3. Diagnosis & Classification
Monday, January 21, 2013 9:00 AM
What is diagnosis?
• What does it mean to "diagnose"?
○ A diagnosis is an identification of a condition or disease state
○ This is a medical notion that may or may not apply to psychological problems
○ Need a diagnostic system-- a collection of rules for guiding us in our determination of a diagnosis
• [In psychiatry, a diagnosis is solely descriptive]
A "cold" is different from pneumonia in that…
Depression is different from anxiety
What do we want in a diagnostic system?
• Need descriptors that allow different clinicians to recognize the same disorder (reliability)
• Need descriptors such that if present, they indicate the presence of a disorder, and if absent, the disorder is absent (validity)
• Yet, that is not so easy
○ How do you know if someone is depressed?
Is it enough for someone to say "I am depressed?"
Does the person have to cry a lot or talk of suicide?
[Not all depressed people present with the same symptoms, there isn't one symptom that is necessary or sufficient]
Is loss of appetite a symptom, or poor sleep?
○ To answer such questions, someone must first define what depression is
○ Hippocrates: beginnings of a diagnostic system
○ Kraeplin (19th century)
First comprehensive diagnostic system based on which characteristics occur together
• 1948: World Health Organization
○ Extended "International List of the Causes of Death" to include psychological abnormalities
○ The list was renamed the International Statistical Classification of Diseases, Injuries, and Causes of Death (ICD)
○ Current: ICD-10
• 1952-- American Psychiatric Association published its own diagnostic system, the Diagnostic and Statistical Manual of Mental Disorders (DSM)
○ Diagnostic categories were:
Heavily psychoanalytic-- manuals focused on unobservable internal states
Not based in empirical research
Did not involve objective criteria
○ Consequently, it was not very useful, and different clinicians would come up with different diagnoses for the same person
• 1968: DSM-II
○ Suffered from many of the same problems as the original DSM
• 1980: DSM-III
○ Radically different from DSM-II
Multi-axial classification-- rather than using a single label, client described in terms of a number of clinically important factors, or axes
Focus on descriptive features that allow identification of the problem rather than interpretation based on unvalidated theories
Provided detailed criterion sets for each disorder, to allow various clinicians to diagnose in a similar way
Attempted to be atheoretical; eliminated theory-laden terms such as "neurosis" (psychoanalytic)
• 1987: DSM-III-R-- a minor revision
• 1994: DSM-IV-- major revision, still using the multiaxial approach
○ Development team searched for an empirical basis for each disorder, and carried out extensive field trials using the classification system
Evaluated more than 6000 subjects, using hundreds of clinicians, looking at reliability and validity
○ Developers took more international approach; Cooperated with the developers of ICD-10 which is widely used around the world outside of North America
• 2000: DSM-IV-TR-- relatively minor changes to text
○ Translated into French as well
• For both the DSM and ICD (which will be discussed later), diagnoses are defined purely in terms of symptoms
○ Quite different from diagnosis in physical medicine
○ In physical medicine, data not available from the patient is gathered by tests-- blood tests, x-rays, etc.
○ Medical diagnoses adds new information about the disorder-- causation, course, treatment, etc.
○ [Psychological tests are descriptive and do not add new information, this is a huge misconception in psychology]
• Yet, DSM provides some consistency so that when terms such as depression or anxiety are used, people are describing more or less the same problems
• In DSM-IV, each mental disorder is conceptualized as:
○ "A clinically significant behavioral or psychological syndrome or pattern that occurs in an individual and that is associated with present distress (e.g., a painful symptom) or
disability (e.g., impairment in one or more important areas of functioning) or with a significantly increased risk of suffering death, pain, disability or an important loss of
freedom." (DSM-IV p. xxi)
Excluding simple deviance from societal norms
Excluding expected or culturally sanctioned responses-- as to the death of a loved one
• In DSM-IV, NOT assumed that all categories are mutually exclusive, that there is no overlap
○ Because of the continuum between normal and abnormal functioning, often only need to fill a subset of conditions to warrant the diagnosis
○ Aim is to describe accurately the various disorders rather than interpret them
Major Axes in DSM-IV