I am in agreement with Snafu here. Like anything, some people are super sensitive. The primary risk as I understand it would be Serotonin Syndrome. You wouldn't be doing anything that medicine could truly label as dangerous here. Again, if you're doing the crazy Robo-Tripping type shit, you raise the risk.
As one would expect, a lot of the case studies indicate subjects often on multiple, complex-interacting drugs like for instance:
Abilify (Aripiprazol)
Prozac (Fluoxetine)
Antihistamines
Dextromethorphan
Those types of combinations where shit starts getting very difficult to control because of the myriad of different interactions and potential complications.