A Harvard Medical School professor who terms himself "conservative about the usage of drugs" yesterday called marijuana "less dangerous than aspirin" in some ways and urged its legalization.

Dr. Lester S. Grinspoon, associate professor of Psychiatry, said that originally his biases "were a little on the 'it's a dangerous drug' side." After three-and-a-half years of research, however, he concluded that what is harmful about marijuana "are the present laws regarding it."

"It is very harmful even to threaten a large segment of our population with incarnation-to criminalize them for smoking marijuana," Grinspoon said.

"There has never been a well-documented case of death being caused by cannabis," he added. "And between 400 and 1000 people die each year from aspirin."

Just Like Prohibition

Grinspoon predicted that within five years "marijuana will either be legalized and regulated, or the laws will be ignored as much as the prohibition was."

"I would treat marijuana much as liquor is now treated," Grinspoon said. "I would have it government-controlled to eliminate 'lacing' it with dangerous drugs, and to give users a good idea of how much they would need to take to get the high they wanted."

He said that he did not support the legalization of hashish, mescaline, LSD, or other, more powerful drugs.

Grinspoon began researching marijuana when he was asked to testify at

a local trial several years ago on the hazards of marijuana usage.

As his work progressed, he became more and more "amazed" at the "bias, the enmity, and the mythology" that colored people's opinions of the drug. "People actually believed that it would degenerate and deteriorate your mind," Grinspoon said.

The outcome of the research was an article appearing in Scientific American last December in which the author concluded that marijuana was less harmful than alcohol or tobacco. He recently finished work on a book called Marijuana Reconsidered, which will be published by the Harvard University Press.