Straight Dope

The Research on Marijuana Safety

(Part 3 of 4) by Gary Stimeling

Copyright 2005 Psychotropics Cornucopia, Inc. All Rights Reserved.

Pregnancy and Genetic Defects

            The genetic-damage scare of the late 1960s and early 1970s was similar to other marijuana scare stories of the period. A couple of tentative reports([1]) got a lot of media play, were quietly and thoroughly disproved,([2]) and are still touted by suppressionists.

When pregnant females of some (but not all) species of lab rodents are fed enormous amounts of THC during some (but not all) parts of the gestation period, their litters include many stillbirths and genetic defects. However, offspring of some animals heavily smoked while pregnant show these defects when their mothers are fed a protein-deficient diet but seldom when the diet is adequate, so other factors may compound and confound the results.([3]) Drug effects on reproduction are species-specific, so animal studies in this area are of doubtful relevance to humans.([4]) Studies on primates, probably more germane, have shown no reproductive effects,([5]) even when pregnant chimpanzees were given daily megadoses of THC for five months.([6]) In any case, as pharmacologist Leo Hollister has noted, “Virtually every drug that has been studied for dysmorphogenic [birth-defect-causing] effects has been found to have them if the doses are high enough, if enough species were tested, or if treatment is prolonged.”([7])

In general, and in contrast to alcohol, cocaine, and tobacco, no problems from cannabis use during pregnancy have been found in children followed up through the ages of 4 to 6.([8]) One group of investigators reported that newborns of cannabis-using mothers seemed hardier, and found no differences between them and nonexposed infants in health, sleep patterns, or mental function after the first year.([9])

Quite a few researchers have reported adverse effects that have been well publicized, but these differences always have been few, minor, inconsistent from one study to another, and of no known consequence to health.([10]) An often cited link to two rare forms of childhood cancer seems spurious.([11]) One paper that is often referenced as proof that fetal cannabis exposure lowers children’s intelligence actually showed no overall effect on IQ.([12]) Rather, black (but not white) children scored slightly lower on two subscales of the test; one of these scores correlated only to marijuana use in the first trimester, the other only in the second; and neither correlation increased with greater levels of use, so a causal relationship is unlikely. Another study of IQ found no effect from prenatal marijuana.([13])

A report of premature deliveries caused by marijuana found only a clinically insignificant average of 6 days, once the effects of other drugs were factored out.([14]) However, another group found no connection between cannabis and gestational age.([15])

The largest study of perinatal cannabis use, involving 12,000 women, found no differences between babies who had been exposed to it in the womb and those who had not.([16]) One study of Jamaican women who used ganja extensively throughout their pregnancies found no ill effects.([17]) Another in the same country recorded dramatic benefits. Infants born to the marijuana-using mothers did consistently better on tests of alertness, reflexes, calmness, consolability, and cognitive organization than did children born to a group of carefully matched abstaining mothers.([18])

            Two long-term projects have been devoted to testing elementary-school-age children of mothers who’ve used cannabis while pregnant. In the Ottawa Prenatal Prospective Study, Peter A. Fried and colleagues have followed groups of infants through childhood since 1978, administering hundreds of physical and psychological tests to them. Another team has followed 600 children from their mothers’ pregnancies to age 10.([19]) Based largely on evaluations by parents and teachers, both groups claim that prenatal exposure to cannabis comes back to haunt the offspring with delinquency, difficulty concentrating, and problems with executive function—goal-oriented multitasking, sometimes called the rat-race skills. In the Ottawa study, between the ages of 6 and 9, children of heavy pot smokers scored lower on one test of vigilance, which measured the ability to maintain attention during a boring assignment.([20])

However, these results are not nearly as robust as they’ve been made to seem in the press. Fried himself has played up negative findings and ignored the rest,([21]) but occasional negatives and positives are statistically to be expected in such a large number of tests. Cannabis-exposed infants in his sample scored higher than the others on certain measures early in life,([22]) and on the vast majority the two groups have been indistinguishable, including 11 other tests of attention. Even though the total number of testees is large, the number exposed to cannabis in utero is small, only 30 in the later stages of Fried’s research. This also increases the chance of spurious findings. And although parents in the Ottawa study rated the cannabis-exposed kids as having more conduct problems, that finding didn’t hold up when other factors in their lives were taken into account.([23])

