Jewish World Review Jan. 24, 2003 / 21 Shevat, 5763

Marijuana: A Gateway Drug?

By Robert A. Wascher, M.D., F.A.C.S. | There has been a great deal of debate regarding the impact of marijuana use on the subsequent use of other illicit drugs. Those who believe that marijuana serves as a "gateway" to the use of "harder drugs" often cite limited scientific evidence suggesting that most hard drug users began with marijuana before graduating to other substances.

On the other side, there is evidence suggesting, albeit often anecdotally, that the majority of occasional cannabis users do not go on to use other "hard drugs." Unfortunately, there has not been a lot of hard scientific evidence to support either camp's position, although previous studies have appeared to show, variously, that genetic or environmental factors might play a role in a predisposition to graduate from marijuana to other substances.

The current issue of the Journal of the American Medical Association contains an interesting Australian study that attempts to resolve this controversy. The study enrolled 300 pairs of same-sex twins, both identical and fraternal, with an average age of 30 years. The twin-pairs were surveyed between 1996 and 2000, with each pair of twins consisting of one person who began smoking marijuana prior to age 17, and a second twin who abstained. The study looked at the use of nonprescribed sedatives, hallucinogens, cocaine and other stimulants, and opiate narcotics. Alcohol dependency and cannabis use were also assessed.

The study determined that individuals who began using marijuana before age 17 had 2 to 5 times the risk of subsequent progression to other drugs, as well as to alcohol dependency, when compared to their twin siblings who did not use marijuana. When the researchers corrected their results for other potentially contributing factors (e.g., early-onset alcohol or tobacco dependency, parental conflict or separation, childhood sexual abuse, and psychiatric disorders), there was no significant change in their original findings.

There was also no significant difference in the results between identical and nonidentical twin-pairs. The authors, therefore, concluded that the early onset of marijuana use (before age 17 in this study) was associated with a 2 to 5 times risk of progression to the use of other illicit substances, and to alcohol dependency.

The use of same-sex twins in this study was designed to eliminate potential genetic or environmental variables that might have had an impact on the results of the study. While these results do not provide a precise explanation for the observed "gateway effect" associated with early-onset marijuana use, it may be that peer pressure and social pressures associated with marijuana use leads to a reduced threshold for experimentation with other illicit substances and alcohol (as well as easier access to these non-cannabis drugs from cannabis dealers).

Ironically, the current legal status of marijuana may also be an important factor, as cannabis use is proscribed by law, making its use a criminal act.

Having breached this legal threshold, there may be fewer reservations regarding the subsequent use of other illicit substances. It would, therefore, be interesting to see a similarly designed study of the impact of early tobacco and alcohol use (both are legal psychoactive drugs) on subsequent illicit substance abuse.

While there may well be certain genetic and environmental factors that predispose to substance abuse in some cases, the contribution of marijuana's current legal status to both its initial use, and to the subsequent progression to use of other drugs, has not yet been studied. Whether you take a libertarian view or a conservative view of substance abuse, and the laws that regulate the use of all psychoactive substances (including tobacco and alcohol), this study raises as many questions as it appears to answer.


Over the past two years, I have reported on a number of epidemiologic studies that have confirmed a pandemic of obesity among both adults and children in the United States. Our society's unprecedented girth and heft have been largely (no pun intended)... attributed to our penchant for fatty calorie-rich diets, and an aversion to physical activity, which has been abetted by a bevy of effort-reducing "convenience devices."

Our fast food culture has made it possible to spend less than 10 minutes in a fast food restaurant's drive-thru lane before driving off with a single meal containing, literally, an entire day's supply of fat, protein and calories. We no longer have to stalk, hunt or tediously grow provisions for ourselves and our families. For that matter, we don't even have to walk to or from our cars, as many restaurants now deliver prepared food to our front doorsteps.

I often like to observe people when I am out and about. I never cease to be amazed at the degree of aversion many people have to even the most modest expenditure of effort in their daily lives. One especially poignant example of this phenomenon is the behavior that I like to call the "20 steps (or less) parking plan."

