Schizophrenia

• What is schizophrenia?

  A mental disorder characterized by abnormal social behavior and a distorted perception of reality. Schizophrenia is a long-term mental health condition that causes a range of different psychological symptoms.
• Schizophrenia is a type of psychosis which?

  • a severe mental disorder in which thoughts and emotions are so impaired that contact is lost with external reality
• What is a positive symptom?


  something extra e.g. a behaviour or biological reaction that was not present before.
• What is a negative symptom?

  a reduction or loss of normal function.
• ICD is the International Statistical Classification of Diseases and Related Health Problems. Who was it published by?


  World Health Organization (WHO) It contains codes for diseases, signs and symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or diseases.
• DSM is the Diagnostic and Statistical Manual of Mental Disorders. Who was it published by?


  • It is the classification and diagnostic tool published by the American Psychiatric Association (APA). ​
  • In the United States, the DSM serves as the principal authority for psychiatric diagnoses. 
• Schizophrenia can usually be diagnosed if a patient has experienced one or more of the following symptoms most of the time for a month: 

  • delusions​
  • hallucinations​
  • hearing voices​
  • incoherent speech​
  • negative symptoms, such as a flattening of emotions, avolition and speech poverty
• • ICD-10 defines 7 sub-types of schizophrenia.​
  • DSM-5 no longer defines sub-types.​
  • Subtypes had been defined by the predominant symptom at the time of diagnosis. ​
  • However, these were not helpful to doctors because patients’ symptoms often changed from one subtype to another and presented overlapping subtype symptoms, which blurred distinctions among the five subtypes and decreased their validity. 
• What are delusions?


  Delusions are a belief in something that is not (and often could not be) true.
• What are hallucinations?

  Hallucinations involve experiencing stimuli that are not present.
• What are some positive symptoms?

  • Hallucinations – unusual sensory experiences.​
  • Delusions - irrational beliefs.
• What are some negative symptoms?

  • Speech poverty – a reduction in the amount and quality of speech.​
  • Note – speech disorganisation (incoherent speech) is classed as a positive symptom in DSM.​
  • Avolition - difficulty beginning or continuing goal-directed activity.​
• What is incidence?


  Incidence refers to the proportion of new cases per unit of time (usually one year)
• What is prevalence?

  Prevalence refers to the proportion of existing cases (both old and new). 
• Three types of prevalence rate can be used:

  • point prevalence: a measure of the number of cases at a specific point in time​
  • period prevalence: the number of cases over a defined period (usually six months or one year)​
  • lifetime prevalence: the proportion of individuals who have been affected by a disorder at any time during their lives
• Warner and de Girolamo, 1995


  Considering differences in diagnostic assessment, case-finding methods and definition of adulthood, we can say that the incidence of schizophrenia is remarkably similar in different geographical areas
• Who said this? High incidence figures have recently been reported in some disadvantaged social groups and ethnic minorities in western Europe


  King et al., 1994; Selten and Sijben, 1994
• RELIABILITY IN DIAGNOSIS AND CLASSIFICATION

  • Diagnostic reliability means that a diagnosis of schizophrenia must be repeatable.​
  • Clinicians must be able to reach the same conclusions at 2 different points in time (test-retest reliability) or different clinicians must reach the same conclusions (inter-rater reliability).
• Recent studies have shown inter-rater reliabilities as high as 98% (Jakobsen et al, 2005).​

  However, Read et al (2004) found only a 38% concordance rate in test-retest reliability.
• What are the threats to validity?

  • Culture bias​
  • Gender bias​
  • Co-morbidity​
  • Symptom overlap
• Luhrman et al (2015) researched the influence of cultural environment on the main characteristic of schizophrenia, 'hearing voices'
• Luhrman 60 adults diagnosed with schizophrenia were interviewed, 20 each in Ghana, India, and the US
• Gender bias in the diagnosis of schizophrenia is said to occur when accuracy of diagnosis is dependent on the gender of an individual. ​


  The accuracy of diagnostic judgements can vary for a number of reasons, including gender biased diagnostic criteria or clinicians basing their judgements on stereotypical beliefs held about gender. 
• Gender bias validity

  Men are more commonly diagnosed with Sz than women.

  • Males are more likely to be involuntarily committed to psychiatric institutions when they show mild signs of Sz.​
  • Much of the early research into Sz was carried out on men.
• Gender bias validity

  • The usual age of onset form men is earlier than for women.​
  • Women with schizophrenia tend to have better functioning before the development of their Sz and a better course of the illness.​
• what is symptom overlap?


