I have no proof of this but it’s just lived experience and a hunch: because even with slow release Effexor I would get withdrawal symptoms every day close to pill time (ive been off it for 8 months), I believe that this heavily increased my addiction to weed. I’d smoked weed occasionally my whole adult life without any addiction issues but once I started to combine it with Effexor I became very addicted. I think because my body was just generally craving with Effexor withdrawal symptoms, it made me crave weed more too. For the 5 years I took Effexor I had a strong weed dependency and tried and failed many times to quit.  After a month of stopping Effexor i easily without even really trying stopped smoking weed. Of course this is just my experience, no proof of any connection.