 Cannabis has been used for thousands of years for both medicinal and recreational purposes. However, in the 20th century, international regulation saw marijuana bands across the globe, from the UK to Jamaica to the USA. Over the last decade, attitudes towards POT have changed. Uruguay and Canada have legalised cannabis for both medicinal and recreational use. In the USA, marijuana is now legal in some form in over 30 states, making it the largest legal market in the world. And in Europe, Germany has one of the fastest growing medicinal cannabis industries predicted to grow from $9 million to $1.6 billion by 2022. From companies growing the herb to distributors to those making cannabis-based products, the global marijuana market is estimated to be worth around $20 billion, a figure estimated to double by 2021. Wider legalisation of the drug has been reflected in the markets with both the NASDAQ and NYSE accepting the listing of cannabis stocks for the first time in 2018. So what does this budding economy mean for traders? And as more countries look set to legalise the drug, are cannabis stocks set for new highs? Opto has identified eight companies to watch in the sector. They include Canada's Canopy Growth, the only cannabis producer to have a joint listing on the NYSE and Toronto Stock Exchange with the ticker Weed. After acquisitions in the Latin market, it's now eyeing opportunities in Europe. Tilray was the first cannabis company to IPO the NASDAQ in 2018. Its share price rocketed from $17 to $300 in just two months but has since come off those highs. And Hexocorp, which distributes easy-to-use cannabis products, looks set to capture a large section of the Canadian market with plans to expand into Latin America and Europe this year. In the short term, as more countries move towards legalising the herb, stocks such as these have the potential to rally, offering traders opportunities. Much like cryptocurrencies, new industries can offer fresh opportunities and risks. The crypto market hit an all-time high of $830 billion in January 2018, but tumbled nearly 80% by the end of the year. And much like the crypto industry, the cannabis industry could be burnt by increased regulation and legal impediments, specifically in the USA. So while forecasts suggest that the marijuana market could hit $146 billion by 2025, traders need to keep a clear head. As global legalisation spreads and talks of regulation increases, stocks could swing sharply in the near future. In the long term, as cannabis settles into the wider drug market, it remains to be seen which companies can stay in the green.