It is time for politicians to put to rest the myth that cannabis is a gateway to the use of other controlled substances — a theory that is neither supported by modern science or empirical data. 

Twenty-nine states, the District of Columbia, Guam, and Puerto Rico now allow medical cannabis, with eight states plus D.C. permitting legal use of recreational weed and Canada on track to do so next year. More publicly traded marijuana stocks are now available, which presents opportunities for investors.

However, there are challenges alongside those opportunities. Here's what you need to know about marijuana stocks before investing.

Some marijuana stocks have greater risk than others

Investing successfully hinges on managing risk effectively. Be aware that some marijuana stocks have significantly greater risk than others.

Decades ago, Canada signed three international treaties, still in force,  in which we agreed to ban marijuana. The federal Liberals have said that they want to legalize recreational pot by July 1, 2018.

Clearly one of those things has to go — and given how thoroughly committed the government is to legalization, it’s pretty clear which one it’s going to have to be.

Health Canada’s crackdown on banned pesticides in the medical marijuana industry is drawing praise from within the sector as the government introduces mandatory safety testing on all products to protect consumers.

Aphria Inc., which has called on the government to introduce stricter safety standards in recent months, said on Thursday that Health Canada’s decision was a welcome move. The company’s chief executive officer, Vic Neufeld, called it “a positive step forward” for the industry.

Health Canada announced last week it will subject companies to mandatory safety testing to ensure their products do not contain dangerous pesticides that can be harmful if inhaled or ingested.

It's an issue that divides society - to smoke or not to smoke.

Throughout the world, a number of countries are slowing changing their laws around medicinal and recreational cannabis use. New Zealand's laws have stayed relatively the same for some time, with the exception of cannabis based products now being approved for use, but still tightly controlled.

So, which countries are leading the way in this area, and where can you use it either for fun, or for well-being?

Here in New Zealand, cannabis remains illegal to possess, and illegal to grow.

Medicinal use is tightly controlled but can be granted by the Ministry of Health.

Across the ditch it's a similar story.

With a little more than a year to go before the federal deadline to legalize marijuana, the incoming provincial government will have to work quickly to implement new provincial pot laws. 

None of the three party leaders has a definite plan on how they want to regulate the drug, but say they will be working on the issue in time for July 1, 2018.

Legalization was a key campaign promise by the Trudeau Liberals in 2015, but Ottawa has given discretion to the provinces over issues such the price of the drug, and how it is distributed and sold. The federal minimum age to buy marijuana will be 18 but provinces are permitted to set an older age limit. 

McNeil: 'Uniform approach' needed

he recreational marijuana industry is expected to take a sip of less than one per cent initially out of annual Canadian alcohol sales once it becomes legal, a new analysis says.

The Anderson Economic Group, a business consulting firm in New York, says legalization of marijuana would sap $160 million out of the country’s $22.1 billion booze sector, rising as use of the drug expands.

While there are numerous unknowns governing the sale of marijuana, the Anderson Economic Group based its projections on alcohol sales in U.S. states that have legalized the drug. It also took into account a host of factors in Canada including spending patterns, income and demographics.

Windsor's Mothers Against Drunk Driving representative wants police in the area to have permission to test the saliva of drivers to determine whether or not they are under the influence of marijuana.

Officers currently rely on the actions of drivers to determine whether they have been using the drug.

Chaouki Hamka, community leader for MADD Windsor Essex County, said police should be allowed to use saliva swabs during roadside tests to determine if someone is driving while stoned.

"Having random breath testing gives the police an alternative tool to crack down on impaired driving, especially when you're under the influence of marijuana," said Hamka. "Too many people are going undetected."

Some major players in the Canadian cannabis industry are bankrolling smaller Canadian marijuana companies, using so-called "streaming" deals to finance their growth plans.

The deals could allow those backers to take leading roles in distributing wholesale and retail marijuana under the forthcoming legal regime.

Streaming is a business model traditionally associated with the mining industry. A backer provides upfront money for infrastructure and capital expenditures in exchange for the right to some of the miner's future production. 

​Cannabis Wheaton, which identifies itself as "the world's first marijuana streaming company," chose its name in reference to well-known silver streaming firm Silver Wheaton, said chairman and CEO Chuck Rifici.

The federal government is hoping to find strength in numbers as it tries to stamp out the illicit marijuana market.

Government officials are collecting data — everything from the street price of pot to how often people light up — to arm themselves in the fight against organized crime's presence in the trade, internal Public Safety Canada documents reveal.

The Liberal government has tabled legislation to legalize and regulate recreational marijuana use, with the aim of keeping pot out of the hands of children while denying criminals the hefty profits.