Prevalence of Schizophrenia

Schizophrenia: 

  

Prevalence of Schizophrenia: 

The global prevalence of schizophrenia: 

 There is no doubt that the global burden of schizophrenia, a chronic serious mental illness, is massive. It is therefore essential that any intervention is appropriate, cost-effective, and efficacious. The prevalence rates of schizophrenia depend upon a whole range of factors, such as the availability of and response to treatment. The prevalence of schizophrenia, as with other mental disorders, can be calculated from a number of sources—from case registers to field surveys. The latter lend themselves more readily to estimation of period prevalence than point prevalence, while case register data can provide point prevalence more readily. The denominator can be the whole population or only a small defined population. Saha et al. quite rightly differentiate between traditional prevalence, or “core”, studies (these generate an estimate based on the population residing within a defined catchment area), and studies in specific sub-groups (which they divide into migrant studies and studies in other special groups). Using sequential filters they were able to isolate discrete data from multiple studies, and they used other strategies to ensure that the largest groups were counted. The authors had hypothesised that prevalence estimates would differ between lifetime, period, and point prevalence and that lifetime prevalence would be higher than lifetime estimates (estimates are calculated as a proportion by dividing the total number of individuals who manifest a disorder [the numerator] by the total population at risk including those with the disorder [the denominator]). They also predicted that the estimates would be higher for males, those from urban areas, and migrants. Case ascertainment methods and sample selection do influence prevalence rates, so Saha et al. chose studies that used comprehensive case ascertainment methods. Of the 132 core studies, 21 studies reported point prevalence, 34 reported period prevalence, and 24 reported lifetime prevalence. The median prevalence of schizophrenia was 4.6/1,000 for point prevalence, 3.3/1,000 for period prevalence, 4.0 for lifetime prevalence, and 7.2 for lifetime morbid risk. 

Point prevalence: The proportion of individuals who manifest a disorder at a given point in time. 

Period prevalence: The proportion of individuals who manifest a disorder over a specific period of time (e.g., over one year). 

Lifetime prevalence: The proportion of individuals in the population who have ever manifested a disorder, who are alive on a given day. 

Lifetime morbid risk: The probability of a person developing the disorder during a specified period of their life or up to a specified age (lifetime morbid risk differs from lifetime prevalence in that it attempts to include the entire lifetime of a birth cohort both past and future, and includes those deceased at the time of the survey). 

There were no significant differences between males and females, nor between urban, rural, and mixed sites, although migrants and homeless people had higher rates of schizophrenia and, not surprisingly, developing countries had lower prevalence rates (the lower prevalence of schizophrenia in developing countries has been previously documented). It is well known from other studies that migrants have higher than expected rates of schizophrenia, although definitions of migrants in these studies have been variable and the studies have suffered from a series of other methodological problems. 

Several important findings emerge from Saha and colleagues' analysis. For clinicians, the analysis indicates clearly that lifetime prevalence is 4.0/1,000 and not 1%, as reported in the Diagnostic and Statistic Manual of Mental Disorders, fourth edition, and other textbooks. The study also challenges the widely held view that schizophrenia is much more common in men. Saha et al.'s finding that schizophrenia was just as common in women has clear implications for developing services, since it means that not only must we develop and provide culturally appropriate services but also services that are gender sensitive (as the number of cases in women are higher than expected, gender becomes a more important factor). 

 Detailed economic measures must be included in analyses of the prevalence of schizophrenia to determine whether countries are developed or developing. Saha et al. themselves acknowledge that they have used a single measure of World Bank definitions relying on per capita income (whereas in any country there will be marked geographical variation in social and economic classes) for assessing a complex and multi-dimensional concept, which is a weak point of their systematic review. The impact of urbanization must be studied especially, as in many developing or low-income countries the migration into urban areas adds a tremendous amount of variation that must be taken into account in future ecological studies. 

Schizophrenia across Cultures: 

Studies have shown that the outcome of schizophrenia is better in developing countries, and therefore the point prevalence in these countries should be lower. Despite this clear difference in the course of schizophrenia in different cultures, cross-cultural research in psychiatry focuses on similarities rather than differences.

