This guys anxiety is general anxiety and not relationship based. Like he had the chance to take a really great trip, but backed out last minute because his anxiety got the best of him .
You might stay aware that anxiety this extreme might be social anxiety, or it MIGHT be OCD. People with OCD get very anxious. I'd be curious if the backing out at the last minute was because he was overwhelmed at the thought of the amount of socializing that would be required - or if he had OCD concerns like phobia of flying, germs, etc.
I'd also be interested in what kind of treatment (and how long) he has had. If this is a recent development and he's getting treatment, that's one thing. If it's a lifelong problem that has kept him from being a productive member of society that's a whole other ball of wax. Not saying that he couldn't be a lovely guy or that he doesn't deserve love - only that taking on someone with those challenges might not be right for YOU.
Hoping he turns out to be significantly different from what this little bit of info implies. And hoping this wedding you are attending has some cute single wedding crashers.
