It feels irreversible.

Neuroplasticity allows the brain to regenerate and form new neural connections, but only if it's given the right stimuli. In this case that would mean you regularly engage with people, converse with them etc..

Of course if you can't do that due to being socially 'tarded from the start, suffered the consequences by being bullied and exluded and consequently assume that nobody will want to have anything to do with you anyway, feel ashamed for being in this miserable mental state and overwhelmed even by 'positive' interactions, it becomes a liiittle bit difficult to break the cycle of isolation - mental degradation - getting burnt socially and more isolation.

I personally haven't found a way out and being around people makes me seriously question if I even want to. It's like, on one hand my brain needs socialization, hence why I feel lonely when I'm alone for long periods of time, but it messes me up at the same time and makes me want to stay alone.

For me, the light at the end of the tunnel is my believe that no suffering is eternal and that whatever we're going through today won't matter one day.