A seizure that affects both sides of the brain would make someone unconscious. Psychological substances like marijuana frequently make people feel, think, and act in unexpected ways. It is truly rare for this to continue after the drug is out of the system, but much more common for it to re-occur when the same drug is given again. Unpleasant experiences with a drug would be a strong reason not to take it again (even an over the counter cold medicine; certainlly with an illegal controlled substance). Might also mention that regretably, the quality control of street drugs is not very good and amphetamine like substances have been known to be added to marijuana. These can cause stressed reactions like shaking. Also, dissociative drugs (PCP) can make someone feel and act very peculiarly and feel detacted from themselves and reality. These are more dangerous than marijuana and the vast majority of the time, when the effect wears off, the effect is gone.