Schizophrenia is a severe disorder that alters aspects of normal mental health such as the ability to distinguish reality from fantasy and the ability to exhibit appropriate emotional and social responses to a given situation. People affected by the disorder often have debilitating degrees of mental and social impairment. Statistically speaking, schizophrenics smoke marijuana much more frequently than people without the disorder, and current evidence indicates that marijuana use can create changes in the brain that predispose certain individuals toward the development of schizophrenia. In many (if not most) cases, affected individuals appear to have known or unknown genetic schizophrenic tendencies. Schizophrenia Basics Schizophrenia is really a general term for a group of disorders that seriously alter normal mental function, the US National Library of Medicine explains. People with a condition called paranoid schizophrenia develop problems that commonly include anxiety, unpredictable anger, and a delusional belief in the hostile intentions of others. People with a condition called catatonic schizophrenia develop problems that commonly include social unresponsiveness, muscle rigidity, unusual body immobility, and abnormal or unusual facial expressions. People with a condition called disorganized schizophrenia have typical problems that include a lack of emotional expressiveness, convoluted or hard-to-decipher thought patterns, and age-inappropriate social behaviors. Other problems frequently found in schizophrenics include visual and\/or auditory (sound-related) hallucinations, suicidal thoughts or actions, depression, and an inability to focus on ongoing reality. Some people have a form of the disorder called undifferentiated schizophrenia, which produces unique combinations of symptoms from two or more types of schizophrenia. People with schizophrenia develop distinct changes in their brains, according to a study published in 2010 in the journal Pharmaceuticals. Among these changes is an increase in the number of specialized sites, called endocannabinoid receptors, on the surfaces of nerve cells (neurons) located in several different brain areas. These sites provide neuron access for a variety of naturally occurring chemicals in the brain, called endocannabinoids, which alter human mood and memory, as well as the perception of pain and appetite. Schizophrenics also experience an unusual increase in their levels of anandamide, the body\u2019s most prominent endocannabinoid chemical. Effects of Marijuana Use The main active ingredient in marijuana, known as tetrahydrocannabinol or THC, achieves its effects by accessing the same endocannabinoid receptors used by anandamide and other naturally occurring endocannabinoid chemicals. When THC accesses the endocannabinoid receptors, it produces subtle changes in the normal synchronization of activity in certain parts of the brain, the authors of a study published in 2011 in the Journal of Neuroscience report. Specific areas of the brain affected by this altered synchronization include structures called the hippocampus and the prefrontal cortex, which play key roles in such basic brain functions as rational thinking, judgment and memory. In people with schizophrenia, increased numbers of endocannabinoid receptors form in both the hippocampus and the prefrontal cortex, and doctors believe that receptor-related changes in these areas play a significant part in the onset of schizophrenia\u2019s symptoms. According to the authors of the study published in the Journal of Neuroscience, THC\u2019s effects on the prefrontal cortex and hippocampus also produce schizophrenia-like symptoms in the form of a limited version of psychosis (a term used to describe the presence of delusional thinking and\/or hallucinations). These effects may explain a phenomenon in marijuana users known as \u201ctemporal disintegration,\u201d which occurs when the brain temporarily loses its ability to properly store, organize, or refer to certain memories and perceptions. In a study published in 2012 in the journal Frontiers in Psychiatry, researchers from Norway\u2019s University of Bergin examined the differences between the brains of schizophrenics with a history of marijuana use and the brains of schizophrenics who have never used the drug. They concluded that marijuana-using schizophrenics show evidence of a weakening in basic mental function not found in non-marijuana-using schizophrenics. The authors of the study also concluded that this weakening of mental function produces schizophrenia-like psychosis in otherwise healthy marijuana users. Genetic Biases According to the findings of a study released in 2010 by France\u2019s National Institute of Health and Medical Research, a real-world link between marijuana use and true, diagnosable schizophrenia may only occur in people with preexisting recognized or unrecognized genetic tendencies for developing the disorder. When these people use marijuana, they may hasten the onset of schizophrenic symptoms by as much as three years. In addition, the authors of the study note, people with genetic susceptibilities to schizophrenia frequently start smoking marijuana at an earlier age than their peers; in turn, this early use of the drug may further bias the brain toward the functional alterations that eventually lead to active schizophrenia.