Marijuana contains 421 different identified compounds.  Yet "the heat produced by smoking [it] causes chemical changes that increase this number to more than 2,000," including sixty-one different lipid-soluble cannabinoids (Liska, 48).  Many of these chemicals are psychoactive, and remain largely unstudied.  In addition, the concentration of these chemicals vary greatly from plant to plant, and exist in uncontrolled amounts.

    The most commonly referred to compounds (and the most widely studied ones) are the tetrahydrocannbinols, which include, most notably, delta-9-tetrahydrocannbinol or THC.  In fact, it is responsible for eliciting marijuana's pharmacological effects, and the concentration of THC determines a drug's strength.  For instance, "a typical joint contains between .5 and 1.0 grams of cannabis plant matter, which varies in THC content between 5 and 150 milligrams.  Most ordinary marijuana has an average of 3% THC" (NIDA Notes, 1).

    Nevertheless, in addition to varying with each dose, "the pharmacological effects of delta-9-THC vary [according to the] route of administration, experience of the user, vulnerability to psychoactive effects, and setting of use" (Goodman and Gilman, 572).
 

    Shortly after smoking, the user experiences a relaxing sensation, and becomes increasingly aware of sights and sounds, which they focus on with intensity.  In fact, this focus often eclipses an awareness of their environment, and the users have a delayed rate of response.  In addition, users experience giddiness, dryness of the mouth (or "cotton mouth"), and hunger (or "the munchies").

    While most of the effects of marijuana and the experienced "high" wear off after about two hours, some effects can be more lasting.  Yet the extent to which these effects exist is highly debated.  For instance, one group of researchers noted that since the "use of marijuana affects the parts of the brain that control memory, attention, and learning," heavy or daily use can result in impaired functioning of those parts (Fletcher, Page, 1056).  This includes short-term memory loss, a decline in the ability to perform multiple tasks and the ability to recall information.  Yet, as mentioned earlier, these consequences are dose dependent.  Despite evidence that marijuana has long-term cognitive effects, almost all pro-decriminalization groups will argue otherwise. 

     In addition, a heated debate exists over marijuana is addictive or not.  One study found that chronic users "experience significant increases in anxiety, irritability, physical tension, and physical symptoms and decreases in mood and appetite during marijuana withdrawal.  These symptoms were most pronounced during the initial 10 days of abstinence, but some were present for the entire 28-day withdrawal period" (Kouri and Pope, 492).  Although these findings support the notion of a marijuana withdrawal syndrome in humans, other studies suggest otherwise and the debate continues.