Dr Lester Grinspoon is Associate Professor Emeritus of Psychiatry at Harvard Medical School. Now one of the most respected and outspoken proponents of cannabis, Dr Grinspoon originally set out to prove it was a harmful drug. In 1967 he began research to scientifically define the dangers of marijuana. His studies led him to a surprising conclusion, the opposite of his hypothesis. Cannabis was not the dangerous drug that he, and the general public, had been led to believe it was.