Also, do you have reliable sources for this poisoning hypothesis?
Medical issues related to toxic exposure are medical issues, not something that can be resolved by psychotherapy.
See my other post on how to find those reliable sources, or just ask your doctor if this ever happens.
ADHD is irreversible, it's not something that can be reversed or goes away on its own.
There is literature on a link between fetal heavy metal exposure and ADHD development.
I can't find anything on neurotoxins "mimicking" ADHD.
Again, by the very biological definition of what happens in a brain on ADHD, this is not reversible. It's chronic.
Sources:
1: https://my.clevelandclinic.org/health/diseases/neurotoxicity
2: https://pubmed.ncbi.nlm.nih.gov/36972880/
Medical issues related to toxic exposure are medical issues, not something that can be resolved by psychotherapy.
See my other post on how to find those reliable sources, or just ask your doctor if this ever happens.