The debate over whether to allow marijuana to be used for medicinal purposes has battles scattered over every state. While some cite the benefits of the drug for those who suffer from chronic pain from injury or from a serious disease like cancer, others believe that the benefits do not outweigh the risks. Marijuana has been linked to psychotic episodes in some research studies, and other aspects have not been fully explored to determine how marijuana use may impact certain aspects of life. For instance, the legalization of marijuana for medical use could impact driving restrictions and require new regulations. A recent study may slow the expansion of medical marijuana use in Arizona. Researchers from the University of Arizona, working with the Department of Health Services, which regulates the state's medical marijuana program, conducted a review of the studies documenting the effects of medical marijuana for the use of four medical conditions. The review considered the use of medical marijuana for the treatment of migraines, anxiety, post-traumatic stress disorder (PTSD) and depression. The review found little evidence that the use of marijuana was effective in treating the symptoms of these four conditions and could not be used to weigh the benefits versus the risks of medical marijuana. State health officials and supporters of the medical marijuana program both believe that the lack of scientific support for either side of the argument is largely due to restrictions on research involving controlled substances. Still, the review could impact efforts by advocates of the medical marijuana program to expand the program. While health officials have received dozens of testimonials about the effectiveness of medical marijuana and its impact on daily life, they stress that the program can only be expanded based on scientific evidence. State health director Will Humble explains that there must be ample evidence that the benefits outweigh the risks and the evidence does not exist. The Arizona Medical Marijuana Act maintains that the state health department must consider petitions to expand the program on a regular basis. Currently there are approximately 31,000 individuals enrolled in the medical marijuana program under conditions such as chronic pain or cancer. If the program were expanded to include the four conditions considered in the state's study, patients with PTSD would increase the program by as many as 15,000 individuals. Advocates for the program believe that marijuana is useful not only for treating chronic pain, but also for the psychological stress that can come with a mental illness. Many patients use marijuana after unsuccessfully trying all other medication possibilities. In the state of Arizona, officials insist that only scientific evidence will permit the expansion of the medical marijuana program. However, they are willing to consider evidence based on observational study designs, which are more easily conducted under the regulations imposed by the federal government.