But wait, there’s less! If real, the shortfall in executive function may have resulted from other drugs, including pharmaceuticals never considered. As for the attention problems, Fried estimated, at most, an 8-percent effect from all drugs, including alcohol and tobacco,([24]) which are known to have worse effects on the mental performance of offspring than any claimed for marijuana. The differences could also have been inherited or inculcated by similar behavior patterns in the parents. Parent and teacher evaluations of delinquency and attention deficits are themselves controversial. They have to do with submissiveness, which from the viewpoint of authority figures is a virtue but in terms of the individual’s prospects for creative achievement can, in excess, be a grave flaw. The small claimed variance may indicate only a slightly above-average level of alertness, willpower, or resistance to the enforced restraint of school. It would be interesting to compare these children with the offspring of cannabis-using mothers in Jamaica.

            Ancient custom and modern anecdotal evidence assert that cannabis can benefit the mother, and thus indirectly the child, by alleviating morning sickness and promoting an easy birth. The lack of any clear-cut evidence of harm suggests that these uses are warranted, but, based on caution and common sense, regular or heavy use, like taking any unnecessary drugs during pregnancy, is probably unwise.

Debauchery! Self-Abuse! Bebop! Orgies! Hippies! Social Withdrawal! Oversexed Teens! Decadence! Hip-Hop! Moral Decay! Homosexuality! Kicks! Effete Intellectuals! Loco Wetbacks! Unbridled Lust! Impotence! Beatniks! Lowered Sperm Count! Promiscuity! Misfits and Losers! The In Crowd! Free Love! Shrinking Weenies! Juvenile Delinquency! Perversion! Miscegenation! Bohemians! Anarchy! Hopped-Up Niggers! Rape! Depravity! Impotence! Jazz! Sadomasochism! Rock ’n Roll! Apostasy! Lazy Wogs! Breakdown of Society! Punks! Devil Worship! Tits on Bob! And So On…

Propaganda is the tyrant’s mirror. It shows what the powerful secretly envy or fear they resemble. Suppressionists have blamed every one of these real or imagined cultural phenomena on marijuana.

            In the lurid scare campaign leading up to prohibition, cannabis was said to draw people down into a vortex of unmentionable passion. Sadly, doctors compiling the LaGuardia Report([25]) found no evidence for this. After a scientific hiatus from about 1940 to 1970, the familiar pattern was repeated: New scares were trumpeted, follow-up disproofs were ignored, and discredited claims are still quoted.

Two doctors reported gynecomastia (male breast growth) in three men who smoked weed.([26]) Gynecomastia occurs no more often in cannabis users than other men.([27]) Marijuana does not increase levels of female hormones in men, even in large doses.([28])

Soon afterward, a research group under Robert Kolodny reported that marijuana lowered testosterone levels after smoking, and that chronic users had chronically low testosterone levels and low sperm counts.([29]) Media commentators had few worries about the lack of sexual desire that male hormone deficiency would produce in both sexes. Even large quantities of cannabis have no direct effect on short-term([30]) or long-term([31]) testosterone levels.

Because sea urchins produce large sperm cells, they are often used in research. Lacing sea urchin and bull sperm with THC decreases their motility.([32]) Giving male mice the THC equivalent of 19 joints a day doubles their output of abnormal sperm,([33]) but no one has found convincing evidence that ganja contributes to male or female infertility in humans.([34]) The closest anyone has come is a finding by Nahas’s group that 8 joints a day for a month lowered sperm count and motility toward the low end of the normal range, but the values returned to baseline when the smoking spree ended.([35]) In fact, one team reported that marijuana-smoking women conceived more readily than abstainers,([36]) but this result probably reflects the herb’s enhancement of sexual pleasure rather than a direct effect on fertility.

After giving women marijuana in the lab, one research team found that prolactin levels decreased in some of the women for a few hours, but never below the normal range.([37]) Another group found elevated testosterone levels in a few women.([38]) These studies have been considered proof that cannabis masculinizes women, but when larger numbers are tested, marijuana has no consistent effect on any of the female hormones, even with heavy intake.([39])

By megadosing animals with THC, scientists have succeeded in producing disturbances in sex-hormone levels and reproductive function.([40]) In the closest approximation to human use in these efforts, female monkeys given 7 joints’ worth of THC every day stopped ovulating, but they restarted after a year on this regimen.([41]) In general, the changes induced vary from lab to lab and species to species, and they decline or disappear, even with continued dosing, as the internal system adjusts to the supply of external cannabinoids.

