diagnosis & classification

• 2 diagnostic systems

  1. ICD-11
  2. DSM-5
• 🔹 ICD-11

  world health organisation

  • requires 2 or more characteristic symptoms e.g. delusions, hallucinations or disorganised speech
  • flexible on subtype classification
  • symptoms persist for 1 month or more
• 🔹 DSM-5

  american psychiatric association

  • requires 1 positive symptom e.g. delusions, hallucinations or disorganised speech
  • symptoms persist for 6 months with 1 active month
  • removes subtypes
• ➕ positive symptoms

  excess of normal functions

  1. hallucinations
  2. delusions
  3. disorganised speech
• 👻 hallucinations

  • sensory experiences with no external stimulus
  • involve any senses (auditory is most common)
  • voices may be critical, commanding or commenting
• 💭 delusions

  • strongly held false beliefs resistant to reason or evidence
• 😶 disorganised speech

  • loose associations, tangentiality or incoherence
  • catatonic behaviour
• ➖ negative symptoms

  loss of normal function

  1. avolition
  2. speech poverty
  3. flat affect
• 🐢 avolition

  • decrease in motivation
  • inability to maintain goal-directed behaviour
  • poor hygiene, little interest in social activities or apathy
• 🗣️ speech poverty

  • reduction in speech fluency and productivity
  • limited output of thought
• 📄 flat affect

  lack of emotional expression, monotone voice or unchanging facial expression
• 🔁 inter-rater reliability

  degree to which different clinicians agree on a diagnosis

  • Cheniaux et al - diagnosed 100 patients (ICD = 68 and DSM = 39)
  • inconsistency shows low reliability
• 🔁 test-retest reliability

  consistency of diagnosis over time

  • patients can receive different diagnoses at different times
• 👥 co-morbidity

  presence of 1 or more additional disorders

  • high rates with depression, anxiety or substance abuse
  • complicates diagnosis and treatment
• 🤞🏼 symptom overlap

  many symptoms also appear in other disorders

  • hallucinations and delusions occur in bipolar disorder
  • leads to misdiagnosis
  • reduces construct validity
• 🙏 culture bias

  • african-caribbean individuals are more likely to be diagnosed
  • misinterpretation of culturally specific behaviour
  • diagnostic tools may be culturally biased
• 🧍🏼‍♂️🧍🏼‍♀️gender bias

  • underdiagnosed in women due to better masking
  • clinicians have preconceived notions
• ❌ limitation of reliability - inter-rater

  low inter-rater reliability

  • Cheniaux et al - one psychiatrist diagnosed 70 patients and other diagnosed 37
  • inconsistency undermines reliability
  • people could be wrongly diagnosed or miss treatment
• ❌ limitation of reliability - test-retest

  lacks consistency over time

  • patient meets the criteria at one time but not at another
  • symptoms are subjective and vary in intensity and interpretation
  • reduces overall credibility
• ✅ strength of reliability - improvements

  modern diagnostic tools

  • DSM-5 - requires 1 positive symptom reducing subjectivity
  • positive symptoms are easier to identify consistently
  • makes diagnosis more standardised
• ❌ limitation of validity - symptoms

  overlap of symptoms

  • bipolar and schizophrenia both involve delusions and hallucinations
  • difficult to distinguish which leads to misdiagnosis
  • challenges discriminant validity
• ❌ limitation of validity - co-morbidity

  high comorbidity with other conditions

  • Buckley et al - 50% of patients also have depression and 47% have substance abuse
  • unclear as to whether schizophrenia is a distinct disorder
  • poor construct validity
• ❌ limitation of validity - bias

  cultural biases

  • afro-caribbean individuals are more likely to be diagnosed
  • clinicians misinterpret culturally specific behaviours as symptoms
  • low external validity