“What’s really going on here is that over the last 20 years marijuana went from being used like alcohol to being used more like tobacco, in the sense of lots of people using it every day.” So said Jonathan Caulkins, co-author of a recent study on marijuana use, in a Washington Post article. One in three people who said they’d used pot at all in the past month said they used it daily, his study found — up from one in nine in the early ’90s.

The ratio of marijuana arrests to marijuana purchases fell by nearly half from 2002 to 2013, according to the study. The study period preceded the dawn of lawful recreational pot in Colorado, but it did include some liberalization of marijuana policy. The authors say their work could help inform the policy debate.

Perhaps. But it should also prompt us to remember that good policy and good advice are two different things.

Even if marijuana should be less restricted, even if it should be completely unrestricted, that does not mean that you should use it. As decriminalization is debated, we need to consider questions such as whether using pot harms people around you and whether it’s worth putting people in prison over. When we discuss actually using it, we need to ask whether using it — or using it with any particular frequency — is good for you. It’s perfectly possible for something to be bad for you and none of the government’s business. Imagine eating nothing but ice cream for breakfast, lunch and dinner.

Substances that affect the mind need to be handled with care. That’s true of psychiatric medications, which require the careful attention of both doctor and patient. It’s true of alcohol. And it’s true of marijuana.

First Published: September 13, 2016, 4:00 a.m.