Enormous doses of THC have disrupted sexual development in some animals, but not consistently.([42]) Just one 16-year-old pot smoker who suffered delayed puberty was enough to convince some people that marijuana in adolescence inhibits maturation,([43]) but there is no evidence that real-world use has affected sexualization in humans.

By accepting Kolodny’s disproved conclusions, by extrapolating from short-term effects in animals, and by reasoning from the knowledge that internal cannabinoids certainly do help regulate many hormone systems, some researchers conclude that marijuana must interfere with human sex and reproduction somehow. One of them gingerly lamented the lack of proof of real-world damage thus: “The discrepancies that exist in the hormonal response to cannabinoids in men and between humans and animals have yet to be reconciled.”([44])

Throughout the world, many people consider ganja the most reliable aphrodisiac between people who are already attracted to each other, so it may indirectly contribute to the temporary increase of testosterone in the blood that marks sexual desire in both genders. A majority of the people questioned in the first major American survey of cannabis use said the drug made them more responsive lovers, with an enhanced sense of touch and more fulfilling orgasms.([45]) Over 80 percent of 1,000 people interviewed by Masters and Johnson said it enhanced their enjoyment of sex. A survey of 345 American college students revealed that about half said cannabis made them hornier (39 percent of men and 58 percent of women) and increased their pleasure in lovemaking (60 percent of men and 43 percent of women).([46]) In another survey, of 100 people, two-thirds said marijuana enhanced intimacy, staying power, and orgasm.([47]) Unfortunately, as Mitch Earlywine dryly notes, despite the kind herb’s obvious potential for treating lack of desire, “studies of cannabis’s impact on sexual drives have not been a high priority of most research funding agencies.”([48])

High Crimes

            Demagogues of the 1920s and 1930s sold marijuana prohibition with the claim that it made people violent. They played on white fear of the swarthy underclasses with scare stories about Negroes and Mexicans raping and murdering while out of their gourds on reefer. Bureau of Narcotics chief Harry J. Anslinger fed items from his “gore file” to obliging media dominated by the newspapers owned by William Randolph Hearst—tales of brutal assaults by dope fiends, nearly all of which were distortions or complete fabrications.([49])

            Clinical tests by doctors for the LaGuardia Commission exposed the false link between cannabis and violence: “In a limited number of the subjects there were alterations in behavior giving rise to antisocial expression. … However, any tendency toward violence was expressed verbally and not by physical actions.…”([50]) Commission members concluded, “Juvenile delinquency is not associated with the practice of smoking marihuana,” and “Marihuana is not the determining factor in the commission of major crimes.”([51]) They found only two effects of the drug on crime: It made test subjects less inclined to condemn people who broke the law by smoking marijuana, and it made them less inclined to join the police force.([52])

            There is no credible evidence that cannabis contributes in any way to crime or violence. There aren’t even any myths about pot fiends knocking over gas stations to support their habits. In many jails throughout the world, marijuana is overlooked, or even supplied, by guards, so they have fewer attacks and fights to deal with. Users of cannabis say it reduces aggression—and science backs them up.([53]) Experimenters can’t goad stoned animals into attacking each other unless they starve them first.([54]) The percentage of pot smokers among young delinquents and violent adult arrestees is less than among the general population of their peers.([55]) Two research groups have claimed a tiny correlation between marijuana use and teenage violence, but they neglected to find out whether the perpetrators were high when they committed the acts,([56]) and when one of the groups factored out drinking and prior violence, the cannabis connection disappeared.([57]) Sociopaths, people with oppositional-defiant disorder, i.e., those who break laws simply for the sake of breaking them, may be drawn to cannabis because it’s illegal. Some criminals do smoke marijuana, but most of them started breaking other laws before the pot laws.([58])

Year after year, the Department of Health and Human Services National Household Survey on Drug Abuse estimates that some 45 to 50 percent of adults aged 18 to 34 have tried marijuana, and 5 to 10 percent use it at least semiregularly. Prohibitionists point to one report as evidence that these numbers are higher among murderers, but the connection doesn’t hold up. Interviewers studying 268 murderers found that 72 (27 percent) had smoked marijuana within a day of the homicide, and 18 (6.7 percent) said this had contributed to the crime. But 15 of these were intoxicated with other drugs at the same time—primarily alcohol or cocaine, whose links to aggression are well established. That leaves 3 (1.1 percent) who blamed pot alone. After reviewing the evidence, the researchers concluded that cannabis had played no role in any of the killings.([59])

