Cannabis and DXM happen to be Monkey's absolute favorite drug combination.
From Monkey's experience, DXM and cannabis both potentiate each other. SWIY's negative experience underscores the fact that marijuana is a serious drug in its own right. The problem is that most people don't give it enough respect. Using cannabis to potentiate a DXM high, isn't the same, for example, as potentiating an opiate high with cimetidine, grapefruit juice, etc. DXM and weed have an incredible, complex synergy, according to Monkey.
It appears to Monkey as if the cannabis was strongly potentiated by the DXM in this instance, not the other way around. If Monkey were out of his skull, tripping on DXM alone, he doubts that the negative environmental factor of a police car would have any impact on his trip. He would dissociate from the experience.
For that matter, Monkey is an experienced user of weed, and finds it unlikely that cannabis would trigger such a bad DXM trip for him, at normal doses. When Monkey first started smoking, however, it would have been quite possible for paranoia to take control.
According to Monkey, psychological factors seem to be as important as the actual physical effects of drugs on one's brain, whether cannabis, DXM, alcohol, what have you. This becomes less predictable when combining substances. Monkey disagrees with Graduasic that a bad DXM trip, not combined with other drugs, is impossible. He thinks panic could easily result from someone taking more DXM than they are psychologically ready to handle. He couldn't imagine going to the third plateau on his first DXM trip.
In Swims experience, bad trips have usually been caused by weed when paired with shrooms. the problem is that the shrooms are usually already affecting him and so he doesnt realize how much he's smoking. he gets too high and the combination begins a spiral of paranoia coupled with irrational thinking. he knows now that its not the shrooms alone for two reasons. one, during a trip bad thoughts only ever start entering his mind when he starts smoking, and two, he has gotten too high before, and it leads to a toned down version of a bad trip in which the difference is his ability to rationalize what he's feeling.
for this reason swim believes that on any substance one must be acutely aware of the fact that weed is not just an enhancer, and that too much will almost certainly lead to a bad trip due to the paranoia inducing effects in combination with the severely fucked up state (to put it bluntly) that one is in. A suggestion from swims personal experience is this, if you try the drug with weed and you have a bad trip, try it again without weed and see what happens. chances are you'll have a decent trip, or at least be able to stop a bad trip when it starts. also, if you fail to grasp or refuse to believe that weed should be taken seriously, then without taking anything else, smoke as much weed as you possibly can at least once in your life just to get a feel of the awesome power that it has. swim knows that this kind of experience gave him a new respect for it.