Understanding Marijuana: A New Look at the Scientific Evidence

by Mitch Earleywine

Bhang is the dried leaves of the plant, comparab...

People smoke these leaves or combine them with milk and spices to form a drink that is also called bhang. Ganja refers to the sap-carrying tops of female plants in India, but in...

Charas is hashish, the dried resin separated from the flowers and pressed ...

In addition to ganja, bhang, and charas or hashish, hash oil also appears in the illicit drug market.

The oil has the potential to generate huge profits because it is relatively compact and easy to smuggle. It is often more potent than hashish or cannabis, too.

Dronabinol (Marinol), a synthetic version of THC suspended in sesame oil, can treat poor appetite, nausea, and vomiting (e.g., Lefkowtiz et al., 1995).

Hashish typically contains 20% THC, with some estimates as high as 50%. Hash oil can contain up to 70% THC.

Cannabis sativa used for industrial hemp often contains less than 1% THC.

Marijuana with less than 1% THC has the same effects as a placebo (Zimmer & Morgan, 1997).

Thus, hemp products are not psychoactive. No one will grow intoxicated from smoking the various shampoos, soaps, or clothes curre...

Psychoactive strains of marijuana typically contain 2 to 5% THC, but concentrations as high as 22% have b...

No one has ever died from THC poisoning.

Thus, eating cannabis products may have fewer negative consequences than smoking them. Comparisons between these two ways of administering the drug appear next.

Humans inject drugs intramuscularly (into muscles) or intravenously (into veins).

They also inject subcutaneously (under the skin), a process known as “skin popping.”

People snort drugs int...

Some substances can be absorbed sublingually by placing the...

A few drugs can dissolve through the skin in transdermal administration, like the ubiquitous nicotine patch. None of these methods ...

Cannabis has two popular routes of administration: inhalation (smoking) and o...

In addition, researchers have examined intravenous injections of THC and rectal administration via the marijuana suppository. Drug companies have also proposed a deep lung aerosol, a nasal spray, a nasal gel, a...

All these alternative techniques for administering the drug remain relatively rare, but i...

Several factors influence the amount of THC absorbed during smoking. Larger puffs held deeply in the lungs for a long time create the most dramatic effects.

A gram of cannabis might lead to extreme intoxication when smoked but hardly alter subjective experience if eaten after a full meal.

In one study, marijuana-laced brownies led to some effects in 30 minutes, but peak responses did not occur for 2½ to 3½ hours

Eating the drug avoids the obvious throat and mouth irritation and risk for lung problems that accompany smoking.

The period required to eliminate THC from the body should not be confused with the duration of the drug’s psychoactive effects. People stop feeling high long before THC has left their bodies.

Researchers express the time required to metabolize a drug as its half-life—the period required to break the dose down to 50% of its original amount.

Despite all the variability in elimination periods, marijuana does appear to have a longer half-life than some other drugs. For example, nicotine’s half-life is about 2 hours; caffeine’s is 3 to 6 hours

Popular authors often misinterpret THC’s long half-life by frequently implying that intoxication or some sort of residual effect of the drug remains for weeks at a time.

Yet intoxication dissipates in a couple of hours.

The amount of THC released gradually from fat cells does not create any subjective, cognitive, or emotional effects but may register on drug tests. Thus, a person may test positive for cannabis even a week or two after smo...

Drinking enormous quantities of fluids may dilute THC metabolites in the urine and alter the outcome of a test, but these fluids do not actually alter metabolic rate (Coombs & West, 1991).

With all these other receptors ruled out, researchers concluded that cannabis must work via its own site. Investigators soon identified the cannabinoid receptor and mapped its distribution in the brain (Bidaut-Russell, Devane, & Howlett, 1990; Devane, Dysarz, Johnson, Melvin, & Howlett, 1988 Herkenham et al., 1990).

The cannabinoid receptors in the nervous system, which are known as the CB1 type, are quite numerous.

THC clearly creates changes in the dopamine system, as cocaine, amphetamine, nicotine, and alcohol do (Koob & Le Moal, 1997).

The cannabinoids can enhance dopamine’s activation of movement, suggesting that they might help treat Parkinson’s disease (Sanudo-Pena & Walker, 1998).

THC also interferes with acetylcholine, a neurotransmitter involved in memory. The effect on acetylcholine may underlie the memory problems associated with cannabis intoxication.

Figure 6.6. Anandamide. This cannabinoid occurs naturally in the body. It is the first endogenous cannabinoid discovered.

Several endogenous chemicals appear to interact with the cannabinoid receptor.

Marijuana contains more than 400 chemical components; at least 66 of them are cannabinoids unique to the plant. The most prevalent ones include delta-9-THC, cannabinol, and cannabidiol.

THC is not toxic at high doses like alcohol, nicotine, or many other common drugs.

High-potency marijuana may actually minimize risk for lung problems because less is required to achieve desired effects.

Although intoxication rarely lasts more than a few hours, the complete elimination of THC clearly takes at least a few days.

In general, the drug is incapable of creating an overdose.

People who smoke cannabis but not cigarettes have yet to show severe pulmonary problems like lung cancer or emphysema, but milder respiratory problems do appear.

Yet cannabis is essentially nontoxic. No one has ever died of THC poisoning (Iversen, 2000).

Therefore, a lethal dose would actually require smoking 900 joints.

Thus, even the most devoted pothead with marijuana of legendary strength could not stumble upon a fatal overdose. In contrast, alcohol and aspirin poison thousands of people each year (Doweiko, 1999).

A close look at the data reveals that many people with psychological problems smoke marijuana, but it does not cause their disorders.

Yet some people with mental illness may find that the drug aggravates their symptoms.