Construct validity This type of validity involves testing hypotheses based on the diagnosis of schizophrenia. RESEARCH EVIDENCE The dopamine hypothesis suggests that schizophrenia is linked to high levels of dopamine and so if individuals with schizophrenia have high levels of dopamine then this provide some evidence for construct validity. EVALUTION This type of validity raises issues when it is not supported. This is because it is not clear if this is because the diagnosis is wrong or the hypothesis is wrong. The genetic hypothesis offers support. The genetic hypothesis (that schizophrenia has a genetic basis) has reasonable construct validity because it is supported by numerous twin and family studies and genetic factors are probably more important in the development of schizophrenia than almost any other mental disorder. Predictive validity This refers to our ability to predict the eventual outcome for patients who receive a diagnosis of schizophrenia. RESEARCH EVIDENCE The predictive validity of a diagnosis of schizophrenia is reasonable, but not good because there is too much variety in the outcomes of schizophrenia. For example, 20% recover and never have another episode whereas 10% of schizophrenics commit suicide (Birchwood & Jackson, 2001, see A2 Level Psychology page 384). EVALUATION Predictive validity is lowered by the fact there are so many diverse symptoms of schizophrenia that patients’ experiences of the disorder are very different. Mason et al. (1997, see A2 Level Psychology page 385) found predictive validity was higher when a 6-month period of symptoms was used as the basis for diagnosis because this cuts out individuals who have a brief, psychotic disturbance. Social class bias and culture bias Two possible biases, social class bias and culture bias, could reduce reliability and validity.
Construct validity This type of validity involves testing hypotheses based on the diagnosis of schizophrenia. RESEARCH EVIDENCE The dopamine hypothesis suggests that schizophrenia is linked to high levels of dopamine and so if individuals with schizophrenia have high levels of dopamine then this provide some evidence for construct validity. EVALUTION This type of validity raises issues when it is not supported. This is because it is not clear if this is because the diagnosis is wrong or the hypothesis is wrong. The genetic hypothesis offers support. The genetic hypothesis (that schizophrenia has a genetic basis) has reasonable construct validity because it is supported by numerous twin and family studies and genetic factors are probably more important in the development of schizophrenia than almost any other mental disorder. Predictive validity This refers to our ability to predict the eventual outcome for patients who receive a diagnosis of schizophrenia. RESEARCH EVIDENCE The predictive validity of a diagnosis of schizophrenia is reasonable, but not good because there is too much variety in the outcomes of schizophrenia. For example, 20% recover and never have another episode whereas 10% of schizophrenics commit suicide (Birchwood & Jackson, 2001, see A2 Level Psychology page 384). EVALUATION Predictive validity is lowered by the fact there are so many diverse symptoms of schizophrenia that patients’ experiences of the disorder are very different. Mason et al. (1997, see A2 Level Psychology page 385) found predictive validity was higher when a 6-month period of symptoms was used as the basis for diagnosis because this cuts out individuals who have a brief, psychotic disturbance. Social class bias and culture bias Two possible biases, social class bias and culture bias, could reduce reliability and validity.
Revision_Guide_-_Clinical_Characteristics_and_Diagnosis_of_Schizophrenia.docx