Oh dear, I was a card carrying member of NORML for years. I also worked in a pharmaceutical research laboratory where we were conducting extensive research on various drugs and their affect on human behavior and brain chemistry. I had access to restricted Government and private research reports and data on Marijuana (I cannot disclose specific data). <If you do not enjoy my comprehensive posts stop reading now.>
Marijuana is in fact considered a hallucinogen and a barbiturate (due to its effects rather than its actual chemical composition). The THC content largely determines its hallucinogenic effect, but the most powerful marijuana doesn't even compare to weakest concentrations of LSD-25 or mescalin. Marijuana, unlike almost every other drug is a victim of a property implied by one of its names, "weed". It can grow almost anywhere and can flower several times a year in a wide variety of soils and climates. It is one of the few vegetable based narcotics that can be grown casually by private citizens in sizeable quantities. As Skyrock pointed out, Marijuana criminalization was used as a tool to further politically motivated restrictive government immigration and deportation policies against Hispanics. Later enforcement, especially in the deep south and inner cities, used marijuana criminalization to target African-Americans.
There is proof that like cigarettes, raw, unprocessed Marijuana vegetable matter contains carcinogens, free radicals and tar. But, 75% of smoked marijuana is unfiltered, unlike cigarettes. If commercially produced in the same fashion as cigarettes but without all the extra chemicals tobacco companies add to their products, it would be a much lesser source of cancer causing agents. There is some very strong evidence that Marijuana use does temporarily deleteriously effect short-term memory, cognitive reasoning and fine motor control, much like alcohol use. However, unlike alcohol, other than simply the fact that you are smoking unprocessed, unfiltered vegetable matter, the active ingredients have no permanent adverse affects on any organ or system in the human body. Marijuana is not a poison like alcohol which is the reason there is no "hang-over".
From a behavioral perspective Marijuana and alcohol have much less in common. Alcohol's "intoxicating" effect is mostly a result of the altering of a brain region called the reticular formation. This part of the brain is responsible (among other things) for filtering sensory input. It throws out sensory information it deems "unimportant" only allowing the important stuff to pass though it to other parts of the brain. For example, I am wearing socks right now, but unless I choose to focus my attention on them my reticular formation filters out the "feel" of them on my feet and ankles. So, if the reticular formation is a filter allowing only important sensory input to pass through, alcohol clogs the filter. More and more sensory input is discarded as irrelevant in proportion to the level of alcohol in the blood to the point where the user passes out in blackout fashion. During the latter phases of acute alcohol intoxication no sensory input is recorded at all in the memory as it has all been discarded. I am sure no one needs any explanation or examples of how dangerous that could be in many situations.
Marijuana, although it's a lot harder to isolate particular brain regions affected, has almost the entirely opposite effect. Marijuana actually increases both the acuity of the senses and the actions of them, in terms of associations derived by their interpretation, in the brain. To put this another way, it creates a connectedness between sensory perception, memory and cognitive thought that expands awareness of the single object of attention in a multifaceted way incorporating both left and right hemispheres. The problem with this, and why marijuana intoxication is dangerous to operate a motor vehicle on, is because this increased brain activity focused upon a single object of attention takes away from "peripheral" awareness of everything else around you. Your situational awareness, as it were, is reduced to the point of nonexistence as you can focus extremely intently but on only one object at a time.
The other necessary comparison between alcohol and marijuana is its affect on the emotional state or mood. Both, have an euphoric effect, but the euphoria of alcohol is relatively short-lived compared to the length and extent of intoxication. After a certain point the euphoria wears off and the misinterpretation of improperly filtered information allows for extreme, if not violent, expressions of uninhibited emotional behavior. As intoxication wears off the lower alcohol level in the blood stream in the brain depresses mood creating an anti-euphoria state further exacerbating wavering emotional stability.
Marijuana has a much longer lasting Euphoric period. It can be as long as the intoxicated feeling itself and is rarely associated with a "crashing" of mood as the level of THC affecting the brain subsides. Rather than information being over-filtered, marijuana actually deepens the interpretation of information increasing its impact on emotions. This is why a funny joke on marijuana is hilarious to the point a wetting oneself, whereas normally it would just be worth a chuckle. This is true of any interpretation, a sad movie while intoxicated by marijuana may make a grown man weep openly when he would not otherwise shed a tear. So, it is far less likely for someone intoxicated by marijuana to display negative emotions or violence as the experience of profound empathy has the opposite effect of alcohol induced sensory distortion and misinterpretation.
There was a recent study done by British researchers that indicated marijuana if used habitually by those with psychiatric problems could increase the chance of them becoming acutely symptomatic. It even seemed to indicate that those with no diagnosed psychiatric ailment, but were predisposed in some previously unknown way, were more inclined to manifest that condition after prolonged habitual use. There was no evidence to support the degradation of mental stability in those considered "normal" though. So, I guess from that one could say, based on this research, habitual marijuana use is definitely not going be recommended for everyone, but then again no drug is.
There are many reasons marijuana remains illegal, take it from someone who has read Government reports on the subject, very few of the reasons are specifically in the, "best interests of the citizenry". I will just list some here...
1) Possibly lowers worker productivity, unlike the stimulating effect of nicotine.
2) Is far too easy to grow and cultivate, therefore regulate and tax.
3) Concentrations of the psychoactive substance THC varies widely therefore has unpredictable effects.
4) In its raw form it can cause cancer.
5) It is extremely cheap to produce and process so even if taxed market forces would make it relatively economically insignificant.
6) Govt seizure of private property indirectly associated with marijuana indictments exceeds the street value of the drug seized itself more than 100 fold.
7) Some conclude that anyone who would smoke a joint today would likely shoot up heroin tomorrow...the "Escalating drug use pattern theory".
