Our fight against illegal drugs is severely weakened by the common claim that marijuana (also called pot) is relatively harmless. Research on marijuana in the 1970s, supported by the U.S. National Institute on Drug Abuse (NIDA), proved that pot is highly dangerous.

Friends of Andy Williams, the 15-year-old who killed two students and wounded 13 in a California high school last month, reported that he smoked marijuana regularly before going to class in the mornings, including the morning of the shootings.

In 1970, typical marijuana contained 1 percent THC, the intoxicating chemical in pot, and the best had 3 percent. New varieties of marijuana have been developed that are much more potent and dangerous; typical street pot today has 12 percent THC and some has 25 percent.

Not all pot smoking leads to heroin or cocaine, but practically no one uses cocaine or heroin who has not smoked pot extensively. The reason is apparent when we understand the very slow action of THC in the body.

THC is strongly fat soluble, which means that THC dissolves readily in fat but cannot dissolve in water or in blood. It is well known that fat-soluble drugs operate slowly.

THC is highly potent, but appears to be mild because very little reaches the brain at the time of the "high." Most of the THC entering the body is stored in fat, which releases it slowly over many weeks.

When a person smokes pot regularly, a large supply of THC builds up in the body's fat, and its slow release into the blood produces continual sedation. Since THC is continually in the body, the "high" from pot gradually diminishes and pot smokers often take other drugs to get a kick.

Nevertheless, they continue to smoke pot as they use other drugs because pot appears to make them "feel good all the time." Most pot smokers also drink alcohol heavily and, because THC inhibits nausea, a pot smoker can consume a lethal dose of alcohol without getting sick and vomiting.

Teens often play around with pot, thinking it is harmless fun and no different from alcohol. They don't realize that THC is building up in their bodies and keeping them sedated all the time.

With their minds confused by marijuana, it is difficult to escape from the trap. It takes over a month of abstinence before a regular pot smoker can think clearly again, and THC can be detected more than two months after a person quits pot.

Because marijuana operates so slowly, its harm is obscured and the damage is often attributed to other drugs used by the pot smokers. Nevertheless, medical evidence has proven that marijuana itself severely damages the brain, the chromosomes, the hormones, the lungs, the immune system, and the sex and reproductive organs. Teenagers are particularly vulnerable because pot smoking can delay and even halt the process of sexual development.

Some people support the legalization of marijuana in the naive belief that this will take profits out of illegal drug sales and thereby reduce crime. But pot is cheap to grow and is not the source of the big drug profits.

The drug lords would be glad to give away marijuana free if they could. That would vastly increase the number of cocaine and heroin addicts who use those highly profitable drugs.

It is obvious that plenty of money is flowing from somewhere for the legalization of marijuana in general, as well as specifically for medical use. Expensive campaigns have successfully passed referenda in eight states and carried this issue to the Supreme Court, which heard oral arguments last week.

The legalization of marijuana for medicine is an indirect means of legalizing pot for recreational use and legitimizing it in the public's mind. THC is already available in pill form with a physician's prescription, and there is no legitimate need for raw marijuana as medicine.

THC as medicine can be dangerous. While THC reduces the nausea from chemotherapy, THC severely weakens the body's immune system and makes the patients more susceptible to infectious diseases.

An excellent reference to marijuana research is Nahas and Paton, eds., "Marijuana, Biological Effects" (Pergamon Press, 1979), the proceedings from the 1978 Congress of the International Union of Pharmacological Sciences. An article by Dr. Robert Heath showed that marijuana severely damaged the brain waves and brain cells of monkeys.

The 1988 White House Conference for a Drug-Free America strongly recommended an independent evaluation of the National Institute on Drug Abuse, which cancelled research about marijuana in 1980 and since then has not supported any marijuana study of significance.

We urgently need that long overdue evaluation plus more research on the harmful effects of marijuana, the drug that creates the market for the other illegal drugs.