Legalizing Marijuana: Putting the Cart Before the Horse?

More Research Desperately Needed, Experts Say

Fran Lowry

December 10, 2012

AVENTURA, Florida — The recent legalization of marijuana for nonmedical use in the states of Colorado and Washington sends a misleading message that it is safe, when in fact the true risks and benefits of cannabis have not been adequately evaluated, experts say.

Dr. Reetta Marciano

In research presented here at the American Academy of Addiction Psychiatry (AAAP) 23rd Annual Meeting & Symposium, scientists led by Reetta Marciano, MD, from the University of Maryland, in Baltimore, told delegates that cannabis has not been assessed by the US Food and Drug Administration (FDA) and that controlled trials of the drug are desperately needed.

"We have other drugs out there that have not been FDA-approved per se, such as alcohol, but when people use alcohol, they know what the side effects are. When they use marijuana, in many cases they have no idea what the risks and benefits are, and that is concerning," Dr. Marciano told Medscape Medical News.

"Our study group felt that it was necessary to highlight the risks, not just for the general public but also for the medical profession," she said.

Known Risks

Dr. Marciano and her team did an extensive PubMed search and selected 106 of the most pertinent studies that were published in peer-reviewed journals.

They found that multiple adverse effects of cannabis were described in the literature, including psychological impairment, T-cell suppression, stimulated growth of certain cancers, and hepatic steatosis and fibrosis.

In the brain, the literature showed that cannabis use was associated with psychosis in susceptible individuals, impaired attention, smaller hippocampal regions and frontotemporal white matter volumes, dose-dependent neuropathologic effects in the cerebellum, and bithalamic volume loss.

Maternal cannabis use during pregnancy was shown to alter pain regulation in the neonate and also to reduce the number of T-cells, thereby predisposing the infant to increased risk for infection. It also reduced foot length and impaired brain development.

With regard to cancer, cannabis was associated with the growth of breast, lung, and head and neck cancers, and a possible decrease in colon cancer.

Also, studies showed that tetrahydrocannabinol (THC) is a cytochrome P450 substrate and an inhibitor causing concern for drug interactions. It can lead to adverse interactions when paired with a variety of medications, including warfarin, indomethacin, and fluoxetine.

The review also showed that cannabis may be effective for chronic pain but that it was ineffective for acute pain.

"I would like to see more controlled studies on cannabis and its side effects so that we can with good conscience tell people what it does and doesn't do and what medications it interferes with," Dr. Marciano said.

Decriminalization the Intent

Commenting on this study for Medscape Medical News, Seth Flesher, MD, from St. Luke's-Roosevelt Hospital, New York City, said that the decision to legalize marijuana in some states stems from the desire to decriminalize its use.

"I believe that one of the reasons cannabis has been legalized has been due to the feeling that criminalizing it has its own side effects. The cost to society of people having jail records and not being able find work, being separated from their families, and the financial stress of enforcement in this era of government austerity trumped the possible dangers of cannabis."

He agreed with the study authors that people need to be aware of possible adverse effects associated with cannabis.

"There is no drug that does not have side effects. Some people used to think that cannabis was harmless, but I don't think anyone still believes that. People need to be aware that cannabis does have side effects. Anytime you put something into your body that is not naturally there, you should know as much about what that substance might do as possible."

Dr. Marciano and Dr. Flesher have disclosed no relevant financial relationships.

American Academy of Addiction Psychiatry (AAAP) 23rd Annual Meeting & Symposium. Abstract 12. Presented December 7, 2012.