Psychologists study aggression in the lab using a rigged game. The test subject tries to correctly answer questions or press the proper button faster than an opponent. The winner of each round gets to give the loser an electric shock or take away some of the loser’s points, which are paid off in cash after the game. Evaluators judge the level of hostility displayed, sometimes by letting the subject choose the strength of the electric shock supposedly meted out. But only fake shocks are given to the opponent, who is actually a shill, and the apparatus is set up so that the test subject always loses overall. THC or cannabis generally has no effect on the level of aggression in this test, and in high doses actually decreases it.([60]) One group of researchers reported that eight cocaine-using men, seven of whom had been diagnosed sociopaths, showed increased belligerence while playing this game stoned, but only for the first hour in one of several sessions.([61]) Antitolerance pamphlets often mention this result as proof that cannabis causes violence. Another group has provided equally tenuous evidence that aggression increases in regular users who don’t have any herb.([62])

            When attempting to link grass to crime in an op-ed piece, Clinton’s Secretary of Health and Human Services, Donna Shalala, once wrote, “Young marijuana users are more likely than nonusers . . . to be arrested.”([63]) If a pot smoker had said that, it would be called evidence of brain damage.

Memory and Thought While High

Marijuana changes the way people think when they’re stoned. That’s the whole point, after all. Prohibitionists assume that this change in consciousness is harmful, and since they control the funding agencies, most scientists have asked what the drug is bad for rather than what it’s good for. But, after hundreds of experiments, there are only two mental processes that all researchers agree cannabis is bad for while one is high—short-term memory and estimation of the passage of time. These appear to be two aspects of the same phenomenon: The sense of time expands so that more mental events crowd into consciousness, and, in effect, short-term memory is asked to do the work of intermediate-term memory. Tokers have been saying this all along.

A few researchers have studied marijuana simply by asking users what it does. One of the first to do so was Stanford psychologist Charles Tart, who gave 150 pot smokers a questionnaire asking how often they experienced 200 possible effects while high.([64]) In this and other surveys, the most consistently noted cognitive effect is a decline in short-term memory, which often seems humorous because of what cannabis gives in return. Sixty-five percent of Tart’s interviewees said that, when they were very high, the seconds were so long, there was so much to enjoy in each one, and the rushes of thought and association went by so fast that they sometimes forgot the beginning of a sentence by the time…what was I saying?

Lab work likewise suggests that short-term memory evaporates faster because there’s more stuff flying in through some newly opened window. When stoned people are asked to memorize a list of words, and then to pick out words from this list that are included in a second list presented a short while later, they can do so. They also do well at simply recalling as many words from the original list as possible. In both cases, however, they also falsely remember words that were not on the list. The same applies to recall of sounds, pictures, and stories.([65]) Such misleading “memory intrusions” only seem to occur in meaningless tasks, however. Eyewitness recall of events is not affected.([66]) But Charles Tart also found that cannabis promotes intrusion of true memories that are meaningful to a person—spontaneous and vivid recall of events from one’s past, sometimes with the effect of defanging an unpleasant experience or reliving a pleasant one.

Many users say the flood of ideas makes them less able or willing to concentrate on one activity or follow a single train of thought without getting sidetracked.([67]) This is especially true of nonsense tasks. For example, when watching a series of lights flash on and off in a repetitive sequence for an hour or more, marijuana decreases the mindless alertness (vigilance) required to notice when one light in the sequence is occasionally skipped.([68]) The expanded sense of time makes such a tedious job seem longer, and the increased mental activity makes it more onerous. However, several studies have documented claims that cannabis increases tolerance for dull physically demanding work, such as sugarcane cutting.([69]) That’s why South African diamond- and gold-mine owners used to ignore dagga smoking among their workers.

Probably as a by-product of its effect on short-term memory, the marijuana high impairs people’s mathematical ability. They have particular difficulty adding or subtracting long columns of numbers, even when they’re being paid for each correct answer.([70])

Though not concerned with cannabis, recent research suggests why some people say the drug actually helps them concentrate on certain activities, especially creative efforts that might otherwise seem daunting. People with a lot of short-term memory capacity often carry a bunch of worries in it. They tend to choke in tense situations where performance is expected, like taking a test. People with less short-term memory capacity rely more on other faculties and seem less bothered by pressure.([71]) Perhaps by reducing both anxiety and short-term memory, marijuana helps the high-capacity people focus on the task at hand.

