Smoke alarm.

This weed will make you stupid, unemployable, and lethargic. Now it's pot. It used to be tobacco.

It makes you stupid. It turns teenagers into ne'er-do-wells and juvenile delinquents. It ruins academic performance, stifles ambition, and impairs efficiency at work. It leads to the use of other drugs. Today it's marijuana. Eighty years ago, it was tobacco, especially in the form of cigarettes.

"No boy or man can expect to succeed in this world to a high position and continue the use of cigarettes," Philadelphia Athletics Manager Connie Mack wrote in 1913. Biologist David Starr Jordan, the first president of Stanford University, concurred. "The boy who smokes cigarettes need not be anxious about his future," he said. "He has none."

In 1914 the industrialist Henry Ford published The Case Against the Little White Slaver, which included condemnations of cigarettes from entrepreneurs, educators, community leaders, and athletes. Thomas Edison, who contributed to Ford's booklet, was simply repeating a widely accepted notion when he observed that cigarette smoke "has a violent action on the nerve centers, producing degeneration of the cells of the brain, which is quite rapid among boys. Unlike most narcotics this degeneration is permanent and uncontrollable."

The anti-tobacco propaganda of this period, when marijuana was still legal but cigarettes were banned in more than a dozen states, shares some prominent themes with contemporary anti-pot propaganda. Opponents of tobacco depicted cigarettes as a foreign threat to the youth of America, sapping their energy and intelligence. They described the effects of cigarettes in terms that would later be associated with the "amotivational syndrome" supposedly caused by marijuana. They claimed that smoking led to crime, brain damage, lower productivity, and narcotic addiction. In response, they urged children to make pledges of abstinence.

These similarities are especially striking because of the marked pharmacological differences between tobacco and marijuana. The parallels suggest that responses to drug use have less to do with the inherent properties of the substance than with perennial fears that are projected onto the chemical menace of the day.

This is not to say that tobacco and marijuana are harmless. The anti-cigarette movement is far more influential today than it was in 1914, mainly because of scientific evidence that has emerged since then concerning the long-term health consequences of smoking. But today's anti-smoking activists worry about lung cancer, heart disease, and emphysema, not laziness, crime, and brain damage. When they claim that smoking hurts productivity, they are thinking of the habit's effect on physical health, not its impact on ambition or intellect. Despite the continuing controversy over smoking, the concerns about mental decay and moral corruption voiced by opponents of cigarettes early in this century seem quaint and fanciful today.

When it comes to marijuana, however, those charges still ring true with many Americans. There is some basis, after all, for pot-head stereotypes. People who are under the influence of marijuana most of the time, like people who are drunk most of the time, may not get good grades in school or promotions at work. But that does not mean that occasional marijuana use renders people incapable of academic or professional success, any more than an occasional drink does. The staunchest opponents of marijuana invest the drug with the power to permanently transform people, ruining their potential and turning them against society. Before we accept that notion, it's worth reflecting on the fact that people once said much the same thing about cigarettes.

Historical perspective is especially important in light of recent trends. According to government-sponsored surveys, teenage marijuana use has been rising since 1992, following a 13-year decline. In the National Household Survey, the share of 12-to- 17-year-olds reporting past-month use of marijuana rose from 4 percent in 1992 to 6 percent in 1994. In the Monitoring the Future Survey, the share of high school seniors who said they had used marijuana in the previous year rose from 21.9 percent in 1992 to 34.7 percent in 1995. These figures are still well below the peak levels seen in 1979 (16.8 percent and 50.8 percent, respectively), but the increases have aroused concern among parents and educators.

Citing the survey data, drug warriors such as Sen. Orrin Hatch (R-Utah) have criticized the Clinton administration for not doing enough to suppress drug use and have called for greater emphasis on interdiction and enforcement. But the government is already arresting more people for marijuana possession than ever before, suggesting that another crackdown may not be effective. Furthermore, alcohol and tobacco use are also rising among teenagers, something that President Clinton's lack of enthusiasm for the war on drugs can hardly explain. Given the emotional resonance of pot-smoking kids, however, there is a real danger that Clinton or a Republican successor will take Hatch's advice, pushing the pendulum of drug policy back toward the hysteria of the late 1980s. In this context, the parallels between current fears about marijuana and earlier fears about tobacco are instructive. They do not demonstrate that worries about pot are entirely illusory, but they suggest that we should be wary of overreaction.

