I meant more in the way that Joker is also a clown; DP's clown killin' madness applies.
Deadpool is indeed, to a certain degree, a sociopath. He's insane in the way that his cognitive processes don't work the way they should due to his healing factor keeping his entire body, including his brain, in a constant, unstable state of flux. He's 'silly insane'; his mental instability isn't what makes him dangerous.
I've never heard the full reasoning why Deadpool is insane, I know it has something to do with his healing, but what are the details?
I remember him trying to get wolverine to fight, wolverine said no and told him to get a life, so DP uppercutted Kitty for no reason right in front of Wolverine. It was hella funny.
He didn't just uppercut her... he Shoryuken-ed her. He even yelled it as he did so. "SHORYUKEN!"
Deadpool's insane for the reason I gave above. His entire body is constantly in a state of flux; every molecule in his body is unstable. Since his brain is part of his physical body, it is also affected and thus creates an imbalance in his cognitive processes, making him 'crazy' and something ADD-ish. It also messes with his memory like it does Logan's sometimes. He isn't, however, beyond being serious. He, in fact, tends to get deathly serious at times and occasionally he understands there's something wrong with him.
There's talk of it right now, in fact, in the Cable & Deadpool book. Cable explains to Wade that he cannot help his mind since it's affected by his healing factor - the only way to fix his mental instability is to take it away. However, the very second his regenerative powers are removed, he'll die from cancer. At one point in the book, Wade is afflicted with the techno-organic virus and becomes mentally whole at one point, but shakes it off to save Siryn and Cannonball (or Cannonballs as he calls him).