Marijuana does not affect memory in other ways. It does not change the ability to recall lists of words memorized while sober, or one’s vocabulary of words beginning with a specified letter, or obscure television shows.([72]) All studies agree that it does not interfere with recall of things learned before getting stoned.([73]) Moderate doses don’t even interfere with simple short-term memory tasks, such as memorizing pairs of words and recalling one of the pair in response to the other a short time later.([74])

Cannabis does not change any other aspect of mental function in a dramatic or consistent way. Reports of changes in problem-solving ability, sensory perception, information processing, or coordination are invariably minor and contradicted by other reports. The differences are probably due to variations among people in their innate abilities and in their reactions to the drug.([75])

For example, in some experiments, cannabis has slowed reaction time a little; in others, it has not. No one knows the reason for the inconsistent results, but the effect may skew other tests that rely on speed of button-pushing to assess changes in mental function.([76]) The drug does slow reaction time and increase the number of mistakes in more complex meaningless tasks, like pushing specific buttons for specific colored lights, but the amount of the slowdown decreases when people are given a chance to practice the test while high.([77])

            There is an interesting possible effect of cannabis on visual perception that deserves further study. People often say they experience color more richly after smoking grass, but laboratory studies find that they’re less able to distinguish between shades of color, especially blue.([78]) Likewise, many people say they see three-dimensional depth better when stoned, whether in natural landscapes, photographs, or post-Renaissance paintings. But the only lab work to address the issue found that pot seemed to diminish recognition of three-dimensional aspects of pictures in a stereoscope.([79]) Perhaps somewhere in the brain there is a trade-off between accuracy of perception and enjoyment of perception.

One psychological test, the Stroop task, allegedly shows a tendency toward destructive behavior while high. In this test, subjects look at a color name printed in mismatched colored ink, such the word yellow printed in red. They are asked to respond with what is considered to be the unnatural response, the name of the ink color, in this case “red.” Supposedly, this measures people’s ability to inhibit, that is, to “just say no” to natural, impulsive actions like responding in kind to an insult, breaking a diet or a budget, seizing a sexual opportunity([80])—or trying a tempting drug. Not only is this a dubious extrapolation from a simple cognitive phenomenon to much more complex emotional ones. It also assumes that everyone relates to exterior stimuli primarily through words rather than in a more fundamental way through the senses. Marijuana has had inconsistent effects on Stroop-task performance, perhaps due to the button-pushing problem, perhaps by fostering more direct sensory perception—or perhaps by heightening a sense of the absurd.([81])

The laboratory does not lend itself to studies of creative thinking, although a few scientists have noted its oft-reported enhancement by cannabis.([82]) Literary accounts,([83]) on the other hand, abound with descriptions of three effects seldom mentioned in scientific papers: artistic inspiration, spiritual feelings, and laughter. The salient features of modern research on cannabis are its relentless negative bias and its grim humorlessness, though some of it is unintentionally funny. For example, marijuana reduces the ability to correctly read Aristotle’s most opaque prose aloud while hearing one’s own voice echoed in a time-delay tape loop.([84]) Cannabis would be much less appealing if it did not impair performance on this test.

Such experiments indicate a failure to understand, even a refusal to understand, what the drug does or why people use it. Scientists have found that they can almost always produce “impairments” by giving the herb to nonusers, by giving them abnormally high doses, especially of pure THC, and by making them do difficult, monotonous, meaningless, unpleasant things while high, especially without giving them a chance to practice them while high.([85]) With no exceptions that I have discovered, cognitive testing has been done after subjects smoke at least one joint’s worth to get substantially ripped. No one seems interested in the effect of one or two tokes. For most long-term studies, only the heaviest smokers are recruited. Virtually all government-sponsored research takes these approaches. Then, when the 30-second news spot says “marijuana causes” this or that, the qualifiers get left out.

Of course, this is a good way to get grant money. These kinds of studies are also often excused as a reflection of an inferiority complex among social scientists, their yearning for the kind of quantifiable data found in the “hard” sciences like chemistry. They’re more convincingly explained as part of an unacknowledged attempt to create the perfect worker, the soft machine. Sorting bags of dominoes may mimic certain jobs, but it elucidates cannabis only in reverse. It’s like making an ox and a racehorse each pull a cart full of rocks and then saying, “Aha! I told you so. The ox is faster.”