Issues in diagnosis +classification

• One strength of diagnosis of SZ is its reliability
• What does reliability mean?

  Consistency
• Osorio et al. found excellent reliability for SZ diagnosis in 180 individuals using DSM 5. Inter-rater reliability: 97 % Test-retest reliability: 92 %
• One limitation of diagnosis of SZ is low validity
• Cheniaux et al. had 2 psychiatrists independently assess the same 100 clients using ICD 10 and DSM 5 criteria. Found that 68 were diagnosed with SZ under ICD 10 and 39 under DSM 5. Suggests SZ is either over or under diagnosed according to diagnostic system
• What is co-morbidity?

  When conditions occur together at the same time. Calls into question validity of diagnosis and classification as they might be one single condition
• Buckley et al. found that among individuals with Sz:

  • 50 % also had depression
  • 47 % substance abuse
  • 23 % OCD
• Co morbidity raises a problem for classification because it means SZ may not exits as a distinct condition and raises a problem for diagnosis as some people with SZ may have unusual cases of conditions like depression
• Gender bias

  Since 1980s men have been diagnosed with SZ more commonly that women ( ratio of 1.4 : 1)
• What is one possible explanation for men being more often diagnosed?

  Women are less vulnerable than men perhaps due to genetic factors
• Alternative explanation to gender difference in diagnosis?

  Cotton et al. suggest that women are under diagnosed because they have closer relationships and henc get support. This leads to women with SZ often functioning better than men
• Culture bias

  Some symtoms of SZ, particularly hearing voices, have different meaning in different cultures. E.g. in Haiti, some believe that voices are communications from ancestors
• British people of African Caribbean origin are up to 9 times more likely to be diagnosed than white Brits
• Symptom overlap

  E.g. SZ and bipolar disorder involve positive symptoms like delusions and negative symptoms like avolition. In terms of classification, this suggest that the two may not be two different conditions but variations of a single condition. In terms of diagnosis, it means SZ is hard to distinguish from bipolar disorder