“When we opened … the younger people were coming in and we were like, ‘Come back when you’re this tall,’ ” said Ms. MacLellan, a 55-year-old former police officer. “The people coming in daily now, they’re all white hairs.”

Her customers reflect a subtle demographic shift in marijuana users nationwide that anecdotal evidence suggests is a blend of medicinal and social needs.

The 2012 Canadian Community Health Survey released last week showed that 6.7 per cent of adults between the ages of 45 and 64 used the drug in the last year, up from 4.3 per cent in 2002. Among adults over 65, the percentage of users quadrupled over the same period, to 0.8 per cent from 0. 2 per cent.

To put those figures in perspective, the number of Canadians over 45 who reported using marijuana in the previous year doubled to 687,511 from 338,407 over the last 10 years. By contrast, the number of marijuana users under the age of 45 dipped slightly, with the biggest drop coming from the age group of 15 to 24 years old.

Craig Jones, spokesman for the National Organization for the Reform of Marijuana Laws in Canada, said the statistics reflect a trend among baby boomers who are discovering medicinal benefits in a drug they used socially in their youth.

“For some older people, they never bought into the hysteria, the reefer madness, and they circled back to it because they enjoyed the experience, the side effects as they call it, and it’s an easily tolerated analgesic for chronic non-malignant pain,” Mr. Jones said.

Other users never stopped indulging as they aged and now use the drug for recreational and medical purposes. “I have some arthritis in the back of my neck and I use it when I’m having bad days to reduce inflammation,” said Lee Russell, a 53-year-old vinyl-sign installer from Winnipeg. “And then comes the weekends.”

When the seeds of the federal medical-marijuana program were planted in 2001, a few hundred people were authorized to use the drug. Today, the government is struggling to rein in the lawful distribution of marijuana after Health Canada acknowledged the number of program participants had swelled to more than 30,000.

Alison Myrden, 49, a multiple sclerosis patient from Burlington, Ont., became a poster child for the medical marijuana movement when she smoked a joint at a Parliament Hill news conference in 2003. An advocate for decriminalizing the drug, Ms. Myrden theorized that the movement has dampened youthful enthusiasm for pot. “Since people like myself came out and said we use it for medicine, it doesn’t seem to be as much fun for the kids anymore,” she said.