Different terminology is used, but a dimension for hallucinations, a dimension for disorganization, and a dimension for negative symptoms are usually described. Deficits in cognitive abilities are widely recognized as a core feature of schizophrenia. Verbal memory impairment has been linked to a decreased ability in those with schizophrenia to semantically encode process information relating to meaning , which is cited as a cause for another known deficit in long-term memory.
Although the evidence that cognitive deficits remain stable over time is reliable and abundant,   much of the research in this domain focuses on methods to improve attention and working memory. Late adolescence and early adulthood are peak periods for the onset of schizophrenia,  critical years in a young adult's social and vocational development. A combination of genetic and environmental factors play a role in the development of schizophrenia.
Lundbeck Initiates Phase II Study of Potential New Treatment of Schizophrenia
Many genes are known to be involved in schizophrenia, each of small effect and unknown transmission and expression. The question of how schizophrenia could be primarily genetically influenced, given that people with schizophrenia have lower fertility rates, is a paradox. It is expected that genetic variants that increase the risk of schizophrenia would be selected against due to their negative effects on reproductive fitness. A number of potential explanations have been proposed, including that alleles associated with schizophrenia risk confers a fitness advantage in unaffected individuals.
Environmental factors associated with the development of schizophrenia include the living environment, drug use, and prenatal stressors. Maternal stress has been associated with an increased risk of schizophrenia, possibly in association with reelin. Both maternal stress and infection have been demonstrated to alter fetal neurodevelopment through pro-inflammatory proteins such as IL-8 and TNF. Parenting style seems to have no major effect, although people with supportive parents do better than those with critical or hostile parents.
It has been hypothesized that in some people, development of schizophrenia is related to intestinal tract dysfunction such as seen with non-celiac gluten sensitivity or abnormalities in the intestinal flora. About half of those with schizophrenia use drugs or alcohol excessively.
Alcohol abuse can occasionally cause the development of a chronic, substance-induced psychotic disorder via a kindling mechanism. Cannabis may be a contributory factor in schizophrenia , potentially causing the disease in those who are already at risk. Other drugs may be used only as coping mechanisms by people who have schizophrenia, to deal with depression, anxiety, boredom, and loneliness.
Factors such as hypoxia and infection, or stress and malnutrition in the mother during fetal development , may result in a slight increase in the risk of schizophrenia later in life. While the mechanism of schizophrenia is unknown, a number of attempts have been made to explain the link between altered brain function and schizophrenia. Frameworks have hypothesized links between these biological abnormalities and symptoms. Abnormal dopamine signalling has been implicated in schizophrenia based on the usefulness of medications that effect the dopamine receptor and the observation that dopamine levels are increased during acute psychosis.
Reduced NMDA receptor signalling is suggested by multiple lines of evidence.
Studies demonstrate reduced NMDA receptor expression and NMDA receptor blockers mimic both schizophrenia symptoms and the physiological abnormalities associated with schizophrenia. Both working memory tasks and gamma oscillations are impaired in schizophrenia, which may reflect abnormal interneuron functionality.
Evidence suggest that schizophrenia has a neurodevelopmental component. Before the onset of schizophrenia there is often impairments in cognition, social functioning, and motor skills.
Deficits in executive functions , such as planning, inhibition, and working memory , are pervasive in schizophrenia. Although these functions are dissociable, their dysfunction in schizophrenia may reflect an underlying deficit in the ability to represent goal related information in working memory, and to utilize this to direct cognition and behavior. For example, functional neuroimaging studies report evidence of reduced neural processing efficiency, whereby the dorsolateral prefrontal cortex is activated to a greater degree to achieve a certain level of performance relative to controls on working memory tasks.
These abnormalities may be linked to the consistent post-mortem finding of reduced neuropil , evidenced by increased pyramidal cell density and reduced dentritic spine density.
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These cellular and functional abnormalities may also be reflected in structural neuroimaging studies that find reduced grey matter volume in association with deficits in working memory tasks. Positive and negative symptoms have been linked to reduced cortical thickness in the superior temporal lobe,  and orbitofrontal cortex , respectively. However, a large body of evidence suggests that hedonic responses are intact in schizophrenia,  and that what is reported to be anhedonia is a reflection of dysfunction in other processes related to reward.
Bayesian models of brain functioning have been utilized to link abnormalities in cellular functioning to symptoms. In canonical models of circuits that mediate predictive coding, hypoactive NMDA receptor activation, similar to that seen in schizophrenia, could theoretically result in classic symptoms of schizophrenia such as delusions and hallucinations. These criteria use the self-reported experiences of the person and reported abnormalities in behavior, followed by a clinical assessment by a mental health professional.
Symptoms associated with schizophrenia occur along a continuum in the population and must reach a certain severity and level of impairment before a diagnosis is made.
Schizophrenia - American Family Physician
To be diagnosed with schizophrenia, two diagnostic criteria have to be met over much of the time of a period of at least one month, with a significant impact on social or occupational functioning for at least six months. The person had to be suffering from delusions, hallucinations, or disorganized speech. A second symptom could be negative symptoms, or severely disorganized or catatonic behaviour. The ICD criteria are typically used in European countries; the DSM criteria are used in the United States and some other countries, and are prevailing in research studies.
