The latest United Nations World Drug report shows a dramatic rise in the use of cannabis in the United States over the past decade. The number of daily users grew by two-thirds in the period just before and since the drug's decriminalisation in some US states.
The trend to decriminalise marijuana is gaining momentum, in the United States, Latin America, Australia, Germany and, now, Austria.
At a formal ceremony in the Austrian parliament, a campaign group presents a petition containing 10,000 signatures.
It calls on the government to decriminalise the growing and consumption of marijuana for medical purposes.
But the most recent World Drug Report shows, where the cannabis plant and products are sold for medical use, recreational consumption also rises.
The best figures available are those for the United States, even in jurisdictions where all use and possession of the drug is still banned.
Angela Me heads the research and trend-analysis branch at the United Nations Office on Drugs and Crime.
"Yes, since about 2007, you definitely see a spike, a drastic change in all indicators relating to cannabis, that really shows how the cannabis market has expanded since then."
The United Nations says the main reason is people in the United States now perceive marijuana to be less harmful than they once did.
Angela Me says the decriminalisation, the acceptance of medical use and the debate in the media have contributed to more people feeling it is okay to use marijuana.
And, to use it more often.
"We see that, also, those who have access to medical marijuana -- some where they actually need the medication for a certain condition-- but that some also use it for recreational. So, in a way, it is misused, the access to medical marijuana, for recreational purposes."
She says the United Nations worries that the United States has gone too far with its decriminalisation.
"Typically, they have a system by which people register, where a doctor certifies that a person is in need of medical marijuana because of a certain condition, and then this person has access to any type, any quantity and any form. Medical marijuana in the United States in those states (that legalise it) is just opened up to buy cannabis in any form."
Among those presenting the petition urging the Austrian parliament to liberalise marijuana laws is a man named Patrick Krammer.
He is wheelchair-bound and receiving treatment for chronic pain.
"Yes, it's painful, very painful, especially the nerve pain. I compare it to ... if one is rubbing stinging nettles all over the skin, that's what the nerve pain is like."
Mr Krammer's medication is expensive, and he says he wants the government to let people in his condition grow their own marijuana and use it for pain relief.
But it is not clear if the petitioners' demands will be met.
Erwin Rasinger is the health spokesman for the Austrian People's Party -- and a doctor as well.
He seems sympathetic.
"Yes, cannabis is everything. It can be a sedative for a stressed manager. For the young, it can be a powerful drug. For me, as a doctor, it can be a therapy, a very good medicine."
The United Nations is monitoring the effects of decriminalisation in the United States and other parts of the world.
But it is too early to tell if increased use is causing a rise in what are called "cannabis-use disorders."
Angela Me says the UN position is cannabis-derived drugs have a place in medicine but the international conventions on drugs should be applied.
"It is in the spirit of the convention that countries give access to controlled substances for medical use. But, again, this medical use needs to be scheduled, it needs to be controlled, to make sure that there is not a spillover in actually increasing recreational use."
