Many important brain functions which affect human behavior involve the neurotransmitter dopamine. Serious drugs of abuse, such as heroin and cocaine, interfere with the brain’s use of dopamine in manners that can seriously alter an individual’s behavior. A drug’s ability to affect the neural systems related to dopamine production has now become the defining characteristic of drugs with serious abuse potential. According to the congressional Office of Technology Assessment, research over the last 10 years has proved that marijuana has no effect on dopamine-related brain systems. The dominant fear about marijuana in the 20th century has been that its effects were somehow similar to the dangerously addictive effects of opiates such as morphine and heroin. Marijuana also affects receptors in brain areas and structures responsible for sensory perception. Marijuana interferes with the receiving of sensory messages (for example, touch, sight, hearing, taste, and smell) in the cerebral cortex (Gettman 42). Recent research in animals has also suggested that long-term use of marijuana (THC) produces changes in the limbic system that are similar to those that occur after long-term use of other major drugs of abuse such as cocaine, heroin, and alcohol. These changes are most evident during withdrawal from THC. During withdrawal, there are increases in both the levels of a brain chemical involved in stress and certain emotions. These same kinds of changes also occur during withdrawal from other drugs of abuse, suggesting that there may be a common factor in the development of drug dependence. It is obvious that marijuana is an illegal drug that has its affects on the brain. For that reason it is very important that we do not ignore the face that it is being abused and seen a lot more lightly than other drugs that are said to have a more dangerous affect on our minds and bodies. It is clear that throughout research there has been beneficial factors to the use of marijuana for medical purposes but that is not to say that it is okay use to try to “prevent illness” because as good as that may sound it is unrealistic and still illegal. Marijuana is dried leaves and flowers from a cannabis plants that, when taken into the human body allow people to experience a calm called euphoria. But one has to wonder if a few moments of euphoria is worth a lifetime of damage to the brain.