The ICD criteria put more emphasis on Schneiderian first-rank symptoms. In practice, agreement between the two systems is high.
If signs of disturbance are present for more than a month but less than six months, the diagnosis of schizophreniform disorder is applied. Psychotic symptoms lasting less than a month may be diagnosed as brief psychotic disorder , and various conditions may be classed as psychotic disorder not otherwise specified ; schizoaffective disorder is diagnosed if symptoms of mood disorder are substantially present alongside psychotic symptoms. If the psychotic symptoms are the direct physiological result of a general medical condition or a substance, then the diagnosis is one of a psychosis secondary to that condition.
The ICD defines additional subtypes: . Psychotic symptoms may be present in several other mental disorders, including bipolar disorder ,  borderline personality disorder ,  drug intoxication, and drug-induced psychosis. Delusions "non-bizarre" are also present in delusional disorder , and social withdrawal in social anxiety disorder , avoidant personality disorder and schizotypal personality disorder.
Schizotypal personality disorder has symptoms that are similar but less severe than those of schizophrenia. It can resemble schizophrenia and be misdiagnosed as such. A more general medical and neurological examination may be needed to rule out medical illnesses which may rarely produce psychotic schizophrenia-like symptoms, such as metabolic disturbance , systemic infection , syphilis , AIDS dementia complex , epilepsy , limbic encephalitis , and brain lesions.
Stroke , multiple sclerosis , hyperthyroidism , hypothyroidism , and dementias such as Alzheimer's disease , Huntington's disease , frontotemporal dementia , and the Lewy body dementias may also be associated with schizophrenia-like psychotic symptoms. Investigations are not generally repeated for relapse unless there is a specific medical indication or possible adverse effects from antipsychotic medication. In children hallucinations must be separated from typical childhood fantasies.
Prevention of schizophrenia is difficult as there are no reliable markers for the later development of the disorder. The primary treatment of schizophrenia is antipsychotic medications, often in combination with psychological and social supports.
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Long-term hospitalization is uncommon since deinstitutionalization beginning in the s, although it still occurs. Some evidence indicates that regular exercise has a positive effect on the physical and mental health of those with schizophrenia. The first-line psychiatric treatment for schizophrenia is antipsychotic medication,  which can reduce the positive symptoms of psychosis in about 7 to 14 days.
Antipsychotics fail to significantly improve the negative symptoms and cognitive dysfunction. The choice of which antipsychotic to use is based on benefits, risks, and costs. Most people on antipsychotics have side effects. People on typical antipsychotics tend to have a higher rate of extrapyramidal side effects ; some atypicals are associated with considerable weight gain, diabetes and risk of metabolic syndrome.
This is most pronounced with olanzapine; risperidone and quetiapine are also associated with weight gain. For people who are unwilling or unable to take medication regularly, long-acting depot preparations of antipsychotics may be used to achieve control. A number of psychosocial interventions may be useful in the treatment of schizophrenia including: family therapy ,  assertive community treatment , supported employment, cognitive remediation ,  skills training, token economic interventions, and psychosocial interventions for substance use and weight management.
Schizophrenia has great human and economic costs. Schizophrenia is a major cause of disability , with active psychosis ranked as the third-most-disabling condition after quadriplegia and dementia and ahead of paraplegia and blindness. There is a higher than average suicide rate associated with schizophrenia.
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- Medical Illness and Schizophrenia.
Schizophrenia and smoking have shown a strong association in studies worldwide. Schizophrenia affects around 0. Despite the prior belief that schizophrenia occurs at similar rates worldwide, its frequency varies across the world,   within countries,  and at the local and neighborhood level.
In , the World Health Organization found the percentage of people affected and the number of new cases that develop each year is roughly similar around the world, with age-standardized prevalence per , ranging from in Africa to in Japan and Oceania for men, and from in Africa to in Southeastern Europe for women.
Medical Illness and Schizophrenia
In the early 20th century, the psychiatrist Kurt Schneider listed the forms of psychotic symptoms that he thought distinguished schizophrenia from other psychotic disorders. These are called first-rank symptoms or Schneider's first-rank symptoms. They include delusions of being controlled by an external force, the belief that thoughts are being inserted into or withdrawn from one's conscious mind, the belief that one's thoughts are being broadcast to other people, and hearing hallucinatory voices that comment on one's thoughts or actions or that have a conversation with other hallucinated voices.
A review of the diagnostic studies conducted between and found that they allow neither a reconfirmation nor a rejection of Schneider's claims, and suggested that first-rank symptoms should be de-emphasized in future revisions of diagnostic systems. The history of schizophrenia is complex and does not lend itself easily to a linear narrative. A detailed case report in concerning James Tilly Matthews , and accounts by Philippe Pinel published in , are often regarded as the earliest cases of the illness in the medical and psychiatric literature.
In Emil Kraepelin borrowed the term from Schule and Pick and in introduced a broad new distinction in the classification of mental disorders between dementia praecox and mood disorder termed manic depression and including both unipolar and bipolar depression.