Myth: Marijuana Prohibition Improves Public Safety

There is no evidence that the prohibition of marijuana reduces the net social risk of accidents. On the contrary, recent studies suggest that marijuana may actually be beneficial in that it substitutes for alcohol and other, more dangerous drugs. Research by Karyn Model found that states with marijuana decrim had lower overall drug abuse rates than others; another study by Frank Chaloupka found decrim states have lower accident rates too[17] In Alaska, accident rates held constant or declined following the legalization of personal use of marijuana[18] In Holland, authorities believe that cannabis has contributed to an overall decline in opiate abuse. Recent government statistics showed that the highest rates of cocaine abuse in the West were in Nevada and Arizona, the states with the toughest marijuana laws.

Myth: Drug Urinalysis Improves Workplace Safety

There has never been a single, controlled scientific study showing drug urinalysis improves workplace safety. Claims that drug testing works are based on dubious anecdotal reports or the mere observation of a declining rate of drug positives in the working population, which has nothing to do with job performance. Such scientific studies as have been conducted have found little difference between the performance of drug-urine-positive workers and others. The largest survey to date, covering 4,396 postal workers nationwide, found no difference in accident records between workers who tested positive on pre-employment drug screens and those who did not[19] The study did find that drug-positive workers had a 50% higher rate of absenteeism and dismissals; put another way, however, drug users had a 93.4% attendance record (versus 95.8% for non-users) and fully 85% kept their jobs for a year (versus 89.5% for non-users)! An economic analysis of postal workers in Boston concluded that the net savings of drug testing were marginal, and that there could be many situations where it is not cost-effective[20] Another survey of health workers in Georgia found no difference in job performance between drug-positive and drug-negative workers[21]

Myth: Random Urinalysis is Needed in Safety-Sensitive Transportation Jobs

Government rules mandating random drug testing were promulgated without any prior statistical evidence that illicit drugs constituted an inordinate safety hazard. Not a single commercial passenger airline accident has ever been attributed to marijuana (or, for that matter, alcohol) abuse[22] Drug tests on rail workers found no elevated incidence of drug use among workers involved in accidents[23]

Random drug testing of transportation workers was enacted as a hysterical reaction to a single 1987 train collision, in which 16 Amtrak passengers were killed by a Conrail train that failed to stop. The engineer and brakeman of the Conrail train at fault were found to have recently smoked marijuana, though it was never firmly proven that marijuana caused the accident. The Conrail engineer had an extensive record of speeding and drunken driving offenses and was known by management to have drinking problems. Critical safety equipment that would have averted the accident was missing or disabled. A subsequent investigation by the National Transportation Safety Board recommended that Conrail improve both its management and equipment, but did not recommend random testing. Nonetheless, Congress responded by mandating random drug testing on the entire transportation industry, from airline flight attendants to gas pipeline workers.

Myth: A Single Joint Has Effects That Linger for Days and Weeks

While it is true that THC and other cannabinoids are fat-soluble and linger in the body for prolonged periods, they do not normally affect behavior beyond a few hours except in chronic users. Most impairment studies have found that the adverse effects of acute marijuana use wear off in 2-6 hours, commonly faster than alcohol[24] The one notable exception was a pair of flight simulator studies by Leirer, Yesavage, and Morrow, which reported effects on flight simulator performance up to 24 hours later[25] The differences, described by Leirer as "very subtle" and "very marginal," were less than those due to pilot age. Another flight simulator study by the same group failed to find any effects beyond 4 hours[26] Similar "hangover" effects have been noted for alcohol[27]

Chronic users may experience more prolonged effects due to a build-up of cannabinoids in the tissues. Some heavy users have reported feeling effects weeks or even months after stopping. However, there is no evidence that these are detrimental to safety.

References on Accidents and Drug Testing: Alcohol, Drugs and Driving: Abstracts and Reviews Vol. 2 #3-4 (Brain Information Service, UCLA 1986); Dale Gieringer, "Marijuana, Driving, and Accident Safety," Journal of Psychoactive Drugs 20 (1): 93-101 (Jan.-Mar 1988); Dr. John Morgan, "Impaired Statistics and the Unimpaired Worker," Drug Policy Letter 1(2): May/June 1989, and "The 'scientific' justification for drug urine testing," The University of Kansas Law Review 36: 683-97 (1988); John Horgan, "Test Negative: A look at the evidence justifying illicit-drug tests," Scientific American, March 1990 pp. 18-22, and "Postal Mortem," Scientific American, Feb. 1991 pp. 22-3; Dale Gieringer, "Urinalysis or Uromancy?" in Strategies for Change: New Directions in Drug Policy (Drug Policy Foundation, 1992).

Myth: Pot is Ten Times More Potent and Dangerous Now Than in the Sixties

The notion that pot has increased dramatically in potency is a DEA myth based on biased government data, as shown in a recent NORML report by Dr. John Morgan[28] Samples of pot from the early '70s came from stale, low-potency Mexican "kilobricks" left in police lockers, whose potency had deteriorated to sub-smokable levels of less than 0.5%. These were compared to later samples of decent-quality domestic marijuana, making it appear that potency had skyrocketed. A careful examination of the government's data show that average marijuana potency increased modestly by a factor of two or so during the seventies, and has been more or less constant ever since.

In fact, there is nothing new about high-potency pot. During the sixties, it was available in premium varieties such as Acapulco Gold, Panama Red, etc. , as well as in the form of hashish and hash oil, which were every bit as strong as today's sinsemilla, but were ignored in government potency statistics. While the average potency of domestic pot did increase with the development of sinsemilla in the seventies, the range of potencies available has remained virtually unchanged since the last century, when extremely potent tonics were sold over the counter in pharmacies. In Holland, high-powered hashish and sinsemilla are currently sold in coffee shops with no evident problems.

Contrary to popular myth, greater potency is not necessarily more dangerous, due to the fact that users tend to adjust (or "self-titrate") their dose according to potency. Thus, good quality sinsemilla is actually healthier for the lungs because it reduces the amount of smoke one needs to inhale to get high. 

Myth: Pot Kills Brain Cells

Government experts now admit that pot doesn't kill brain cells[29] This myth came from a handful of animal experiments in which structural changes (not actual cell death, as is often alleged) were observed in brain cells of animals exposed to high doses of pot. Many critics still cite the notorious monkey studies of Dr. Robert G. Heath, which purported to find brain damage in three monkeys that had been heavily dosed with cannabis[30] This work was never replicated and has since been discredited by a pair of better controlled, much larger monkey studies, one by Dr. William Slikker of the National Center for Toxicological Researc[31] and the other by Charles Rebert and Gordon Pryor of SRI International[32] Neither found any evidence of physical alteration in the brains of monkeys exposed to daily doses of pot for up to a year. Human studies of heavy users in Jamaica and Costa Rica found no evidence of abnormalities in brain physiology[33] A 15-year study of 1,318 chronic marijuana users by Johns Hopkins University found no evidence of long-term decline in mental function[34] Even though pot does not appear to cause permanent brain damage, users should be aware that persistent deficits in short-term memory have been noted in chronic, heavy marijuana smokers after 6 to 12 weeks of abstinence[35] It is worth noting that other drugs, including alcohol, are known to cause brain damage.