In the International Pilot Study of Schizophrenia and the Determinants of Outcome of Severe Mental Disorders study , catatonia (a form of schizophrenia characterized by a tendency to remain in a fixed stuporous state for long periods) was diagnosed in 10% of cases in developing countries compared with less than 1% in developed countries. Hebephrenia (a form of schizophrenia characterized by severe disintegration of personality) was present in 13% of cases in developed countries and 4% in developing countries. These differences in the disease in developed versus developing countries indicate that there is more to the prevalence of schizophrenia than simple epidemiological data. Better prognosis in developing countries may indicate different sets of etiological and perpetuating factors. 

 Cohen argued that although the case-finding method in both these studies was accurate, the vast majority of cases were identified in Western-type facilities, and therefore the numbers of true cases of schizophrenia may be an underestimate. He also pointed out that in developing countries the proportion of cases with acute onset schizophrenia was twice as high as in developed countries. Such variations may indicate a real difference in the cross-cultural manifestations of schizophrenia—hospital-based data collection reflects cultural processes that have little to do with the true prevalence and incidence rates of schizophrenia. 

While prevalence studies can help contribute to an understanding of the etiology of schizophrenia, psychodynamic issues—such as cultural identity and attachment—must also be studied, especially among migrant groups, as cultural congruity and ethnic density may influence the presentation of suffering individuals to psychiatric services. 

The Prevalance Rate for schizophrenia is approximately 1.1% of the population over the age of 18 (source: NIMH) or, in other words, at any one time as many as 51 million people worldwide suffer from schizophrenia, including;

•  6 to 12 million people in China (a rough estimate based on the population) 
•  4.3 to 8.7 million people in India (a rough estimate based on the population) 
• 2.2 million people in USA 285,000 people in Australia 
•  Over 280,000 people in Canada Over 250,000 diagnosed cases in britian. 

Global Schizophrenia Prevalence May Have Been Overstated:

Although previous studies have led to the common wisdom that schizophrenia affects 1 out of every 100 individuals, new data indicate that this prevalence may be too high. 

Schizophrenia may not be as prevalent as generally believed, according to a review of a whopping amount of data from 46 countries.

 The study that arrived at this conclusion was conducted by John McGrath, M.D., a professor of psychiatry at the University of Queensland in Australia, and coworkers. Results were published in the May Public Library of Science Medicine. 

 McGrath and his colleagues systematically reviewed the medical literature on schizophrenia prevalence—that is, the number of people experiencing the illness at a given time or within a time interval—in hopes of coming up with firm figures regarding such prevalence.

 This meant that they analyzed 188 studies conducted in 46 countries and published between 1965 and 2002. 

For those studies that reported on lifetime prevalence, the mean lifetime prevalence of schizophrenia (the proportion of individuals in the population who have ever manifested the illness and who are alive on a given day) was 4 per 1,000. DSM-IV-TR states that the lifetime prevalence of schizophrenia is often reported to be 5 to15 per 1,000. For those studies that reported on point prevalence of schizophrenia, the mean point prevalence was 4.6 per 1,000. Key policy documents have estimated the point prevalence of schizophrenia to be similar, about 4 per 1,000. 

 They likewise learned that the lifetime morbid risk of schizophrenia was 7 per 1,000. This estimate corresponds to findings from two other review studies. Moreover, it raises questions about the statement that people often make that "schizophrenia affects about one person in 100," McGrath and his coworkers pointed out in their report, because the statement is usually based on lifetime morbid risk figures. "If we wish to provide the general public with a measure of the likelihood that individuals will develop schizophrenia during their lifetime, then a more accurate statement would be that `about seven to eight individuals per 1,000 will be affected.

'" The researchers concluded, "While there is substantial variation between sites, generally the prevalence of schizophrenia ranges from 4 to 7 per 1,000 persons, depending on the type of prevalence estimate used." The review also suggests, in keeping with some previous studies, that schizophrenia is more prevalent in migrant groups than in native-born populations, adding weight to the argument that migrant status is an important risk factor for the illness. 

