Hi! I believe I can be of help with this issue.
First, let me say I can imagine how frustrating and worrisome this situation must be for you. On the one hand your son is an adult and needs to be treated as one and he legally is allowed to be delusional and dysfunctional without having treatment forced on him unless you, the family, go through the sometimes difficult legal proceedings of having him ruled not mentally competent. But on the other hand you are clearly a very loving and caring parent and you know he needs help and it feels so helpless.
And this is actually the key to my answer to you that you need to consider and think about. Your son almost certainly has a thought disorder such as schizophrenia. And he desperately is need of professional treatment.
Your observations seem correct. You are right that his attempt to be independent is only hurting him and not helping. But it is important for you to not become adversarial about this. To have him feel that you are on his side. Why?
Because taking meds, staying true to treatment, and staying stable, is his lesson to be learned and he will not learn it from having people telling him he's sick when he believes with 100% certainty he's fine and everyone else is wrong. He will become defensive. So it is vital for you not to take your son's situation personally and to always make him feel as if he is in charge of himself. This condition is called anosognosia and is unfortunately rather common with severe mental illnesses such as schizophrenia.
Because of the mental illness one of the problems here is that with many schizophrenia disorders sufferers, manipulating the situation to avoid medication or treatment in general is part of the disorder. It is very pernicious and very difficult to treat. I would like to recommend to you the work of Dr. Xavier Amador. I think that in this area of treatment resistance he has been invaluable to all of us working with schizophrenia. I have found it very valuable and I think you will see its value as well. His whole approach is to find the way to make treatment a win-win situation. Because for your son, treatment at first may be only for others' sakes: family, doctors, etc. Not for himself. The meds probably will indeed cause whole sorts of side effects he doesn't like. And this is going to be true of any meds the doctors come up with. Because resistance is often part of the illness and all meds have side effects.
So this approach can help you very much. But not only you personally, but the whole family. Here are his two most known books:
I am Not Sick, I Don't Need Help. This is the book that made Dr. Amador famous. It details a bit the story of his brother, who will remind of you of Leo probably in some aspects. Amazon page for it:
The other book is I'm Right You're Wrong, Now what? Break the Impasse and Get What You Need. Amazon page:
Here is his organization's website that has wonderful resources available:
Okay, I wish you the very best!
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