You won't die if you take medication for a diagnosable disorder. Chances are Anna Nicole's son died because he was these drugs to get high. He died from a lethal combination of zoloft, lexapro, and methadone. Methadone is commonly abused by people coming off of heroin. So, he probably was trying to get high, and the high dosages killed him.
I have PTSD. I have a lot of anxiety attacks and depression, too. I'm also on medication for this. One of the meds I take is the same med Anna's son was taking (zoloft). Taking these drugs won't kill you; unless you take too much or you're taking the meds improperly.
I think people use the extreme cases as an excuse to not be treated for their disorders and it's kind of dumb. Why suffer when you can be treated and a lead a productive life?