How many people have schizophrenia?
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A 2005 review of prior surveys in 46 countries on the prevalence of schizophrenic disorders, including a prior 10-country WHO survey, found an average (median) figure of 0.4% for lifetime prevalence up to the point of assessment and 0.3% in the 12-month period prior to assessment. A related figure not given in other studies (known as lifetime morbid risk), reported to be an accurate statement of how many people would theoretically develop schizophrenia at any point in life regardless of time of assessment, was found to be "about seven to eight individuals per 1,000" (0.7/0.8%). The prevalence of schizophrenia was consistently lower in poorer countries than in richer countries (though not the incidence), but the prevalence did not differ between urban/rural areas or men/women (although incidence did).
Prevalence of mental disorders
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Schizophrenia affects around 0.3–0.7% of people at some point in their life, or 21 million people worldwide as of 2011 (about one of every 285). By using precise methods in its diagnosis and a large, representative population, schizophrenia seems to occur with relative consistency over time during the last half-century.
Epidemiology of schizophrenia
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Schizophrenia has great human and economic costs. It results in a decreased life expectancy by 10–25 years. This is primarily because of its association with obesity, poor diet, sedentary lifestyles, and smoking, with an increased rate of suicide playing a lesser role. Antipsychotic medications may also increase the risk. These differences in life expectancy increased between the 1970s and 1990s.
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. Approximately three-fourths of people with schizophrenia have ongoing disability with relapses and 16.7 million people globally are deemed to have moderate or severe disability from the condition. Some people do recover completely and others function well in society. Most people with schizophrenia live independently with community support. About 85% are unemployed. Some evidence suggests that paranoid schizophrenia may have a better prospect than other types of schizophrenia for independent living and occupational functioning. In people with a first episode of psychosis a good long-term outcome occurs in 42%, an intermediate outcome in 35% and a poor outcome in 27%. Outcomes for schizophrenia appear better in the developing than the developed world. These conclusions have been questioned.
There is a higher than average suicide rate associated with schizophrenia. This has been cited at 10%, but a more recent analysis revises the estimate to 4.9%, most often occurring in the period following onset or first hospital admission. Several times more (20 to 40%) attempt suicide at least once. There are a variety of risk factors, including male gender, depression, and a high intelligence quotient.
Schizophrenia and smoking have shown a strong association in studies worldwide. Use of cigarettes is especially high in those diagnosed with schizophrenia, with estimates ranging from 80 to 90% being regular smokers, as compared to 20% of the general population. Those who smoke tend to smoke heavily, and additionally smoke cigarettes with high nicotine content. Some propose that this is in an effort to improve symptoms. Among people with schizophrenia use of cannabis is also common.
Schizophrenia
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People with schizophrenia often have additional mental health problems such as anxiety, depressive, or substance-use disorders. Schizophrenia occurs along with obsessive-compulsive disorder (OCD) considerably more often than could be explained by chance. An estimated 21% to 47% of patients with schizophrenia have a substance misuse disorder at some time in their life, and the chances of developing a substance misuse disorder is significantly higher among patients suffering from a psychotic illness. All of these factors result in an increased range of clinical presentations and suggest a significant etiological heterogeneity.
Diagnosis of schizophrenia
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Media coverage relating to violent acts by people with schizophrenia reinforces public perception of an association between schizophrenia and violence. In a large, representative sample from a 1999 study, 12.8% of Americans believed that those with schizophrenia were "very likely" to do something violent against others, and 48.1% said that they were "somewhat likely" to. Over 74% said that people with schizophrenia were either "not very able" or "not able at all" to make decisions concerning their treatment, and 70.2% said the same of money-management decisions. The perception of people with psychosis as violent has more than doubled in prevalence since the 1950s, according to one meta-analysis.
Schizophrenia
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In support of the above mentioned conclusions many studies have been performed. Doctors Lindamer, Lohr, Harris, and Jeste conducted a study to determine age of onset of schizophrenia in which they examined gender differences in 194 patients ranging in age from 35 to 97. They found that the mean age for onset in men was 30, while in women it was 39. (It is important to note that this is just one study, and overall averages come from a combination of different studies). About 37% of the women developed schizophrenia at the age of 45, while only 16% of men reported the same. Thus, more women than men experience late onset schizophrenia. This indicates that there is indeed another peak for women at the age of 45 and women do develop schizophrenia later in life.
Effects of estrogen on schizophrenia
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Schizophrenia is a complex disorder that affects about a half percent of the world's population. Typically, the first symptoms of schizophrenia typically appear in adolescence. In a genome-wide association study of 1,735 schizophrenic patients and 3,485 healthy adults, the Center identified copy number variations as a potential cause of the disorder. In the schizophrenia group, researchers located CNVs near the CACNA1B and DOC2A genes, both of which facilitate calcium signals that are important to neurotransmission in the brain. They also identified CNVs near the RET and RIT2 genes, which are known to be involved in brain development. Some of the regions associated with schizophrenia have previously been found to associate with autism and ADHD. This provides a strong indication that many psychiatric disorders stem share similar neurodevelopmental features.
Center for Applied Genomics
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It is possible for schizophrenia to develop at any age, but it mostly happens to people within the ages of 16–30 (generally males aged 16–25 years and females 25–30 years); about 75 percent of people living with the illness developed it in these age-ranges. There is a likelihood of children developing schizophrenia, though it is quite rare before the age 12. Also, new cases are uncommon after age 40. In addition, about 1 percent of the world's population will develop schizophrenia over their lifetime, therefore out of all the people born, 1 in 100 will develop schizophrenia by age 55. There is on average a somewhat earlier onset for men than women, with the possible influence of the female sex hormone estrogen being one hypothesis and socio-cultural influences another.
Causes of schizophrenia
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In the first half of the 20th century schizophrenia was considered to be a hereditary defect, and sufferers were subject to eugenics in many countries. Hundreds of thousands were sterilized, with or without consent—the majority in Nazi Germany, the United States, and Scandinavian countries. Along with other people labeled "mentally unfit", many diagnosed with schizophrenia were murdered in the Nazi "Action T4" program.
History of schizophrenia
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In 2000, 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 100,000 ranging from 343 in Africa to 544 in Japan and Oceania for men, and from 378 in Africa to 527 in Southeastern Europe for women. About 1.1% of adults have schizophrenia in the United States.
Schizophrenia