Reliability + Validity

• Gender Bias


  Judgements on stereotypical beliefs held about gender
• Longenecker found that since the 1980's men have been diagnosed with schizophrenia more often than women
• Loring and Powell found that when patients were described as 'males' or given no gender, 56% of psychiatrists diagnosed schizophrenia. But when they were 'female' only 20% were diagnosed with schizophrenia
• Schizophrenia is not being diagnosed correctly for all patients so there is low validity and as there is difference between psychiatrists, there is low reliability in the diagnosis of schizophrenia
• Culture Bias


  The DSM and ICD are based on western cultures views of what is healthy and unhealthy, but this could distort or bias your judgment when used to diagnose behaviors in other cultures
• African American and English people of Afro-Caribbean origin are several times more likely than white people to be diagnosed with schizophrenia. Yet rates in Africa and West-Indies are not particularly high so it cannot be that they have a genetic vulnerability
• There is a bias in how Western psychiatrists are defining and diagnosing Schizophrenia
• Positive symptoms such as hearing voices may be more acceptable in African cultures because of cultural beliefs in communication with ancestors, and so people are more ready to acknowledge such experiences
• To them, hearing voices may be seen as a positive thing and something to be proud of
• Social norms affects the diagnosis of schizophrenia
• Co-Morbidity


  Where two conditions co-exist in the same individual at the same time
• A person with schizophrenia might also at the same time be suffering from another condition, e.g. personality disorder, depression, alcoholism, etc.
• If conditions occur together a lot of the time, then this calls into question the validity of their diagnosis and classification
• If half of patients with schizophrenia are diagnosed with depression, then psychiatrists may be poor at telling the disorders apart
• If very severe depression looks a lot like schizophrenia, they may be better as a single condition
• A meta-analysis by Swets found that at least 12% of patients with Schizophrenia also fulfilled the criteria for OCD and about 25% displayed significant OCD symptoms
• Buckley found that around 50% of patients with Schizophrenia have depression, 47% have substance abuse, 29% have PTSD whilst 23% have OCD
• Symptom Overlap


  When two or more conditions share the same symptoms
• Where conditions share many symptoms, it calls into question the validity of classifying the two disorders separately; so whether Schizophrenia is a separate disorder to those it shares its symptoms with
• Shared symptoms could lead to an unreliable or incorrect diagnosis (not valid) because the person may exhibit a symptom typical of schizophrenia (e.g. delusions) but could instead have another condition with the same symptom (e.g. bipolar disorder)
• Schizophrenia and bipolar both have symptoms of delusions, hallucinations and lack of motivation
• Serper assessed patients with co-morbid schizophrenia and cocaine abuse, cocaine intoxication on its own and schizophrenia on its own. Despite having symptom overlap in patients with schizophrenia and cocaine abuse, it was actually possible to make accurate diagnoses, showing that symptom overlap did not affect the validity of a diagnosis and clinicians can tell the difference between the illnesses