An overview of schizophrenia-related content on Genes to Cognition Online.

Symptoms of schizophrenia are divided into positive and negative categories. Positive refers to the marked presence of exaggerated processes, including disordered thoughts, delusions, and hallucinations. Negative symptoms refer to an absence or emotional flatness. Schizophrenia is a complex disorder that involves every level of the G2C spectrum. Candidate genes for the disorder include COMT, DISC1 and RGS4. These may interact with biochemicals including dopamine, serotonin, and glutamate, all of which have been associated with schizophrenia-like symptoms including hallucinations. From a cellular perspective, schizophrenia is caused by a failure of different regions of the brain to wire together correctly, causing the brain to lose coherence and coordination. Brain regions specifically associated with schizophrenia are numerous and include the hippocampus and prefrontal cortex. A number of environmental factors have been implicated including drug-use, toxins, and complicated pregnancies. GENES There is strong evidence that schizophrenia has a genetic component. If one identical twin develops the condition, the risk that the other will is 40-50%. For fraternal twins, on the other hand, the risk is approximately 10%. Use the chromosome Map of Disorders and Processes to explore some of the candidate genes associated with schizophrenia. Elsewhere on G2C Online Professors David Lewis and Judith Rapoport describe modern gene-finding techniques that are changing the way we understand the disorder. BIOCHEMICALS There are three primary biochemical hypotheses of schizophrenia – dopamine, serotonin, and glutamate, all of which are discussed by Professor Jeffrey Lieberman on G2C Online. The dopamine hypothesis is predominant drugs like cocaine, amphetamine, and methamphetamine produce schizophrenia-like behavioral effects and also stimulate the release of dopamine in the brain. Similarly, drugs such as LSD and ecstasy block serotonin and produce schizophrenia-like symptoms, including hallucinations. The same is true of the drug PCP, which acts on glutamate receptors. CELLS Schizophrenia is believed to develop because a certain group of genes affects the way specific neural circuits develop. These neural circuits affect higher thinking processes (how we form beliefs, how we perceive and interpret stimuli) and when these get disturbed, they become dysfunctional, and this produces the symptoms of schizophrenia. Schizophrenia is a neurodevelopmental disorder that arises because regions throughout the brain are not connected correctly and thereby lose their coherence and coordination. BRAIN Schizophrenia is not due to an abnormality in any single area of the brain. A series of video interviews with Professor David Lewis, Daniel Weinberger, and Nobel Laureate James Watson discuss some of the areas affected, which include the hippocampus and prefrontal cortex. COGNITION The Dana review text article, Schizophrenia – a Review, provides an overview of the key statistics relevant to schizophrenia. Worldwide prevalence is though to be approximately 1%. It usually appears in late adolescence or early adult life, and it tends to affect males more frequently and more severely than females. Professor Daniel Weinberger explains that schizophrenia has been called 'the cancer of mental illness' because of the severity of its impact. Symptoms of schizophrenia can be divided into positive and negative categories. Positive symptoms are mental functions that are exaggerated or distorted (e.g. hallucinations). Negative symptoms refer to diminished or absent emotions (flat affect). ENVIRONMENT A variety of different risk factors have been identified for schizophrenia, including birth during winter months (perhaps reflecting an exposure to an infection, either during fetal development or shortly after birth), exposure to such toxins as illegal drugs (particularly amphetamines), and a family history of the illness. You can read about these in the Dana review articles Preventing Schizophrenia and Schizophrenia – a Review.

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