 Yet contrary to some previous findings, the review implies that schizophrenia is about as prevalent among women as among men and that it is not more widespread in urban areas than in rural ones. However, another recent study tends to bolster their gender-related findings: it found a greater prevalence of schizophrenia among females than among males in china.

Prevalence of depression

Prevalence of Depression:

Depression in Children and Adolescents:

A number of epidemiological studies have reported that up to 2.5 percent of children and up to 8.3 percent of adolescents in the U.S. suffer from depression. An NIMH-sponsored study of 9- to 17-year-olds estimates that the prevalence of any depression is more than 6 percent in a 6-month period, with 4.9 percent having major depression. In addition, research indicates that depression onset is occurring earlier in life today than in past decades. A recently published longitudinal prospective study found that early-onset depression often persists, recurs, and continues into adulthood, and indicates that depression in youth may also predict more severe illness in adult life. Depression in young people often co-occurs with other mental disorders, most commonly anxiety, disruptive behavior, or substance abuse disorders,  and with physical illnesses, such as diabetes.

       Prevalence of Depression by Race/Ethnicity:

Prevalence of major depressive disorder differed significantly by racial/ethnic group, with the highest prevalence in White participants. Mexican American and White individuals had significantly earlier onset of major depressive disorder compared with African American individuals .Overall, persons living in poverty had nearly 1.5 times the prevalence of major depressive disorder; however, poverty was significantly associated with prevalence of major depressive disorder only for White respondents. Lack of education (< 8 years of school) was significantly associated with prevalence of major depressive disorder only for Mexican American individuals^.

 In contrast to the comparative rates for major depressive disorder, the prevalence of dysthymic disorder was significantly greater among African American and Mexican American individuals compared with Whites. After we controlled for poverty, lack of education remained a significant risk factor for dysthymic disorder. In addition, significant interactions occurred between race/ethnicity, gender, and education in relation to prevalence of dysthymic disorder. Specifically, for White respondents (of both genders), a precipitous decline in prevalence of dysthymic disorder was seen with any education beyond middle school (> 8 years of education); however, for Mexican American and African American subjects, the incremental effect of education on the prevalence of dysthymia was less evident and depended on gender.

Prevalence statistics for Depression:

The following statistics relate to the prevalence of Depression:

·         6.5% of women have a major depressive disorder in the US (National Institute of    Mental Health, NIH)

·         3.3% of men have a major depressive disorder in the US (National Institute of Mental Health, NIH)

·         6.7 million women have a major depressive disorder in the US 1998 (National Institute of Mental Health, NIH)

·         3.2 million men have a major depressive disorder in the US 1998 (National Institute of Mental Health, NIH)

·         4-5% of population have major depression in Canada (National Population Health Survey, Health Canada).

Schizophrenia

Schizophrenia is a mental disorder characterized by a breakdown of thought processes and by poor emotional responsiveness.  It is a psychotic disorder characterized by loss of contact with the environment, by noticeable decline in the level of functioning in everyday life, and by collapsing of personality expressed as disorder of feeling, thought (as delusions), perception (as hallucinations), and behavior .

The disorder is thought mainly to affect cognition, but it also usually contributes to chronic problems with behavior and emotion. People with schizophrenia are likely to have additional conditions, including major depression and anxiety disorders; the lifetime occurrence of substance abuse is almost 50%. Social problems, such as long-term unemployment, poverty and homelessness, are common. The average life expectancy of people with the disorder is 12 to 15 years less than those without, the result of increased physical health problems and a higher suicide rate .

Symptoms:

First-rank symptoms by Kurt Schneider in schizophrenia

§  Audible thoughts (thought echo)

§  Voices heard arguing

§  Voices heard commenting on one's actions

§  Somatic/thought passivity experiences (delusions of control)

§  Thought withdrawal

§  Thought insertion - Thoughts are ascribed to other people who intrude their thoughts upon the patient

§  Thought broadcasting (also called thought diffusion)

§  Delusional perception (i.e. taking a normal sensory perception to mean a bizarre situation such as taking seeing an aeroplane as indicating the patient should be the next president).

