There are no coils that can go 5.cm into the brain. There are several scientific articles about locations for stimulation, other about coil design for deeper stimulation. The coil used for the rTMS approved in Europe, USA and elsewhere have a stimulation depth of 1.cm. Coils that can go deeper was not developed until 5.years ago and are yet not approved for clinical use. They have been used for research until now and one have just been approved in the USA for OCD. The response rate for depression with normal rims is around 50% at two locations with the coil used. Research have shown that other with depression have regulation of emotions in structures deeper in the prefrontal cortex and when they are given rTMS at these two other locations with a deep coil they have a response. So, you might cure 85% of depressions if you also use a deep coil at other locations. There is only one place in Europe where they use such a coil. Because it is not approved for clinical use they are breaking the law in a way by using it. I think they might have said that the size of the trials in depression where such a coil is used makes it sufficient for them to use. It has been approved in the US to use this year for OCD. I have seen videos by a psychiatrist in New York from 2017 with such a coil used on a patient. It was not legal then. I think they have got these coil though connections to research facilities at universities. So, it is a research facility that have ordered from the producer and not a rTMS clinic. It might explain why the are almost absent elsewhere.
The rTMS researcher who works with depression, Jonathan Downar have addressed this problem about stimulation depth, locations and coils years ago. He writes this about the right VLPFC;
"The VLPFC also presents a challenging target for conventional rTMS,
as much of it lies deep within the frontal operculum, or along the orbital surface of the prefrontal cortex. However, even for superficial VLPFC regions, tolerability remains a problematic issue, due to the proximity of the extraocular and temporalis muscles. There are several alleviating measures that may be effective in improving the tolerability of stimulation at this region, as reviewed in detail below. With appropriate measures to alleviate discomfort,
conventional figure-8 coils may be suitable for stimulating some VLPFC regions, and newer coil designs should be able to address the depth-of-target issue in future. Hence, the VLPFC could also serve as a practical target in future studies of rTMS for depression, with appropriate refinements to technique."
https://dribrahimyilmaz.com/wp-content/uploads/Depresyonda-TMS-Tedavisi-Akademik-Makale.pdf
You psychiatrist might mean that the effects of stimulation might go as deep as 5.cm. There he is right. When you stimulate an area it will have affects on areas It is in networks with that is much deeper into the brain. But, a direct stimulation might that can go 5.cm might never be possible to develop as it will diffuse from the areas it shall pass (it will affect them too) and the stimulation will also spread over a larger area and become weak. Around 2-2,5.cm for a coil for deep rTMS is likely maximum and H-coils design for a specific locations might go close into 3,5-4.cm the brain.
In Western Europe a rTMS session can very in price between 100.euros to 300.euros. In the UK it close to 300.euros. In Eastern Europe from 50-55. euros.
He is right to call out a placebo effect. But, the TPJ trial was much larger is size than the right VLPFC. In depersonalization the placebo effect is much smaller than in depression. To see reductions of 20-50% in depression trials relate to placebo is normal. That is also why many says that SSRIs don't work for depression because the response rate in placebo group is very high in in many trials. But, the placebo effect in other conditions is much smaller. In obsessive conplusive disorder the placebo effect is much less and a response of 25% is regarded as valid. It is not the case in depression trials. Depersonalization placebo effect is similar to obsessive compulsive disorder. It is there but low and likely not sustainable over time. You can see it on the posts of this forum. Some tries a drug and makes a post here a day after about feeling better. It is often drug that are normally many weeks to work and in larger doses than tried. But, people feel better. Here on the forum they can not understand a week or two later that is stopped working. It is the placebo effect that stopped working. Many posts about feeling better on something also changes within weeks. So, the placebo effect is there but it do not last for a very long time. Never take posts from anyone who have taken a drug for a very few weeks seriously.
But, the reductions in a TPJ trial is much larger in those who respond. The problem with all trials in depersonalization is they are very small and not placebo controlled. Likely due to lack of funding into research into depersonalization. That is a problem. A bias from the researcher can also play a role. They hope their patients gets better and want to see a response. So, their perceptions can color the trail.
I think that that the right TPJ might play a role but is not the "core" location. It is likely in network with it and it might have some effect in some. The angular gyrus trial is with a 100. patients and half of them will get placebo. So, it the first real trial in depersonalization ever. If the rumor holds that the response rate is 50% it might again be related to networks connections. There is a locations that turns up in many studies with drugs that can make depersonalization and that is also found larger in people with symptoms with depersonalization. It is also connected to and close to angular gyrus and the TPJ. That is a location called "Precuneus". In a PET study from 2000 it came out as active along with the angular gyrus and TPJ. It is found larger in in MRI study at the depersonalization research unit. In people with borderline disorder with dissociation it is also affected. When people are given sedation and lose consciousness, it is turn off. Drugs like ketamine and cannabis that can make depersonalization highly effects this location. But almost all drugs that have affect the the consciousness affect the precuneus. It plays a centrai role in consciousness and self-awareness.
There was a publications in "Nature" this year about a experiment where mouse was given ketamine and immobilized into dissociative state. They found an area changes the frequencies in the brain called "Retrosplenial" in mouse. The same area in humans are called "posteromedial cortex" and coveres two locations; precuneus and posterior cingulate cortex. In publication about the effect of cannabis those who experienceed a bad trip with depersonalization, anxiety, ego death found to have changes in frequencies in the precuneus and prosterior cingulate/posteromedial cortex.
https://www.ecnp.eu/presentationpdfs/68/P.1.b.009.pdf
I hope that angular gyrus trial might go into the role that the precuneus might play. You need a deep coil to stimulation of this area.
