Marijuana is the most commonly used illegal drug in America: approximately one in 10 adult Americans report having used marijuana in the past year. In recent years, laws addressing the use and possession of marijuana have been changing, and many states—including Colorado, California, Massachusetts and others—have passed regulations either legalizing marijuana for medical purposes or decriminalizing the non-medical use of marijuana. While different groups of professionals have had varied responses to the implications of this new legislation, mental health professionals have been largely united in expressing their concerns of the negative impact marijuana has for people with mental illness. Furthermore, the scientific data is clear that regular marijuana abuse is linked with increased risk of legal troubles and jail time, difficulties at school and at work, as well as abuse of alcohol and other drugs.