Although tobacco had been widely used by Americans since colonial times, cigarettes did not catch on until after production was mechanized in the 1880s. Per capita consumption of cigarettes rose nearly a hundredfold between 1870 and 1890, from less than one to more than 35. In 1900 chewing tobacco, cigars, and pipes were still more popular, but by 1910 cigarettes had become the leading tobacco product in the United States. Per capita consumption skyrocketed from 85 that year to nearly 1,000 in 1930.

The rise of the cigarette caused alarm not only among diehard opponents of tobacco but also among pipe and cigar smokers (such as Edison), who perceived the new product as qualitatively different. Critics believed (rightly) that cigarettes were more dangerous to health because the smoke was typically inhaled. They also worried that boys and women would be attracted by the product's milder smoke and low price. "The cigarette is designed for boys and women," The New York Times declared in 1884. "The decadence of Spain began when the Spaniards adopted cigarettes, and if this pernicious practice obtains among adult Americans the ruin of the Republic is close at hand."

At first the anti-cigarette campaign, which had close ties to the temperance movement, focused on restricting children's access. By 1890, 26 states had passed laws forbidding cigarette sales to minors, but many children continued to smoke. Led by Lucy Page Gaston, a former teacher from Illinois whose career as a social reformer began in the Women's Christian Temperance Union, the anti-cigarette crusaders next insisted that complete prohibition was necessary to protect the youth of America. Between 1893 and 1921, 14 states and one territory (Oklahoma) enacted laws banning the sale of cigarettes, and in some cases possession as well. Such laws were supported by the cigar industry, which saw its business slipping away to a new competitor.

Upholding Tennessee's ban in 1898, the state Supreme Court declared that cigarettes "are wholly noxious and deleterious to health. Their use is always harmful; never beneficial. They possess no virtue, but are inherently bad, bad only. They find no true commendation for merit or usefulness in any sphere. On the contrary, they are widely condemned as pernicious altogether. Beyond any question, their every tendency is toward the impairment of physical health and mental vigor."

In contrast to contemporary anti-smoking activists, who talk almost exclusively about the habit's effect on the body, turn-of-the-century critics were just as concerned about its impact on the mind. In the 1904 edition of Our Bodies and How We Live, an elementary school textbook, Dr. Albert F. Blaisdell warned: "The cells of the brain may become poisoned from tobacco. The ideas may lack clearness of outline. The will power may be weakened, and it may be an effort to do the routine duties of life.... The memory may also be impaired."

Blaisdell also reported that "the honors of the great schools, academies, and colleges are very largely taken by the abstainers from tobacco.... The reason for this is plain. The mind of the habitual user of tobacco is apt to lose its capacity for study or successful effort. This is especially true of boys and young men. The growth and development of the brain having been once retarded, the youthful user of tobacco has established a permanent drawback which may hamper him all his life. The keenness of his mental perception may be dulled and his ability to seize and hold an abstract thought may be impaired."

In the 1908 textbook The Human Body and Health, biologist Alvin Davison agreed that tobacco "prevents the brain cells from developing to their full extent and results in a slow and dull mind."' He added, "At Harvard University during fifty years no habitual user of tobacco ever graduated at the head of his class."

The dull, listless underachievers described by Blaisdell, Davison, and other tobacco opponents resemble contemporary portrayals of marijuana users. In 1989 William Bennett, then director of the Office of National Drug Control Policy, explained how smoking pot affects young people: "It means they don't study. It causes what is called 'amotivational syndrome,' where they are just not motivated to get up and go to work."

In recent years the Partnership for a Drug-Free America, which is supported partly by donations from tobacco companies, has helped reinforce this stereotype. One of the Partnership's television spots shows two young men smoking marijuana, one watching TV, the other ridiculing warnings about the dangers of pot: "We've been smoking for 15 years, and nothing has ever happened to me." Then we hear the voice of his mother, asking him if he's looked for a job today. "Marijuana can make nothing happen to you, too," the announcer says.