Other symptoms includes :

·          Hallucinations (most reported are hearing voices), 

·         delusions (often bizarre or persecutory in nature), and 

·         disorganized thinking and speech.

·         Impairment in social cognition is associated with schizophrenia, as are symptoms of paranoia; social isolation commonly occurs.

·         Difficulties in working and long-term memory, attention, executive functioning, and speed of processing also commonly occur.

The latter may range from loss of train of thought, to sentences only loosely connected in meaning, to incoherence known as word salad in severe cases. Social withdrawal, sloppiness of dress and hygiene, and loss of motivation and judgment are all common in schizophrenia. There is often an observable pattern of emotional difficulty, for example lack of

responsiveness.  In one uncommon subtype, the person may be largely mute, remain motionless in bizarre postures, or exhibit purposeless agitation, all signs of catatonia.

Schizophrenia is often described in terms of positive and negative (or deficit) symptoms. Positive symptoms are those that most individuals do not normally experience but are present in people with schizophrenia.

Positive Symptoms:

They can include

·         delusions,

·         disordered thoughts and speech,

·         and tactile, auditory, visual, olfactory and gustatory hallucinations,Typically regarded as manifestations of psychosis.

Hallucinations are also typically related to the content of the delusional theme. Positive symptoms generally respond well to medication.

Negative symptoms

They are deficits of normal emotional responses or of other thought processes, and respond less well to medication.

·         They commonly include flat or blunted affect and emotion,

·         poverty of speech (alogia),

·         inability to experience pleasure (anhedonia),

·         lack of desire to form relationships (asociality),

·         and lack of motivation (avolition).

Research suggests that negative symptoms contribute more to poor quality of life, functional disability, and the burden on others than do positive symptoms. People with prominent negative symptoms often have a history of poor adjustment before the onset of illness, and response to medication is often limited.

Causes:

No single cause can account for schizophrenia. Rather, it appears to be the result of multiple causes such as genetic factors, environmental and psychological assaults, and possible hormonal changes that alter the brain's chemistry.

Abnormalities in Brain Structure, Circuitry, and Chemicals

Brain scans using magnetic resonance imaging (MRI) have shown a number of abnormalities in the brain's structure associated with schizophrenia. Such problems can cause nerve damage and disconnections in the pathways that carry brain chemicals.

Because these problems tend to show up on brain scans of people with chronic schizophrenia rather than newly diagnosed patients, some doctors believe they may be a result of the disease and its treatments rather than a cause. (Medications used for schizophrenia can also cause brain shrinkage over time.)

Abnormal Brain Chemicals. Schizophrenia is associated with an unusual imbalance of neurotransmitters (chemical messengers between nerve cells) and other brain chemicals, such as dopamine overactivity, glutamate, reelin, and others. Whether any changes in these chemicals in the brain is a cause or a consequence of schizophrenia remains unclear.

Abnormal Circuitry. Abnormalities in brain structure are also reflected in the disrupted connections between nerve cells that are observed in schizophrenia. Such miswiring could impair information processing and coordination of mental functions. For example, auditory hallucinations may be due to miswiring in the circuits that govern speech processing. Strong evidence suggests that schizophrenia involves decreased communication between the left and right sides of the brain.

Genetic Factors

Schizophrenia undoubtedly has a genetic component. The risk for inheriting schizophrenia is 10% in those who have one immediate family member with the disease and about 40% if the disease affects both parents or an identical twin. Family members of patients also appear to have higher risks for the specific symptoms (negative or positive) of the relative with schizophrenia.

Researchers are seeking the specific genetic factors that may be responsible for schizophrenia in such cases. Current evidence suggests that there are a multitude of genetic abnormalities involved in schizophrenia, possibly originating from one or two changes in genetic expression. Scientists are beginning to discover the ways in which specific genes affect particular brain functions and cause specific symptoms. Genes that have been studied include the neuregulin-1 gene, the OLIG2 gene, and the COMT gene.

Heredity does not explain all cases of the disease. About 60% of people with schizophrenia have no close relatives with the illness.

