Which neurotransmitter(s) was/were the first to be linked with schizophrenia?
What are the symptoms of schizophrenia?The behavior of people with schizophrenia is often very strange and shocking. This change in behavior, when people cannot tell the difference between what is real and what is not, is called "psychosis" or a "psychotic episode." The American Psychiatric Association has published guidelines that are used to classify people with mental disorders. The most recent guidelines are contained in a book called the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (known as DSM-5 for short). The DSM-5 describes several symptoms that a person MUST have before he or she is classified as having schizophrenia. These symptoms include two or more of the following behaviors for a duration of at least one month:
When people show any of these five symptoms, they are considered to be in the "active phase" of the disorder. Often people with schizophrenia have milder symptoms before and after the active phase. There are three basic types of schizophrenia. All people who have schizophrenia have lost touch with reality. The three main types of schizophrenia are:
What occurs in the brain?A common finding in the brains of people with schizophrenia is larger than normal lateral ventricles. The lateral ventricles are part of the ventricular system that contains cerebrospinal fluid.The picture below shows magnetic resonance image (MRI) brain scans of a pair of twins: one with schizophrenia, one without schizophrenia. Notice that the ventricles (red arrows) are larger in the twin with schizophrenia. (Image courtesy of NIMH Clinical Brain Disorders Branch.)
A reduced size of the hippocampus, increased size of the basal ganglia, and abnormalities in the prefrontal cortex are seen in some people with schizophrenia. However, these changes are not seen in all people with schizophrenia and they may occur in people without this disorder. What are the causes of schizophenia?There are probably multiple causes for schizophrenia and scientists do not know all of the factors that produce this mental disorder.GeneticsSchizophrenia does "run in the family." In other words, schizophrenia has an important genetic component. Evidence for a genetic component comes from twin studies. Monozygotic twins (identical twins) are those with exactly the same genetic makeup; dizygotic twins (fraternal twins) are those who share only half of their genetic makeup. If genetics was the ONLY factor in developing schizophrenia, then both monozygotic twins should always develop this illness.Twin StudiesTwin studies have shown that the tendency for both monozygotic (identical) twins to develop schizophrenia is between 30-50%. The tendency for dizygotic (fraternal) twins to develop schizophrenia is about 15%. The tendency for siblings who are not twins (such as brothers of different ages) is also about 15%. Remember, schizophrenia is found in the general population at a rate of about 1%. Therefore, because the tendency for monozygotic twins is NOT 100%, genetics cannot be the only factor. However, because the tendency for monozygotic twins to have schizophrenia is much greater than the tendency for dizygotic twins, genetics DOES play a role.
Adoption StudiesSome studies have looked at the family background of people who were adopted at an early age and who later developed schizophrenia. One study (Kety et al., 1968) found that 13% of the biological relatives of the adoptees with schizophrenia also had schizophrenia, but only 2% of the relatives of "normal" adoptees had schizophrenia. These studies support the role of genetics in schizophrenia.To learn more about the role of genetics in schizophrenia, see the Genetics and Mental Disorders page at the National Institute of Mental Health. EnvironmentNongenetic factors that may influence the development of schizophrenia include: family stress, poor social interactions, infections or viruses at an early age, or trauma at an early age. Somehow the genetic makeup of individuals combines with nongenetic (environmental) factors to cause schizophrenia.NeurotransmittersMany studies have investigated the possible role of brain neurotransmitters in the development of schizophrenia. Most of these studies have focused on the neurotransmitter called dopamine. The "dopamine theory of schizophrenia" states that schizophrenia is caused by an overactive dopamine system in the brain. There is strong evidence that supports the dopamine theory, but there are also some data that do not support it:Evidence FOR the Dopamine Theory of Schizophrenia:
Evidence AGAINST the Dopamine Theory of Schizophrenia:
Possible Side Effects of Antipsychotic Drugs
CounselingAntipsychotic medications often do not reduce all of the symptoms of schizophrenia. Also, because people with schizophrenia may have become ill during the time when they should have developed technical skills and a career, they may have difficulties working with other people. Therefore, psychological therapy, family therapy and occupational training may be used along with antipsychotic medication to help these people get back into the community.
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Which neurotransmitter imbalance occurs in a patient with schizophrenia?Research suggests schizophrenia may be caused by a change in the level of 2 neurotransmitters: dopamine and serotonin. Some studies indicate an imbalance between the 2 may be the basis of the problem.
When is the first episode of schizophrenia most likely to occur?The first episode of schizophrenia typically occurs in the late teenage years or the early 20s. However, the illness can remain undetected for about 2-3 years after the onset of clearly diagnosable symptoms.
Which of the following brain abnormalities is suggested to be a cause of schizophrenia?12 in the journal JAMA Psychiatry, builds on work at Yale that shows schizophrenia is associated with marked alterations in connections between the thalamus, a major relay system in the brain, and the frontal cortex, which is involved in higher-level cognitive functions.
What is dopamine overactivity most like?Given the tight correlation between the clinical potency and the D2-blocking action of the antipsychotic medications, dopamine overactivity could be the common denominator in the psychotic element of schizophrenia.
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