Proponents of legalizing marijuana claim that the drug is different from other street drugs. One difference claimed by users is that marijuana is not habit-forming in the same way as are alcohol, tobacco or cocaine. Studies do show, however, that marijuana use involves the very same regions of the brain as are stimulated by other addictions. Addictions to substances or behaviors (such as pornography or gambling) all involve habituated triggers to brain activity. It seems reasonable then to assume that if one can prove similar triggers within the brain relating to marijuana use that a case can be made for its addictive quality.
Marijuana use is admittedly difficult to test on laboratory mice since it is not a substance which they can easily self-administer. Other substances are often added to a lab animal’s water supply making consumption rates simple to measure and quantify. In this case, a researcher from New Mexico needed to find another way to compare marijuana use with other addictive drugs and behaviors. By taking functional magnetic resonance imaging (fMRI) scans of subjects who were confirmed marijuana users, the scientist was able to compare brain activity associated with addiction. The study recruited 38 participants, all of whom were self-reported marijuana users, and asked them to suspend use for three days.
During testing, participants were given visual cues, some associated with marijuana use (a pipe, for example) and some not. As subjects viewed each clue their brains were monitored for activity/responses. Interestingly, when the marijuana pipe visual appeared user’s brains showed activity in the same reward regions most associated with addiction. Whether a person is addicted to smoking, gambling, drugs or something else, – the reward area of the brain becomes stimulated by the promise of the substance or behavior. The same proved true with marijuana.
The study also used questionnaires to determine how much marijuana use impacted the participants’ daily lives. The survey is a standard tool and is referred to as the problem scale for marijuana use. There was a definite correlation between the score on the questionnaire and the person’s fMRI results. Participants with higher problem scores also showed greater activity during fMRI testing. In effect, the fMRI scan reflected the extent of the person’s marijuana use.
So, the question of whether or not marijuana is an addictive substance seems to not really be in question after all. However, those in favor of making marijuana a legal substance may still argue that it is not as strongly addictive as things like tobacco, cocaine or alcohol. This study did not answer the question of relative intensity. It merely demonstrated that marijuana is an addictive substance and produces the same physiological responses as do other addictive drugs and behaviors. On that score, marijuana stands arm in arm with every other addiction.