[danbmil99]

There are most definitely "bad trips" which can be deeply frightening, scarring experiences. The worst effects though seem to come to those who become somewhat psychologically addicted to the thrill of the experience, and take repeated doses every few days or weeks over a period of years.

The closest analogy I can make is to PTSD; they have trouble dealing with the banality and slow pace of normal life, and seem somehow "burnt out" (cliche, but a very apt term for someone who took one trip too many.)