Expert-recommended warnings for medical marijuana.

Medical marijuana is legal in some countries, including in many US states. At present, there are no government-mandated warnings on packages of marijuana, even though the substance has dangers similar to those of alcohol, tobacco, and various prescribed drugs. This article reports the results of an effort to collect marijuana warnings recommended by scientific experts on marijuana. The recommended warnings, the first ever from marijuana experts, come from 13 experts. The expert-recommended warnings pertain to risks relating to (1) safety, (2) physical health, (3) fetal harm, (4) mental health, (5) withdrawal and dependence, and (6) adolescent development. The results provide initial expert recommendations for warnings to be required on packages of medical marijuana.