i think that marijuana, being a mild hallucinogen (but not a psychedelic in any true sense), will produce a trip at very high doses (depending on the individual). HOWEVER, it's nothing like psilocybin or LSD (or even MDMA). When you smoke pot it's like baby steps.. it's kind of a trip but it's not a full trip. With marijuana you get a body high and a sense of euphoria, but not a visual trip with vivid daydream-like hallucinations.

True psychedelics will fuck with your head and put you on a different planet alltogether. Most people won't freak out from smoking alot of pot, but it's likely that you will freak out if you take alot of psychedelics, either repeatedly over a long-term basis or taking a huge amount all at once.