(CNN) An act to legalize the use of marijuana for medicinal purposes was passed by German parliamentarians. They voted unanimously in favor of the new bill, first approved by the country's cabinet in May 2016.

On January 19, votes were unanimous in favor of the new "cannabis as medicine" law, which will come into effect March 2017.

People with multiple sclerosis and other severe illnesses will be able to obtain the drug legally with a prescription. Doctors will also be able to prescribe marijuana or cannabis to patients for whom the drug could alleviate symptoms, such as chronic pain or nausea, or who may see a positive effect on their disease progression, according to a statement (PDF) from Germany's Federal Ministry of Health.

"Critically ill people must be cared for in the best possible way," Federal Health Minister Hermann Gröhe said in a statement, adding that "costs of using cannabis for medicinal purposes will be met by the health insurance companies of the critically ill, if no other form of treatment is effective."

The law was welcomed by parties on both the left and right.

Germany will now create a state-regulated program to cultivate the crop for its medicinal use in the future and to ensure its quality. Until then, plants will be imported.

Personal possession of the drug remains illegal in Germany, though small quantities in possession are not usually prosecuted.

Germany now joins a list of countries experimenting with new laws, both medicinal and recreational, regarding marijuana control.

The global picture

Marijuana, or cannabis, is "the most widely cultivated, produced, trafficked and consumed drug worldwide," according to the World Drug Report , but its legality has long been a topic of debate worldwide.

In the US, Maine recently confirmed legalized recreational marijuana use, joining seven other states and the District of Columbia. Medical marijuana is now legal in more than half of US states.

This mirrors a global trend. In 2016, Canadian officials said they aim to introduce legislation in 2017 to legalize and regulate marijuana. Uruguay is the only other country to legalize cannabis. Ireland, Australia, Jamaica and Germany approved measures in 2016 for its medicinal use, while Australia also granted permission for businesses to apply for licenses to manufacture or cultivate marijuana products for medicinal purposes and to conduct related research. Decisions are still pending in South Africa.

They join more than 20 countries exploring the possible benefits of legalization. But as with the drug itself, the laws vary, as does the potency of control, and the world is waiting to learn what will work best.

"We need a lot more data to inform the policies that are happening," said Ryan Vandrey, associate professor of behavioral pharmacology at Johns Hopkins University in the United States. He has no stance on whether marijuana is "good or bad," he said, but wishes policies around the drug had the data typically required when approving a new therapy.

"There are a number of things that can happen when these policies change," he said, adding that social and cultural norms will ultimately define the real-life effect of these changes. "You can have vastly different impacts from the same change in policy," he said.

Hard to knock medicinal benefits

Portugal is a pioneer when it comes to drug reform laws, as the nation decriminalized the possession of all drugs -- not just cannabis -- for personal use in 2001. As a result, the country holds the greatest body of evidence about the impact such a change can have on policy.

"We were a social laboratory," said João Castel-Branco Goulão, director-general of the General-Directorate for Intervention on Addictive Behaviours and Dependencies in Lisbon. But filtering out the specific impact in terms of cannabis is difficult.

"Experiments are now taking place in other parts of the world," he said.

Having trialed drug reform for more than a decade, Goulão believes that when it comes to defining what's needed for cannabis, there must be a clear distinction between discussions for medicinal and recreational use to "avoid confusion."

"People mix medicinal and recreational use," he said. However, he acknowledges that the basis for medicinal benefits from marijuana is strong, with a range of experts, including himself, recognizing its use to alleviate chronic pain, muscle spasms, anxiety, and nausea and vomiting -- most of which are linked to a variety of disorders, including multiple sclerosis and cancer treatment, which underlies Germany's rationale behind it's new ruling.

"I have no problems with medicinal marijuana," Goulão said. "There are conditions I believe can benefit from cannabis use."

The benefits are attributed to two main components of cannabis: the psychoactive component THC or the plant's extract, CBD oil. The latter is linked to improving anxiety as well as epileptic seizures, proving to be life-saving for children with a severe form of epilepsy.

"CBD can stop the fits. It's quite remarkable," said Dr. Mike Barnes, professor of neurological rehabilitation at the University of Newcastle in the UK.

Barnes recently wrote a report highlighting the medicinal value of marijuana for the All Party Parliamentary Group for Drug Policy Reform in the UK. The drug is categorized as schedule I, defined as having no medicinal value.

"Clearly, that is wrong," said Barnes, whose research investigates the benefits to patients with brain injuries and multiple sclerosis. "It ought to be legalized for medicinal use," he said -- a thought most experts echo, as long as it's adequately informed and regulated.

"If they're going to do it, do it right," said Vandrey, who wants laws to ensure that the best evidence is analyzed and that manufacture, potency and labeling are also regulated, as with any drug.

"It's not medicine if you're just buying it from a street dealer," he said. "We don't have any other medicines where concentration differs every time we buy it. ... It needs to be treated as a medicine."

Vandrey cites Canada and Uruguay as countries setting this example. Their new laws provide government-controlled sources of marijuana for anyone, not just those who need it for medical use.

These two countries "are the only ones that have nationally approved cannabis," he said. "They provide a government-sourced product."

The jury is out on recreational use

All three experts believe the argument to legalize marijuana for recreational use isn't as straightforward as the case for medicinal use.

They believe the intermittent step of medicinal legalization provides insight into how the drug will penetrate the population when access is made easier.

"This gets into the realm of social law," said Barnes, who thinks marijuana should be made available medicinally first. "I would support allowing people to grow it in their backyard, like in the US, but then you don't get the control."

Multiple countries have decriminalized personal possession of marijuana, including the Netherlands, Mexico, Czech Republic, Costa Rica and Portugal, in an attempt to address societal problems associated with its use, according to Barnes.

The research emerging is still young and eagerly awaited, but Goulão has already seen changes among the Portuguese population: namely, a drop in stigma associated with drug use.

"This is the most positive outcome," he said, highlighting that having an open dialogue about drugs, including marijuana, in family, school and workplace settings means people more readily seek help if they become addicted.

Evidence also shows that removing penalties for drug use hasn't led to an increase in drug use in Portugal, as many voices in the opposition would argue. Instead, it reinforces the fact that criminal drug laws do little to deter people from using them, according to a report by the United Nations Office on Drugs and Crime.

Despite these benefits, Goulão believes that leaping straight into full legalization, rather than decriminalization, is not a wise move.

"They are jumping a step," he said, referring to countries such as Uruguay, Canada and some US states. They should instead "decriminalize and watch carefully," he said. "I think we still don't have evidence that (legalization) is positive."

'Too young'

Vandrey believes that the field as a whole is "too young to see evidence of the benefits," adding that the world now needs to wait and learn from the wide range of experiments currently underway in different countries.

But he agrees with Goulão that leaping forward may not be the right decision.

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"People need to recognize the risks and benefits of cannabis for any purpose," he said, highlighting that although the majority of people may not experience side effects, others will find it harmful, such as those with any family history of psychosis or schizophrenia, or adolescents whose brain development may be impaired if they consume the drug too early in life.

"There's huge variability to how people will respond to it," Vandrey said. But information coming in might make clear the best way to regulate the drug in coming years.

"It's going to take five to 10 years to really understand the impact these changes in law will have," he said, again stressing the key role cultures will play in defining this. The impact in Germany, for example, may differ from states in the US.

Goulão added, "It's not going to be easy to change the paradigm in some countries."

But one thing is clear: The wheels are in motion, and the marijuana movement is firmly underway.

"It's going to be very interesting to see what happens," Vandrey said.