Another Partnership commercial shows a stoned teenager turning down invitations from friends to play baseball, go skate-boarding, or listen to music. "You always thought marijuana would take you places," the announcer says. "So how come you're going nowhere?" The most notorious anti-pot ad from the Partnership purported to contrast a normal EEG reading with the EEG reading of a marijuana smoker. It was later revealed that the second display actually showed the brain waves of someone asleep or in a coma. Another spot, "No Brainer," compared the effects of smoking marijuana to the effects of being repeatedly hit in the head by a professional boxer.

The tricks of anti-pot propaganda are usually more subtle, however. A common approach is to cite the immediate effects of smoking marijuana without noting that they disappear when the drug wears off. In a joint statement that accompanied the release of a 1995 report called Legalization: Panacea or Pandora's Box (you can guess which side they came down on), Bennett and Joseph Califano, the former Health, Education, and Welfare secretary who heads the Center on Addiction and Substance Abuse, said that "marijuana use...savages short-term memory, sharply curtails ability to concentrate and diminishes motor functions."

A pamphlet from DARE (Drug Abuse Resistance Education) declares, "Young people who smoke marijuana heavily over long periods of time can become dull, slow-moving, and inattentive. These 'burned-out' users are sometimes so unaware of their surroundings that they do not respond when friends speak to them, and they do not realize they have a problem." In the 1985 book Marijuana Alert, Peggy Mann suggested that diminished mental capacity is a persistent trait of pot smokers, intoxicated or not.

Promoters of this idea will be photocopying a study that appeared in the February 21 Journal of the American Medical Association. The researchers found that, after abstaining for at least 19 hours, heavy pot smokers (who used marijuana daily or almost daily) performed slightly worse on tests of learning and attentiveness than occasional pot smokers did. (The two groups scored about the same on basic memory tests.) Since the heavy users were more likely to have smoked marijuana recently, the results may indicate a "hangover" effect.

The lead researcher, Harvard psychiatrist Harrison G. Pope Jr., told Harvard Magazine that, among the light smokers, "total lifetime consumption did not predict results on the cognitive tests.... My bet is that there really is a residual effect caused by drug residue." Another possibility is that people who are inclined to smoke pot heavily are, on average, somewhat less attentive than other people to begin with. A third possibility is that the heavy smokers were used to functioning under the influences of marijuana and were distracted by its absence. Although this study does not demonstrate permanent impairment (or negative effects from occasional use), anti-pot propagandists will probably use it to keep alive the notion that marijuana causes brain damage.

Employers are not eager to hire dim-witted layabouts, whatever they're smoking. "The time is already at hand when smokers will be barred out of positions which demand quick thought and action," wrote Charles B. Towns, operator of a New York drug and alcohol hospital, in 1912. Thomas Edison declared, "I employ no person who smokes cigarettes." With Edison and Henry Ford leading the way, many prominent businessmen adopted the same policy during the first two decades of the century. Hundreds of large companies, including Montgomery Ward and Sears Roebuck, refused to hire smokers.

Similarly, in the 1980s and '90s employers have become increasingly concerned about the impact of marijuana and other illegal drugs on productivity. Many companies now require job applicants to undergo urine tests, a policy encouraged by hyperbolic claims about the costs of drug use. "Last year alone," asserted a series of Partnership for a Drug-Free America ads in 1991, "America's businesses lost more than $60 billion to drugs. So this year, most of the Fortune 500 will be administering drug tests." The $60 billion figure, which was also cited by President George Bush and widely reported in the news media, included an estimate of "reduced productivity due to daily marijuana use." The estimate came from a 1982 study that found adults who had smoked marijuana for at least 20 out of 30 days (at any point in their lives) had lower household incomes, on average, than adults who hadn't. The researchers simply assumed that the difference was due to the influence of marijuana.

