During the past century, the American attitude toward drugs has swung from one extreme to another. So has Americans' use of drugs. Between World War I and World War II, for example, drug use declined and reached a low point in the 1940s. Cocaine was used in generous amounts at the turn of the century, but use faded by the 1930s. Through experience, uncritical enthusiasm for a drug gradually shifts to rejection.

The problem with recalling these shifts in attitude is that they sometimes span a lifetime or more. A person growing up in America in the 1890s and the 1970s would have the image of a drug-using, drug-tolerating society; a person growing up in the 1940s -- and perhaps in the 2000s -- would have the image of a nation that firmly rejects narcotics. These alternating trends have been characteristic of American attitudes toward mood-altering substances. Whether we can establish a steady, realistic relationship to them is a difficult question.

These gradual shifts in attitude are not forgotten just because they are so slow and lengthy. They are also actively rejected by a strain of perfectionism in American culture -- some might call it moralism -- that yearns for a decisive and universal truth about mood-altering substances. Curiously, the universal truth has fluctuated from seeing mood-altering substances as valuable instruments by which people can attain their full potential and seeing them as poisons that reduce potential. Therefore, we are repeatedly rejecting the foolishness of an earlier generation.

Cocaine harmless? Ridiculous, we replied in 1910. Cocaine harmful? Ridiculous, we replied in 1970. Cocaine harmless? Ridiculous, we reply in 1990.

The reason for this emotional condemnation of earlier attitudes toward drug use is that having the right attitude toward mood-altering substances is important to large numbers of Americans. For instance, one of the major international anti-drug actions, the Hague Opium Convention (1912), came at a time of moral certainty in the United States about the danger of recreational drug use. U.S. diplomats knew that other nations held contrary views, that some obtained revenue from the sale of opium, that others had lucrative commerce in pharmaceuticals like heroin and that some just didn't care. Americans knew what those nations believed and what those nations ought to believe.

Thus many countries were confounded when America went to the other extreme in the 1970s. Near a peak in its drug tolerance, the United States raised before the United Nations the possibility of "decriminalizing" marijuana, consequently confusing a number of delegates. What had happened, the Soviet delegate asked, to the traditional American approach to international drug control? What that delegate and others did not know was that the United States was returning to an attitude similar to one it held in the 1880s, when mood-altering substances were largely unrestricted and widespread.

Now we are once again into an era of intolerance. Opposition to drugs has been growing since 1980, and if history is a guide, it will continue for a long time.

Americans have a tendency to make drug use a symbol. In the 1960s, when drug use for many meant membership in the counterculture, it was a positive one. In the decade before World War I when the use of various drugs was attributed to minority groups against which many held prejudices, it was a negative one. For Americans, use of a mood-altering substance is often more than the physics and physiology of consumption -- it is a gesture of solidarity or defiance.

The United States' experience with this symbolization has been mixed. When certain drugs have been linked to feared ethnic or cultural groups -- even if the linkage is false or unfair -- it has probably contributed to a decline in demand. But we have to be concerned that our current anti-drug movement does not drift into simple associations between, say, inner city blacks and Hispanics and the cocaine problem. Although such an association may actually tend to reduce middle-class white Americans' cocaine consumption, the long-range effect on national unity, aid for the cities and genuine assistance to those who are trying to reclaim their neighborhoods would be destructive.

Another aspect of symbolization is the difficulty in accepting any ambivalence about the wisdom or folly of drug use. Policies of nations such as the Netherlands, which imply that drug use should be officially facilitated to reduce harmful consequences, are out of harmony with our growing intolerance toward dangerous substances. In the American political arena, government actions are part of a moral struggle, and the ultimate statement of condemnation is legal prohibition. As we become more intolerant, we rely more upon law enforcement, and treatment and even research are seen as expensive and inefficient.

We should be taking a lesson from our own history, which indicates that the current drug problem is slowly declining and that extreme agitation with its scapegoating and Draconian penalties can be more damaging than the drugs themselves. The battle against drugs is far from hopeless. But we need to be persistent and determined, not reckless and desperate.

The writer is a professor of psychiatry and history of medicine at Yale. The above is from an address he gave at the Woodrow Wilson International Center for Scholars.