Surely you have seen this same behavior yourself while trying to find a parking space at a large shopping mall. Many people will drive round and round the parking lot, endlessly searching for that elusive parking spot that is within 20 paces of the mall's entrance. They lurch from lane to lane, scanning the rows of cars for an empty space, or for signs of another car's incipient departure. They verbally accost you when you are walking by, asking if you are about to leave.

However, once you have passed beyond the critical 20 pace threshold, the drive-by interrogations rapidly thin out. Meanwhile, dueling motorists frantically attempt to simultaneously maneuver their vehicles into a single coveted empty space within the "20 paces zone," their faces screwed into expressions of anger and frustration.

Occasionally, they will indulge in acts of "mutually assured exclusion," each preventing the other from gaining access to the prized parking space as if they were hunger-crazed beetles fighting for some prized bit of detritus. Overeating and underexercising have become the American Way of Life for many of us overworking undersleeping overstressed citizens, and our burgeoning waistlines testify to the consequences of such a lifestyle. An intriguing study, also published in the current issue of the Journal of the American Medical Association takes a look at the patterns and trends in food portion sizes in the United States between 1977 and 1996. More than 63,000 individuals, aged 2 years and older, were surveyed regarding their eating habits during the period of study.

The surveys inquired about specific food items consumed, as well as portion size and the locations where each meal was consumed. The study determined that portions sizes varied according to the location of each meal. Not surprisingly, the largest portions of food were consumed at fast food eateries and at home, while the smallest (though still quite substantial) portions were consumed at sit-down restaurants.

Between 1977 and 1996, food portion sizes increased for meals eaten both inside and outside of the home. Oddly enough, the consumption of pizza, among the various specific food items tracked by this study, did not increase in terms of portion size between 1977 and 1996. However, energy intake from food, based upon portion size, significantly increased during the period of study for salty snacks, soft drinks, hamburgers (my own personal weakness), french fries, and Mexican food (another of my own personal weaknesses).

This study is one of very few studies that have actually quantified the inexorable upsizing of food portions over the past 20 years in our country, as well as identifying the locations where most of this super-sizing is occurring. The overabundance of inexpensive calorie-dense foods in our culture provides a temptation that caters to our genetic predisposition to energy hoarding. Unfortunately, we expend almost no calories while circling endlessly in the parking lot in search of the parking space that puts us as close to the mall's front door as possible.

Eat less, exercise more.


Don't ask me who originally came up with the idea for this study, but the current issue of the Archives of Dermatology has published a study looking at the effects of Botulinum toxin (Bo-tox, for you Hollywood types) on body order. However, to be fair, Bo-tox has been used, experimentally, to treat a condition referred to as hyperhidrosis. People with hyperhidrosis experience excessive sweating (usually in the armpit and groin areas), which is, needless to say, often accompanied by an increase in body odor. In this small study, 16 volunteers had one of their armpits injected with Bo-tox, and the other armpit injected with plain salt solution (placebo).

Neither the patient nor the person administering the injections knew which armpit got the Bo-tox and which pit got the saline solution. After a period of 7 days, body odor was assessed, and I am not making this up, by a "T-shirt sniff test." The authors found that the armpit area on side of the T-shirt that was treated with Bo-tox was significantly less smelly, and that the quality of the odor on the treated side was less unpleasant, when compared with the side of the placebo injection.

While I cannot say who made the greater sacrifice for science by participating in this study (i.e., the people who let someone inject Bo-tox and saline into their armpits, or the "T-shirt sniff test" sniffers), it is nonetheless reassuring to witness the march of science towards the eventual eradication of both life-threatening diseases and offensive body odor. So, don't be surprised if the host of that next Bo-tox Party that you attend asks you to raise your arms and close your eyes.

(Remember, you read about this first at JWR!)

JWR contributor Dr. Robert A. Wascher is a senior research fellow in molecular & surgical oncology at the John Wayne Cancer Institute in Santa Monica, CA. Comment by clicking here.


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© 2002, Dr. Robert A. Wascher