When Cheech and Chong lit up the movie screens with their marijuana-fogged dialogue - "Hey man, how's my driving?" "I think we're parked, man" - they probably never imagined cannabis would become legal. But today more than 20 states have authorized medical marijuana, while Colorado and Washington have legalized it for personal use. So we say it's time to back up (carefully) and take a look at the health risks associated with recreational use (addressing medical use is for another column).

The active ingredient in marijuana (THC or 9 delta-9-tetrahydrocannabinol) has been engineered to be much more concentrated in today's crops than it was in the 1970s. That, combined with the highly individual way the drug affects the brain (20-somethings, listen up, you're still developing neural wiring), makes it hard to predict who might be at risk for long-term marijuana-related problems.

What is known, according to the National Institute on Drug Abuse, is that regular or heavy use is linked to traffic accidents and reduced lung function (the smoke contains carcinogens) and can encourage addictions. In addition, for some folks, THC's effect on neurotransmitters may increase the risk for depression and the development of psychosis. It also can cause memory and attention deficits. And particular to eating THC, there may be an increased risk of panic or anxiety.

Our advice? Go for a free twofer: An exercise high from aerobic routines, like interval walking (see doctoroz.com for how-to), boosts both serotonin and endorphin levels. You'll get smokin' hot without craving a peanut butter and jelly pizza.