.
A potential treatment for this chronic or treatment-resistant depression is repetitive trans-cranial magnetic stimulation (TMS) which has been used overseas for more than a decade.
Dr Nicholas Hoeh and Kate Godfrey demonstrating rTMS Photo: supplied
Dr Nicholas Hoeh from the University of Auckland's faculty of medical and health sciences is lead researcher on the first clinical study of its use in New Zealand. He spoke to Kim Hill about why it should be considered a viable option for the treatment of depression.
"We were quite aware that there was a huge lack of access to TMS. It was quite striking, partly because in the university there was a TMS machine essentially unused. There was no provisions for it being used, there were no trained clinicians. It was just sitting there as a research device."
Dr Hoeh says he first came across TMS while he was working in the United States. When he moved here, it was unavailable despite being approved by the FDA.
"It was quite frustrating as a clinician working with people with depression and just knowing that there was this treatment available, but there was no access in New Zealand."
He and his team set up a pilot study exploring TMS use in the New Zealand context with 30 patients.
He explains that most of the brain communicates through electrical signals, and TMS provides a non-invasive and safe way of altering those circuits.
"There is this inter-relationship between electricity and magnetism - this was mathematically described back in 1855, so it’s not a new phenomenon by any means."
He says the machine is basically a large capacitor that generates electricity that goes through a coil which creates a magnetic force.
"That magnetic force can safely go through the skull without any disruption and minimal discomfort, and then it can target particular brain regions."
As an example, he says you could target the motor strip - the part of the brain that controls movement - and you can actually twitch the thumb muscles.
Most people say they can hear an annoying tapping sound when they undergo TMS therapy. Dr Hoeh describes it as feeling like a woodpecker tapping away.
Four people involved in the pilot study said they found it too uncomfortable to continue.
Dr Hoeh says they can’t say exactly why the treatment alleviates symptoms of depression.
"Unfortunately, the mechanisms around depression itself is not well-characterised, so lots of theories and guesswork. The brain is complicated, obviously, and without a fundamental underpinning to understand depression, it’s hard then to theorise the mechanisms for TMS.
"That being said, it does appear that there are certain areas of the brain that seem to be underactive or overactive, and by adjusting those circuits, it does seem to have some benefit."
As for why it’s not in wider use in New Zealand, Dr Hoeh says many Kiwis are unaware of the treatment and the New Zealand health system has not gravitated towards newer treatments in mental health.
Currently TMS treatment is available in only two or three private clinics in New Zealand. Dr Hoeh says it should at least be discussed as an option within the public healthcare system.
"The evidence is there, the approval is there and we know that there is a huge cost burden from depression and that many of the treatments that are available, people don’t respond to or don’t tolerate. So I think there’s lots of well established economic arguments that are in favour of TMS just in terms of reducing the overall cost burden and societal burden.
"For example in our study, we had two people who were in the in-patient unit with severe depression who were both responders [to TMS] and were both out of the hospital and recovered as a result of the treatment."
