I worked 7 years in a rehab. The only drug harder to get an addict off of is black tar heroin. After 6 months there I began to realize why back in the 1890s Cocain was considered a harmless stimulant by Dr's and Pharmacists and soft drink manufacturers but weed was considered a dangerous narcotic.
If you could get a guy off pot it took 5 or 6 months. Most coke heads could drop blow in 2 weeks.