why was matt agoraphobic

http://en.wikipedia.org/wiki/Agoraphobia#Causes_and_contributing_factors

I think it was because of his parent's car accident.

You're Merlin, the happy pig!

At one point he said that he didn't like to go out because of "filthy streets and criminals round every corner"

Matt grew up in Herne Bay and it would seem had a very sheltered, strict upbringing; remember him and Martin having a conversation about Matt's father shouting at Matt, hitting him, once even scaring Martin so much he pissed his pants (he always was pathetic tosser)?

It may be safe to assume they all ended up in that flat after moving to London as students and then Matt's parents were both killed in a car crash, I guess leaving him an inheritance. There's never any mention of any other siblings (apart from when Matt makes up his Royal Marine hero brother "Danny") so my guess is Matt completed uni or dropped out and then began living his agoraphobic existence a year before series 1 began.




What if everyone started telling the truth?

He's suffering from the loss of his parents and now finds the outside world frightening and dangerous.

Though I'm not sure why it was triggered later on in life, I think that's left up in the air.

I have the DVDs but I'm going from memory here. I'm certain it's revealed Matt was a kid and having dinner at Martin's house when his parents died. To me this is perhaps a reason why Matt treats Martin badly as he's the reason he wasn't with his parents.

Everyone else seems to have focused on his parents, so I'll make a different suggestion... I used to house-sit for my mother every so often, and she'd provide two weeks' worth of food (kind of as payment), so I basically never had to leave the house during that time, and more than once I noticed that when I finally had to go out somewhere after not being outside or speaking to anyone for like 10 days, it'd make me anxious and once I actually had a panic attack when I went out, and ended up just going back home. So maybe, once he started getting money from flatmates and never HAD to go anywhere, that started to snowball into agoraphobia, where the more he's scared the more he stays in, which makes his agoraphobia worse, and so on. That first instance of anxiety, where it's the deciding factor between leaving the house and staying in, was probably small and casual, and maybe wouldn't have stopped him if he HAD to go out, but coupled with the fact he didn't have to, and that he basically had a runner to get all his groceries and stuff, it could be enough to start him on the path to being an agoraphobic. Sure, it's fiction, and I'm basically speculating on backstory that doesn't exist, but whatever.

He was agoraphobic cos his parents died in a car crash

Bloody hell, who knew Dave ja vu was 12 years old.