In addition to their alleged effects on motivation, intellectual performance, and productivity, both tobacco and marijuana have been tied to crime. "Recent careful investigations by many persons," Davison reported in his 1908 book, The Human Body and Health, "show that cigarette smoking not only clouds the intellect, but tends to make criminals of boys. Dr. Hutchison, of the Kansas State Reformatory, says: 'Using cigarettes is the cause of the downfall of more of the inmates of this institution than all other vicious habits combined.' Of 4117 boys received into the Illinois State Reformatory, 4000 were in the habit of using tobacco, and over 3000 were cigarette smokers." In 1904 Charles B. Hubbell recalled that during his service as president of New York City's Board of Education, "it was found that nearly all of the incorrigible truants were cigaret fiends." He added that "the Police Magistrates of this and other cities have stated again and again that the majority of juvenile delinquents appearing before them are cigaret fiends whose moral nature has been warped or destroyed through the instrumentality of this vice."

While most of the critics who blamed cigarettes for crime implied that the effect was pharmacological, Henry Ford had a somewhat more sophisticated theory. "If you will study the history of almost any criminal you will find that he is an inveterate cigarette smoker," he said. "Boys, through cigarettes, train with bad company. They go with other smokers to the pool rooms and saloons. The cigarette drags them down."

Although drug warriors nowadays rarely claim that marijuana causes crime, that charge played an important role in building support for state and federal prohibition in the 1920s and '30s. A 1938 book, Marijuana, America's New Drug Problem, quoted an account by New Orleans Public Safety Commissioner Frank Gomila of a "crime wave" in the late '20s: "Youngsters known to be 'muggle-heads' fortified themselves with the narcotic and proceeded to shoot down police, bank clerks and casual bystanders. Mr. Eugene Stanley, at that time District Attorney, declared that many of the crimes in New Orleans and the south were thus committed by criminals who relied on the drug to give them false courage and freedom from restraint. Dr. George Roeling, Coroner, reported that of 450 prisoners investigated, 125 were confirmed users of marihuana. Mr. W.B. Graham, State Narcotic Officer, declared in 1936 that 60 percent of the crimes committed in New Orleans were by marihuana users."

Harry J. Anslinger, head of the Federal Bureau of Narcotics from 1932 to 1970, promoted the notion that marijuana causes violence to generate support for a national ban. During the '30s lurid newspaper and magazine stories about marijuana murders - in one case, a Florida youth was said to have hacked his family to death with an ax while under the influence - helped create a climate of alarm.

Tobacco and marijuana have also been charged with subtler effects on behavior. "The action of any narcotic is to break down the sense of moral responsibility," wrote Towns, the drug treatment entrepreneur, in 1912. "If a father finds that his boy is fibbing to him, is difficult to manage, or does not wish to work, he will generally find that the boy is smoking cigarettes.... The action of a narcotic produces a peculiar cunning and resource in concealment." Noting the rudeness of smokers who light up despite the complaints of bystanders, Towns concluded that "callous indifference to the rights of others" was another effect of the drug. In Our Bodies and How We Live, Blaisdell agreed that "the effect of tobacco on the moral nature often shows itself in a selfish disregard for the rights of others."

It seems that pot, too, fosters dishonesty and rudeness. "Among the psychological effects of heavy pot use cited by teachers and parents," The New York Times Magazine reported in 1980, "are a loss of interest in schoolwork, a tendency to lie without feelings of guilt ('She stared me straight in the face,' one mother said of her junior-high-school daughter, 'tears running down her cheeks, swearing she was telling the truth about something, and I knew she was lying') and a change in attitude toward the family. 'I realized,' said a woman of her 12-year-old, 'that right under our noses our happy, lovely little girl had turned into a sullen, alienated, unreasonable creature.'" As these accounts suggest, the symptoms of marijuana use, like the symptoms of tobacco use, are often hard to distinguish from the symptoms of adolescence.

A 1990 booklet produced by the U.S. Department of Education, Growing Up Drug Free: A Parent's Guide to Prevention, offered a list of warning signs: "Does your child seem withdrawn, depressed, tired, and careless about personal grooming? Has your child become hostile and uncooperative? Have your child's relationships with other family members deteriorated? Has your child dropped his old friends? Is your child no longer doing well in school - grades slipping, attendance irregular? Has your child lost interest in hobbies, sports, and other favorite activities? Have your child's eating or sleeping patterns changed? Positive answers to any of these questions can indicate alcohol or other drug use." On the other hand, the booklet conceded, "it is sometimes hard to know the difference between normal teenage behavior and behavior caused by drugs."

