From Wikipedia: In 1958, while he was an airman first class, his commanding officer recommended him for an early honorable discharge. “In summary, this airman, although talented, will not be guided by policy,” chief of information services Colonel William S. Evans wrote to the Eglin personnel office. “Sometimes his rebel and superior attitude seems to rub off on other airmen staff members.”
Drug use on its own usually doesn’t result in a court martial, which means it normally isn’t a DD.
Drug use would be a less severe separation like an OTH or general discharge.