Opinion: These are the new rules for investors who want to buy marijuana stocks

The cannabis sector has had a big drawdown. The crash has several lessons for investors.

If technology stocks are causing you pain, just be thankful you don’t own cannabis shares.

Exchange traded funds including ETFMG Alternative Harvest MJ, 2.01%, AdvisorShares Pure Cannabis YOLO, +1.46% and the simply named Cannabis THCX, +3.05% are at all-time lows.