Hi again Loquat. I see you are still seeking ideas and answers to helping the people around you...especially the people you love. :)
I will agree with you that getting the nephew off of smoking weed is beneficial. Even though I feel sure he would disagree due to the fact that it may help with his anxiety, but may add to psychoses.
Since you have chatted with me before, I think you know that I advocate natural/alternative/foods as a way to heal. Unfortunately, some with mental illness are not looking for help that causes them to change their whole way of living their lives in order to feel better. Many just are not convinced it's worth the effort, nor do they have the energy to do so. Because of that, I have suggested to friends and loved one's a step stone approach to healing. It is not what I would call the "best" way to heal from a purist standpoint...but it's a stepping stone to get the most difficult with illness to go to the next step in a purer way of healing.
First off, I want to say I have no affiliation with this company and I do apologize that they can be a bit pricey. However, I have seen them do wonderful things with mentally ill people. So that is why I suggest their website. Also the way the company got started has a inspiring story about a man who has a very large family that was filled with bipolar misery and struggles. It tells of what he did to help them after his wife committed suicide.
Sometimes taking these supplements can be enough to show an ill person that alternative health can cure ailments that are said to be incurable. So once they start doing better, they then can take the next step of a more natural lifestyle.
Also, I have mentioned before the study of Dr. William Philpott and his research into using magnets as being very helpful with anxiety. Using the proper strength and type of magnet applied to the top of the head or base of the skull can reduce anxiety, insomnia and even Depression greatly.