'there is no basis for the belief that Nizari assassins did their business while hopped up on drugs. [...] Legend has it that the Nizaris functioned primarily as assassins. [...] Their leader, known simply as the Old Man of the Mountain, recruited followers by administering an "intoxicating potion" to them and transporting them to a "garden of paradise" to enjoy the forbidden delights of women, drugs and food. The primary ingredient of the potion, according to medieval reports, was hashish. [...] Research by historians such as Bernard Lewis, however, has cast doubt on this lurid picture. [...] The bizarre stories that became so closely connected with the group sprouted from the medieval Muslim majority's attempt to condemn the Nizaris as immoral and heretical'. - http://www.straightdope.com/columns/read/2023/does-assassin-derive-from-hashish
Psychiatric Drugs And Mass Murder: Exploring The Connection
No mention of marijuana in that article.