Schizophrenia is a mental disorder marked by the loss of contact with reality. Delusions, hallucinations, irregular thinking or emotions are the usual symptoms. About one hundred years ago schizophrenia was first recognized as a mental disorder and researchers have been searching for a cure since. The exact cause of schizophrenia is still unknown and scientists are certain that schizophrenia has more than one cause. Scientists have developed dozens of theories to explain what causes this disease, but researchers are focusing on three leading theories. The Genetic Theory argues that schizophrenia is caused by traits in a person’s genetic makeup. As we all know, a person has twenty-three pairs of chromosomes. Each pair contains one chromosome from each parent. In corresponding locations of each chromosome the genes for specific traits are located. If there are mutations or if there is the presence of an extra chromosome, genetic disorders occur. For example, Down Syndrome is caused by the presence of an extra 21st chromosome. It is believed that problems with the genetic make up can cause schizophrenia (Encarta 96). In an attempt to prove this theory scientists study identical twins. Due to the fact that identical twins have the exact genetic make up researchers will be able to determine if heredity is the main cause of schizophrenia. However, evidence seems to disprove this theory. This is because on some occasions both identical twins are schizophrenics and other times only one is inflicted. To defend the theory, it should be noted that this research is difficult and complicated. Identical twins are relatively rare, especially twins who are both diagnosed with schizophrenia. Further defending the theory, studies have shown that children with one parent diagnosed with schizophrenia have a ten percent chance of suffering from schizophrenia. When both parents are schizophrenic their risk raises to about fifty percent (468 Myers). The Biochemical theory is built mainly on stress that effects human behavior. However, most researchers agree that stress alone cannot be the main cause of schizophrenia. Most researchers agree that stress can trigger or worsen the symptoms when the illness is already present. Other researchers focus on drug abuse. Like stress, certain drugs such as amphetamines can make psychotic symptoms worse if a person already has schizophrenia. Also, amphetamines and other drugs cause an increase in dopamine. Brains of schizophrenics were found to contain an excess of receptors for dopamine (468 Myers). In one particular experiment, researchers injected animals with amphetamines, which causes an increase of dopamine in the brain. Following the injection, the animals exhibit the same behavior as humans who have been diagnosed with schizophrenia, such as standing still for long periods of time or continuously pacing. Nerve cells have an effect on schizophrenics as well. When something acts upon one of our senses, electrical impulses are sent to the brain. These impulses allow us to feel pain, smell, and also manage our thought processes. In our body we have a complex nerve system. For example, there is no one single nerve that travels from our feet to our brain. Therefore, in order for information to be sent to the brain the nerves must interact with each other. Because the system is so complex it is possible for the signal to get mixed up. When this happens, our brain may misinterpret the signal or may not receive it at all. If the signal does get mixed up on the way to the brain the make up of the impulse can undergo a chemical change resulting in abnormal thought processes and abnormal behavior (Smith). The Bio-Psycho-Social Theory combines all of the previous theories. Some researchers believe that biochemical abnormalities are a contributing factor but that other events must also occur. They suggest that environmental and social problems have to be considered along with biological problems. Social scientists believe that no chemical factors are involved, instead they believe “mental disorders are described as a consequence of human motivations, drives, and unconscious forces” (Smith). These scientists suggest that people become overloaded with stress, information, and stimulation. When this happens they lose their ability to cope with the anxiety which accompanies stress. Instead of dealing with their problems they seek peace in their own world. For example,