1. An Overview of

Suddenly you're through the looking glass. It's your bedroom or living room all right, and everything is exactly the same, but everything is exactly different than it ever was before you were stoned. And suddenly you don't care about your arthritis, or that you have to appear in court the next day because of a speeding ticket, or that you've got a mid-term paper due in two days, or that you've only got one ear.

— A Child's Garden of Grass [1]

General Effects

Only two effects of marijuana on the human body have been established without question: a reddening of the eyes (conjunctival vascular congestion) and a temporary increase in the rate of heartbeat (tachycardia) Marijuana also appears to dry up the mouth and the tear ducts.[2]
    Although marijuana is not new to American life, and although its recorded history goes back several thousand years, it was not until 1968 that these basic facts were established. In a study conducted at Boston University, Dr. Norman E. Zinberg of the Harvard Medical School and Andrew Weil, then a medical student at the same institution, conducted a series of pilot experiments in an effort to learn about the effects of marijuana intoxication on human beings.[3] What made the experiments notable was that this was the first study of cannabis to be conducted in a double-blind fashion, with neither the subjects nor the administrators of the experiments aware during the study of who was smoking marijuana and who was smoking a well-designed placebo.
    Among other findings, the Zinberg and Weil study disproved the commonly held notion that marijuana causes a dilation of the pupils This "fact" had been so prominently believed by the general public that it was often used by the police as a cause for searching a residence for illicit drugs. Some drugs do cause a dilation of the pupils, but marijuana Is not one of them. This basic error is typical of the state of marijuana "research" until the 1960s, before which, apparently, nobody had thought to study the drug scientifically. The misconception about dilated pupils arose in the first place, Zinberg and Weil speculated, because smokers were using marijuana in darkened rooms; that, and not the drug, accounted for the change.
    Subsequent studies and surveys have revealed other basic effects of marijuana.[4] Users commonly report an increased ability to concentrate on whatever it is they are doing or thinking about; for many, marijuana leads to a general increase in the intensity of most aspects of life. Another very common effect is a heightening of sensual excitation: listening to music, viewing a film or work of art, making love, eating—all are commonly reported to be enhanced by marijuana. Often, when a user is high, one of his senses will work cooperatively with another in a process known as synesthesia: for example, a smoker may have the sensation of being able to "see" the music he is listening to. In addition, many users find that abstract ideas and sensations become more concrete, and more visual as well.
    Under the influence of marijuana, time appears to pass more slowly, short-term memory seems to be impaired, and smokers often find themselves feeling relaxed, free, creative, and outside the normal restraints of time, space, and, sometimes, social amenities. Users speak of a sense of "well-being" and commonly feel peaceful and content. They tend to feel happy, as well. "When I'm high," says a day-care worker, "my mouth starts to hurt from smiling so much."
    The high normally reaches its peak within about half an hour after smoking; after another hour, it often gives way to a slight lethargy or tiredness. Conversation and general awareness, after being stimulated during the first hour, will often fade a little in the second. This process is known as "coming down," and for some smokers it is slightly unpleasant, resulting in a headache or in a "cloudy" or "foggy" mental state. The effects of coming down may be delayed by a second or third round of smoking or by going to sleep. The most common aftereffect is tiredness, which, for a few smokers, extends into a kind of hangover the following day. Although different kinds of marijuana appear to have somewhat different effects, the determining factors reside in the individual rather than in the drug.
    Marijuana's most common effects occur in the mind of the user. Ideas may flow more quickly ("like throwing gasoline on a fire," observes a scientist), and the smoker may find himself thinking more imaginatively and perhaps gaining a new perspective on a familiar scene or problem. The new perspective sometimes renders events transcendent; at other times, it illuminates the mundane; occasionally, the user may have trouble knowing the difference.
    There are physical effects as well, and smokers sometimes talk of such responses as a tingling sensation in their limbs, a drop in body temperature, and various other subtle changes. But it is not clear whether these changes are real or merely imagined As sociologist Howard Becker explains it, "There are all kinds of physical and even psychological events going on in your body all the time. Most of them you've learned to ignore, like momentary tics of a muscle, or quivers, or other things of that kind. Ordinarily, you feel it happening and you say, 'Oh, that.' When you're a child, you tell your mother and she tells you not to worry about it. And the next time it happens, you ignore it. On marijuana, however, you might not ignore it, especially if you're nervous about using the drug. But if you just sit and pay serious attention to your body for a few minutes, whether or not you're stoned, you'll discover all sorts of things going on, things you would normally ignore, things which are capable of being interpreted if you're so inclined."
    Many smokers speak of an increased awareness of their bodies in positive terms. "I can almost feel the blood rushing through my veins," says one man, "and the boom boom boom of my heart."