Infectious Factors

The case for viruses as a cause of schizophrenia rests mainly on circumstantial evidence, such as living in crowded conditions. The risk is higher for people who are born in cities than in the country. The longer one lives in the city, the higher the risk. The following are some studies suggesting an association:

• Winter and Spring Births. The risk for schizophrenia worldwide is 5 - 8% higher for those born during winter and spring, when colds and viruses are more prevalent.
• Large Families. The risk for schizophrenia is also greater in large families in which there are short intervals between siblings (2 or fewer years). Such observations suggest that exposure to infection early in infancy may help set the stage for later development of the disease.
• Pregnant Mother's Exposure to Viruses. The mother's exposure to viral infections such as rubella, measles, chicken pox, or others while the infant is in the womb has also been associated with a higher risk for schizophrenia in her child.
• Researchers are trying to identify specific viruses that may be responsible for some cases. Of particular interest is research finding evidence of a virus that belongs to the HERV-W retrovirus family in 30% of people with acute schizophrenia.

Some research has found an association between some cases of schizophrenia and toxoplasmosis, a parasite carried by cats and other domestic animals. Several studies suggest that patients with schizophrenia have an increased prevalence of antibodies to toxoplasmosis. Toxoplasmosis can lie dormant in the nervous system and migrate to the brain over many years.

Psychological Factors

Although parental influence is no longer believed to play a major role in the development of schizophrenia, it would be irresponsible to ignore outside pressures and influences that may exacerbate or trigger symptoms. The prefrontal lobes of the brain, the brain areas often thought to lead to this disease, are extremely responsive to environmental stress. Given the fact that schizophrenic symptoms naturally elicit negative responses from the patient's circle of family and acquaintances, negative feedback may intensify deficits in a vulnerable brain and perhaps even trigger and exacerbate existing symptoms.

Types of Schizophrenia:

The DSM-IV-TR contains five sub-classifications of schizophrenia, although the developers of DSM-5 are recommending they be dropped from the new classification.

§  Paranoid type: Delusions or auditory hallucinations are present, but thought disorder, disorganized behavior, or affective flattening are not. Delusions are persecutory and/or grandiose, but in addition to these, other themes such as jealousy, religiosity, or somatization may also be present. (DSM code 295.3/ICD code F20.0)

§  Disorganized type: Named hebephrenic schizophrenia in the ICD. Where thought disorder and flat affect are present together. (DSM code 295.1/ICD code F20.1)

§  Catatonic type: The subject may be almost immobile or exhibit agitated purposeless movement. Symptoms can include catatonic stupor and waxy flexibility. (DSM code 295.2/ICD code F20.2)

§  Undifferentiated type: Psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met. (DSM code 295.9/ICD code F20.3)

§  Residual type: Where positive symptoms are present at a low intensity only. (DSM code 295.6/ICD code F20.5)

§   

The ICD-10 defines two additional subtypes:

§  Post-schizophrenic depression: A depressive episode arising in the aftermath of a schizophrenic illness where some low-level schizophrenic symptoms may still be present. (ICD code F20.4)

§  Simple schizophrenia: Insidious and progressive development of prominent negative symptoms with no history of psychotic episodes. (ICD code F20.6).

Treatment:

Medication:

The first-line psychiatric treatment for schizophrenia is antipsychotic medication, which can reduce the positive symptoms of psychosis in about 7–14 days. Antipsychotics, however, fail to significantly ameliorate the negative symptoms and cognitive dysfunction. Long term use decreases the risk of relapse.

Therapy for Schizophrenia

Through therapy, people can develop social and work skills to improve their lives and relationships.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, cognitive behavioral therapy (CBT), token economic interventions, and psychosocial interventions for substance use and weight management. Family therapy or education, which addresses the whole family system of an individual, may reduce relapses and hospitalizations. The evidence for CBT's effectiveness in either reducing symptoms or preventing relapse is minimal.^[ Art or drama therapy have not been well-researched.

Electroconvulsive Therapy and Schizophrenia

ECT is often misunderstood, but it’s highly effective for certain types of schizophrenia.