  Many of these symptoms of Sz are also found in other disorders, such as depression and bipolar disorder.
• what is comorbidity?

  • Two or more conditions can occur in the same patient at the same time. ​
  • Psychiatric co-morbidities are common among patients with schizophrenia. ​
  • These include substance abuse, anxiety and symptoms of depression.
• The possible genetic origin of Sz has been explored using 3 methodologies:

  • Twin studies​
  • Look for concordance rate​
  • Adoption studies​
  • Still look at twins but in situations where one has been adopted into a different family​
  • Family studies​
  • Incidence rates are compared among family members​
• Twin Studies​

  • Higher concordance rates for Sz between MZ twins than DZ twins strongly suggests a genetic causation.  ​
  • However, concordance rates are not 100%, which we would expect if the causation was completely genetic.​
  • These findings have been replicated many times elsewhere e.g. Davis et al (1995); Torrey (1992).​
• Twin studies evaluation

  • Higher concordance between MZ twins could be explained by greater environmental similarity rather than genetic similarity.​
• Gottesman and Shields (1982) study of MZ twins raised apart, challenges this point.​

  • It could also be argued that both of Gottesman and Shields’ studies lack population validity. ​
  • Samples are small in number, and twins are not representative of the wider population.  ​
  • This suggests that there are issues with the findings being generalised to the whole population. ​
• What do adoption studies do?

  • Adoption studies help to separate out the effects of environmental and genetic factors.  ​
  • Higher concordance rates between biological parents and their adopted children indicates a strong genetic link. ​
• Kety et al (1968)​ - adoption studies

  • To find out if there is a genetic basis for schizophrenia. ​
  • Researchers compared the adoptive family and the biological family of a schizophrenia-sufferer (the index participant) to see if there is a higher rate of schizophrenia-related illness among biological relatives than adoptive relatives.​
  • From the Psychiatric Register and other files, the names were obtained of adoptees who had been admitted to a psychiatric facility; 33 such cases were found. ​
• Kety et al (1968)

  Of 150 biological relatives of index cases 8.7% had a diagnosis of schizophrenia (or related condition); 1.9% with such diagnoses were found among the biological relatives of the controls.
• Tienari et al (1994)​

  • Finnish sample of schizophrenics' children given up for adoption was compared blindly with matched controls, who were adopted offspring of non-schizophrenic biological parents. ​
  • The adoptive families were investigated thoroughly using joint and individual interviews and psychological tests. ​
  • The biological parents were also interviewed and tested. ​
  • Among the 155 index offspring, the percentage of both psychoses and other severe diagnoses was significantly higher than in the 186 matched control adoptees. ​
•  Adoption studies - critics of kety et als

  • environment can lead to schizophrenia too: child abuse, neglect, bullying, drug and alcohol problems, all play a part. This can happen in an adoptive home too. ​
  • Tienari found that notable differences only emerged in the families which were rated as disturbed. ​
  • The genetic effect was only shown as a psychiatric disorder in the presence of a disturbed family environment. ​
  • The impact of disturbed family relations was strongest in the presence of the appropriate genotype.​
• Gottesman (1991) hows that the greater genetic similarity between family members, the greater the shared risk of schizophrenia.  ​What does this imply?

  • This strongly implies that there is a genetic factor in the cause of schizophrenia.​
  • However, it is also true that the closer the genetic similarity between family members, the greater the similarity in environmental factors: upbringing, life experiences etc.  ​
  • So nurture, rather than nature, could explain the findings.  ​
• schizophrenia is ...

  Polygenic.

  • The most likely genes are those coding for neurotransmitters, especially dopamine.​
  • Different studies have identified different candidate genes. ​
  • This suggests Sz is aetiologically heterogenous.​
• Some psychologists believe that schizophrenia is genetic. what is some evidence?

  Evidence to support this is Gottesman (1991), Kety et al (1968) and Tienari (1994).  These studies also support that the environment is important in schizophrenia, so the genetic theory is only half right.  
• • Family history and twin studies suggest that genes influence schizophrenia.  Gottesman found a correlation between genetic relatedness with a schizophrenia patient and the chance someone would have it.  DZ concordance was 17% and MZ was 48%, supporting a genetic influence but because the MZ concordance was not 100% the environment must also play a role.  


  a problem with these studies is that closely related people also live in similar environments so it might be due to environment