Derealization is also associated with the presence of an arachnoid cyst.
Are these arachnoid brain cysts? If so, the symptoms that may occur are numerous depending on the size and location. Going from your list of symptoms, an arachnoid cyst may cause:
*Headaches
*Vertigo/dizziness
*Depression
*Anxiety
* Mental status includes confusion, difficulty in going to sleep or remaining asleep, general apathy and feelings of depersonalization
Some of the symptoms can be those of a thyroid condition. Please post results to whatever thyroid function tests were done and be sure to include reference ranges, since those vary lab to lab and must come from his own report.
Even labs in a "normal range" may not be normal for the individual.
They should, at the very least, have done Free T3, Free T4 and TSH. Hopefully, they would also have done thyroid antibody tests to determine if there were an autoimmune disease destroying the thyroid.
FYI - there are no "natural" remedies for hypothyroidism, so if the naturopath thought there was a thyroid condition, s/he should have started him on a thyroid replacement medication. Not sure what "cell salts" even are, but that's quackery at its finest.
If the tests I mentioned above were not done, your boyfriend would need to get them done in order to determine whether or not he has a thyroid condition. If he needs to have them done, we can point you to a couple of web sites, from which the FT3, FT4 and TSH can be ordered for about $85, which is less than most labs would charge and wouldn't entail another doctor visit to get a lab order.