Hello Hazel58, glad you reached out for support. It sounds incredibly difficult to have a young adult child with BPD type behaviors -- too old for you to have more say about treatments, and yet too young to be making wise decisions independently.
Many parents here have struggled with having a child with BPD (diagnosed or not) and substance abuse issues. I know it isn't easier in a state where getting any number of drugs is incredibly simple.
I'm reading a mix of plusses and minuses about your son's situation:
On one hand, he still deals with severe depression/anxiety, can be suicidal, uses alcohol and pot to cope, has extreme screaming and crying episodes, and is incredibly impulsive. So much for any family to deal with.
On the other hand, he did call 911 on himself, can be apologetic, was cooperative with seeing a psych and therapist, had some significant compliance with meds and treatment, has discovered less helpful treatment modalities (i.e. group therapy isn't a good fit for him, so no more pursuing that), had a psych who identified BPD as a key issue, has some motivation to get out and go to school, and has a treatment team that works with you for med management. These are some glimpses of hope.
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I think I'm reading that one top issue for you right now is him driving while high? In terms of driving, do you own the car?
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And another top issue is, as your T suggested, figuring out a specific plan for what to do if he has another huge episode (I'm guessing verbal abuse, screaming, crying, self harm)?
I think you may be on to something here:
We want to avoid police and hospitals unless he obviously plans to hurt himself. He is extremely impulsive. What do people do? Do we get him a hotel room or something?
Giving family members space from each other when one is "unreachable" (due to having an emotionally extreme episode) is often something people do. One positive thing about that choice is that it removes targets from the pwBPD and gives them room to practice soothing themselves. It can be a kind thing to not stick around to be targeted with verbal abuse. However, it is challenging because your son may need supervision to be safe. If he had the hotel room, a plus side is it might be harder for him to access his "home things" like drugs or alcohol. On the minus side, he may be very destructive to the room. If you had the hotel room, similar pluses and minuses: you are removed from being his target, yet he is at home unsupervised.
What is your sense of how he would do unsupervised in either location? He is a unique individual, so while some pwBPD might still act out/be destructive in a hotel room, other pwBPD might find it more soothing and calming because it's away from triggering situations.
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Do you have other family members at home (spouse, other kids)? What is your son's relationship with them like? I heard you saying that because you manage his meds, he tends to lash out at you -- does he have a better "working relationship" with others?
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Lots of questions for starters, so I'll wrap it up here. I just want you to know that with the holidays coming up, please know that you can give yourself a break if things don't go the way you'd hoped. Many families wish that "everyone could be together" at Christmas, for example, but sometimes crises happen. Know that you are doing the best you can, no matter how the holidays turn out. I hope you can find some moments of peace and relaxation in the next few weeks.
Let us know how you've been doing;
kells76