How or if to respond

I think you'd be acting in your own best interests - and rightfully so - to just let this die naturally by not getting back in touch with him. It's clear you feel a certain sense of responsibility for this guy but you can't prioritise his needs at the expense of your own. By your own admission, you get literally nothing out of this friendship and never have. If it wasn't for his mental health issues, you likely would have walked away years ago. I have genuine sympathy for his challenges but you can't carry someone indefinitely just because they have issues. Especially ones they can't/won't make a genuine effort to address.

I think you should walk away from this guy and do so with a clear conscience.

His family are largely responsible for him being the way he is? I didn’t know a family could cause a mental illness. But anyway you’ve given him so much pity and time already, which is admirable, but possibly also slightly enabling. It might be the kindest thing for you both to step back from this.

Yea I'd agree with the above posters. It's time to move on.

I'm a very compassionate person but even I can't see any merit to you returning to being his friend.

As we get older, we learn that to preserve our own self care is the most important thing.

You have a family, job, other friends. All positive.

Quite frankly, you don't need this guy dragging you down.

He's not your responsibility, not your project.

You have given more than enough of your time, energy, kindness.

Him ghosting you for a few months was a blessing in disguise. It's a natural break away.

Leave it be now.

It is an easy place to be. Cut contact.

I'm quite compassionate, but I'd be cutting free immediately. I'd also have no guilt. I had done my best.

I would cut the ties after writing to this friend that he needs to take his doctor's advice and recommendations seriously and to get his head fixed. You may lose the friend. However, this could be a kick in the backside he needs to progress towards recovery. Or it may break him. Mental illness is a bitch.

OP, you have given a lot of time and energy to this relationship. I agree with other posters who suggest you call it a day and disengage.

I'm wondering though how someone like your friend can be helped? (Maybe that's a topic for a whole new thread). There appears to have been no shortage of professional help given to him and all to no avail. What can be done when someone refuses to take advice and make some effort to help themselves? I'm sure some alcoholics and drug addicts are like that too. When someone takes their own life their family and friends all feel they should have or could have helped more. Perhaps some people are, sadly, beyond help? So many of us complain of the lack of help, services and support for mental illnesses. This thread has made me and perhaps others realise that there is only so much anyone can do to help such a person. It's sad but realistic too and hopefully will help the OP to accept that he has given all he can to this relationship. The mind has taken control of his friend and unfortunately there are impenetrable barriers in place.

The 5 months break from this guy taught you two things. The first is that you enjoyed the break from him. That speaks multitudes in itself. The other is that he managed to live his life for 5 months without you. Like just about everyone here, I think it is time for you to move on from this guy. He may have been a friend at some point long ago but what exactly is he to you now? I get the impression that there's a lot of guilt and obligation thrown into the mix now, despite your attempts to establish boundaries. I think you've been handed a golden opportunity to cut contact with him after all this time.

Although ignoring his email might work, I have a feeling that he'll miraculously rediscover all these other ways to contact you. It's up to yourself how you handle this but you might end up having to write a message like Nudain has described. Personally, I'd be devastated to get something as blunt as that but maybe that's the only language he'll understand. You could so easily get sucked back into this guy and his problems. Despite you trying your best to help him, you're not a trained professional and perhaps you're unwittingly hindering him as much as helping him.

Childhood trauma? Ummm no... I actually have BPD. It's hereditary. Also it's not an excuse merely a reason.

Anyway. The friend needs to chill out and stop worrying so much. Most of this person's issues they have created themselves. Their fears are illogical as is their thinking. Most of what they think isn't even true but they tell themselves it is. They need to come to term with their condition and stop running. What needs to happen is this person's friend needs to appreciate and apologise to them. They must admit their weakness and seek to fix it. Not constantly make every excuse they can think of. Ghosting a friend for so long is unacceptable and cowardly. This friend needs a sit down and a serious conversation. They need to understand they will lose the relationship if they don't buck up.

They must be honest and speak about what they fear not keep it hidden away to grow like a big monster.

Yep most people with the condition never learn and always blame everyone but themselves. Only once you realise you are the root to your own happiness you will always feel lost.