As of 2015, four states have legalized medical and recreational marijuana, including Colorado, Oregon, Washington and Alaska, according to Governing.com. Several states have legalized medical marijuana, including California, Illinois, New York, New Jersey and Maine. Washington D.C. also permits residents to possess small quantities of marijuana.
Research shows that marijuana is effective in treating some chronic illnesses and also helps patients deal with nausea, vomiting and a lack of appetite, states Health.com. Marijuana also helps patients ease their pain. Most states charge a fee to get a medical marijuana license and impose limits on how much patients can possess. For example, patients in California can possess 8 ounces and 16 plants and must pay $33 to $66 for a license.