Det du egentlig snakker om her er jo gateway teorien.

Her er hvertfall en artikkel som omhandler gateway teorien.

"Alternatively, experience with and subsequent access to cannabis use may provide individuals with access to other drugs as they come into contact with drug dealers. This argument provided a strong impetus for the Netherlands to effectively decriminalize cannabis use in an attempt to separate cannabis from the hard drug market. This strategy may have been partially successful as rates of cocaine use among those who have used cannabis are lower in the Netherlands than in the United States."

Et kjappt søk på google, og det er mange artikler som omhandler dette.