Any causal differences on participants between heroic versus evil campaigns?

If there are found to be causal changes to those who participant in role-playing games, are there any differences in the effects on participants if they participate in "heroic" versus "evil" campaigns? My experience with running (and rarely playing) evil campaigns, is that they are not sustainable. Event the cleverest ones only last about half a year before they've made enough enemies that survival becomes very problematic.

Since catharsis is now being significantly ruled as an invalid theory by the studies of the last few decades, does this mean that the "cathartic effect" of playing an evil character is actually reinforcing negative behaviors that would translate into negative thoughts and behaviors in "real life"? Or does it actually allow safe experimenting and "venting" in a safe environment?