Updated: Apr 14
How Lester Grinspoon became the intellectual leader of the cannabis movement.
As America’s socially turbulent 1960s drew to a close and newly-elected president Richard Nixon was codifying his anti-drug agenda into law, a handful of pro-pot activists arose to challenge those efforts. These reformers found an unlikely and invaluable ally in a conservative, middle-aged associate professor from Harvard by the name of Lester Grinspoon, MD.
Born and raised in nearby Newton, Massachusetts, Grinspoon worked his way into Harvard Medical School, where he received his doctorate in Psychiatry in 1955 and later accepted a teaching position. His academic career remained rather unremarkable until a decade later when he met young astronomer Carl Sagan (later of Cosmos fame) at a faculty dinner. The two intellectual giants immediately bonded over their mutual opposition to the Vietnam War, and a lifelong friendship was sparked.
But before long, Grinspoon realized that Sagan and others in their intellectual circle enjoyed smoking marijuana and even suggested that he try it. Both intrigued by his friend’s affinity for the drug and concerned by what he believed was a dangerous habit, Grinspoon did what any scientist worth their salt might do—he started researching it.
When he began his study of marijuana in 1967, Grinspoon’s initial intention was to "define scientifically the nature and degree of those dangers" and persuade Sagan to stop using it. Instead, the evidence led him to the opposite conclusion—that "there was little empirical evidence to support my beliefs about the dangers of marijuana," that it was “remarkably non-toxic,” and that it may actually have some beneficial medicinal applications. Grinspoon published his initial findings in the December 1969 edition of Scientific American, in an article called simply “Marihuana.” 
“Based on the reaction to that [article], he was encouraged to do a book-length exposition of what he had learned,” Grinspoon’s son David recalls, “which was basically that he had been brainwashed along with everybody else into thinking that marijuana was this dangerous substance.”
Two years later, he published the book Marihuana Reconsidered (Harvard University Press), in which he dispels many of the myths surrounding the much-maligned herb.
“I have concluded,” Grinspoon writes, “that marijuana is a relatively safe intoxicant which is not addicting, does not in and of itself lead to the use of harder drugs, is not criminogenic, and does not lead to sexual excess.” He also noted that the only real harm associated with cannabis was, in his opinion, “the way we as a society were dealing with people who use it.”
The book also features a passionate essay extolling the plant’s virtues by an anonymous cannabis user dubbed “Mr. X,” whose identity remained a family secret for over 30 years. Mr. X, it turned out, had been Sagan all along—a fact that Grinspoon only revealed a few years after Sagan’s death in 1996.
Marihuana Reconsidered’s impact was immense and immediate: disdained and disowned by his Harvard peers, but extolled by the fledgling legalization community, for whom it was a valuable resource and a validation of their mission.
“Lester, without question, was the intellectual leader of the entire movement from the moment his book was published in 1971,” asserts NORML founder Keith Stroup. “Lester Grinspoon’s book was the Bible.”