Lily,
I have used the M1 on my head while I slept and I am coming off of brain problems and I think it has helped me with brain plasticity.
The one side effect I have had was vertigo, probably from knocking calcium crystals around in my ear and there is a matter of coil placement and I genuinely believe that is a serious enough matter to be careful of where you put the coils.
You might go to PubMed and read studies on things like TMS. I say that because some coil positions for some things really do matter. For instance, when they studied depression, the right side and left side of the prefrontal cortex worked differently. It has been a few years since I looked it up, but with the brain, the setting and coil position do matter.
If you have anything like mental health issues particularly, go through the literature to learn about it.
For example, some studies intentionally use Gamma and some use Alpha and some conditions will say that a certain part of the brain is low in Theta or high in something else.
Don’t neglect the research is my advice.
Still, we are all self-hackers using a research tool on ourselves and I have slept with it and other than vertigo once I haven’t had anything negative.
I also have used it on my vagal nerve all night and that would be a good topic for you.