Is madness contagious? Is it a disease you can catch from another person? If someone believes in something hard enough will you start to believe in it too?

I juat woke up from this dream...I was running through a forest and Jill's delusion was chasing me. Or rather, not chasing me, because it was just walking, no hurry, because it knew I couldn't get away. It had all the time in the world.
It's not surprising that I dreamed about the Slender Man, after all those blogs I read every day...but I don't like it, all the same. Not just because it was a scary dream, but because there's stil this nagging feeling, no matter how much I try to dismiss it, that this is how it starts. In all the stories, all the videos, it begins with seeing the monster in your dreams. And the fact that this is legitimately bothering me frightens me even more, because that means that I'm taking this a little bit seriously. And now I can't get back to sleep.

When I saw all the men in black suits at Jill's funeral, my heart stopped for a moment. Not because it reminded me of her madness, but I because I had this sudden feeling that one of them would turn around and have no face. I was, if for only a second, faling prey to her hallucination.

I have a confession, and this is something I've never told any of my friends, other than Kevin: I have a history of depression, anxiety, panic attacks, and mild OCD. I actually had to take a leave of absence during high school because I couldn't deal with the stress of it. I used to have panic attacks- full on, crouched in a corner crying and hyperventilating, thinking you're going to die panic attacks. I'm on some anti-anxiety meds these days, and so I'm doing pretty good in general, although every once in a while, in times of stress, I'll have a panic attack again. I almost had one at Jill's funeral, but managed to keep it together.

I don't say this to get pity- in fact, usually I hide my mental illness. It's not a side of myself that I like to show off, and I don't have it as bad as some people. Most of the time it's something I can kind of ignore, but it crops up in places, like how I can't have four of anything at a time, and I have to take pills every morning, and I go to a psychiatrist sometimes. But like I said, Kevin is the only person outside of my family that knows about this, and I'm very close-mouthed about it generally.
The reason I told you this here is that it's a pretty compelling reason for me to be nervous about digging into something that made my friend lose her grip on reality.
But I'm still looking.
And that also makes me nervous.