Earlier this month, some online brokerages in Canada received numerous complaints from customers about delays in placing trades and temporary outages. An unexpected spike in trading volume was blamed in large part on trading in the shares of publicly listed cannabis-related stocks.

On one occasion, two days before Jan. 1, 2018, the Investment Industry Regulatory Organization of Canada halted trading in four of these stocks for about 10 minutes because of significant price swings in the shares.

The heavy volume and sudden swings in share price in these stocks has not been an isolated event in recent months.