Tobacco and marijuana have been condemned not only because of their inherent dangers but because they supposedly lead to the use of other drugs. The psychiatric pioneer Benjamin Rush offered an early version of the "gateway" or "stepping-stone" theory in 1798. Rush, who had already described the inexorable slide into habitual drunkenness among those who developed a taste for liquor, said chewing or smoking tobacco contributed to alcoholism by creating a peculiar kind of thirst: "This thirst cannot be allayed by water, for no sedative or even insipid liquor will be relished after the mouth and throat have been exposed to the stimulus of the smoke, or juice of Tobacco. A desire of course is excited for strong drinks, and these when taken between meals soon lead to intemperance and drunkenness." In 1912 Towns took the notion a step further, saying tobacco leads to alcohol, and alcohol leads to morphine.

The gateway theory is also the last resort of drug warriors who are frustrated by the lack of evidence that marijuana is a menace. In the 1984 book Getting Tough on Gateway Drugs, Robert DuPont estimated that "up to 50 percent of regular users of marijuana also use heroin." In its 1995 paper on drug legalization, Califano's Center on Addiction and Substance Abuse reported that "12 to 17 year olds who smoke marijuana are 85 times more likely to use cocaine than those who do not."

Formulations of this kind obscure two crucial points: First, most marijuana users never even try another illegal drug, let alone use it regularly. Second, it is not safe to conclude from the fact that marijuana users are more likely to use heroin or cocaine that marijuana use results in heroin or cocaine use. (It is probably also true that adults who wear jeans more than three days a week and people who ride motorcycles without a helmet are more likely to try heroin or cocaine.) In this case as in so many others, anti-drug polemicists tend to confuse correlation with causation.

Given the hazards thought to be associated with tobacco and marijuana use, the safest course would seem to be early intervention aimed at preventing youthful experimentation. Accordingly, opponents of both drugs have formulated abstinence pledges, a device borrowed from the temperance movement.

George Trask, a Massachusetts minister who founded the American Anti-Tobacco Society in 1850, visited schools around the country and urged young people to take the Band of Hope pledge: "I hereby solemnly promise to abstain from the use of all Intoxicating Liquors as a beverage; I also promise to abstain from the use of Tobacco in all forms, and all Profane Language." In the 1890s Lucy Page Gaston adopted a similar strategy, leading boys and girls in the Clean Life Pledge: "I hereby pledge myself with the help of God to abstain from all intoxicating liquors as a beverage and from the use of tobacco in any form."

In the 1980s First Lady Nancy Reagan, who adopted drug education as her pet cause, famously urged children to "Just Say No." Kids who joined the clubs sponsored by Just Say No International had to sign this statement: "I pledge to lead a drug-free life. I want to be healthy and happy. I will say no to harmful drugs. I will help my friends say no. I pledge to stand up for what I know is right."

These pledges may seem naive and simplistic, but they reflect a perfectly understandable desire to protect children from danger and make sure they grow up right. Current fears about marijuana and other illegal drugs, like turn-of-the-century fears about cigarettes, express the sort of worries that reappear in every generation. Parents naturally want their children to be smart, to do well in school, to respect authority, and to become productive, responsible adults. The dull, lazy, rebellious, and possibly criminal teenager - the cigarette fiend or pothead - is every parent's nightmare. Adults who have no children of their own worry that other people's kids will become tomorrow's parasites or predators, bringing decline and disorder.

Despite all the alarm that drug scares seem to generate, projecting these fears onto physical objects can be reassuring: Just keep the kids away from tobacco or marijuana (or alcohol or LSD), we are implicitly told, and they will turn out OK. As symbols of all the things that might go wrong on the path from birth to maturity, drugs offer what every adult confronted by a troublesome teenager longs for: the illusion of control.

Senior Editor Jacob Sullum ([e-mail]) is writing a book about the anti-smoking movement for The Free Press.