Classification & Research. The study of mental disorder involves: Definition: What do we mean by mental disorder? Classification: How do we distinguish.
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Classification & Research
The study of mental disorder involves:
Definition: What do we mean by mental disorder?
Classification: How do we distinguish between different mental disorders?
Explanation: How do we understand mental disorder?
Treatment: How do we treat mental disorder?
Example
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• LINNAEAN CLASSIFICATION
• Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Mammalia Subclass: Theria Infraclass: Eutheria Order: Primates Suborder: Anthropoidea Superfamily: Hominoidea Family: Hominidae Genus: Homo Species: sapiens
Why is it important to classify mental disorders?
Scientific communication and research
Treatment
Classification and Diagnosis
Classification systems exists before and independently any individual
Individual people are said to be diagnosed or put into the classification system based on a psychological assessment
Evaluating classification systems and assessment tools?
Reliability: Gives the same answer with repeated measurement or assessmentTest re-testInter-rater or inter-judge
Evaluating classification systems and assessment tools?
Validity: Measures or assesses what it claims to measureDescriptive, constructPredictive
Three broad ways to classify mental disorder
Categorical Approach Dimensional Approach Prototypal Approach
Categorical Approach
Characteristic of medical diagnostic systems.
Assumptions:Behavior can be divided into categories
of “healthy” and “disordered”.There are discreet, non-overlapping
types of “disorder”Members of each diagnostic group share
the same features.
Dimensional Approach
Characteristic of personality assessment approaches.
Assumptions:Behavior comes from different
strengths/intensities of underlying attributes (e.g., aggressiveness, introversion).
People differ along a continuum of normality to abnormality on these dimensions.
Prototypal Approach There are imperfect but recognizable
combinations of characteristics that cluster together.
These imperfect clusters define abnormal behavior.
Assumptions:No people share all of the features of the
prototype.All people share most of the features of
the prototype.
Defines what is abnormal Classifies mental disorders into different sub-
types and provides defining criteria
Medical tradition: Categorical in intention Prototypal in practice
DSM-IV
Created with assumptions of the categorical approach
BUT…Central features of Dx categories are
sometimes unclear.Many shared features between Dx
categories.Large amount of co-morbidity.
DSM-IV
DSM-IV classification is prototypal because...Fuzzy boundaries between
categories.Overlap of categories themselves.
DSM-IV: A short history
DSM = Diagnostic and Statistical Manual (of mental disorders)
Currently in 4th edition (May, 1994).
DSM I and II: Included a lot of jargon. Narrative categories. Categories not well defined. Generally not reliable.
DSM III (1980): Radically new approach...
DSM-III
Precise definitions of Dx categories. Necessary requirements to meet Dx
category. First attempts to establish reliability
and validity for Dx categories.
DSM-IV
Latest edition (1994) Five Axis structure:Axis I - Clinical SyndromesAxis II - Personality DisordersAxis III - Related Medical ConditionsAxis IV - Psychosocial and Environmental
ProblemsAxis V - Global Assessment of
Functioning.
DSM-IV criticisms:
1. Long-term outcome of disorders is largely unknown.
2. Still little known about etiology.3. High co-morbidity among Dx.4. Reliability emphasized at expense of
validity (?)
DSM-IV criticisms cont.
5. Perpetuation of flawed Dx categories (from past DSMs).
6. Too many dimensions require rating.
Classification
Problems
Labeling
Pseudo-explanations
Lack of reliability
Classification
Advantages:
Communication shorthand Treatment planning Etiology Aid to scientific investigation
Further Exploration: Classification Millon, T. (1991). Classification in
Psychopathology: Rationale, Alternatives, and Standards. Journal of Abnormal Psychology, 100(3), 245-261.
Krueger, R., Piasecki, T., M. (2002). Toward a dimensional and psychometrically-informed approach to conceptualizing psychopathology. Behaviour Research and Therapy, 40, 485-499.
Research Methods and Critical Thinking
Observation
Like all sciences the “bedrock” is observation/descriptionObservation as theory free or theory
ladenDescription determines what we can
then later say about a phenomenonReliability and Validity
Hypotheses & Predictions
Hypothesis: A claim about observations/descriptions that could be true or false that attempts to explain or understand the worldTested by making predictions
Prediction: also important from a clinical point of view, not just to test hypothesesCan predict without understanding
Understanding
Understanding: Usually means “what causes X” could also mean “what is it like, or what does it mean to a person to have X”
Causality:
Requirements for inferring causality:1) Covariation - purported cause and
observed effect vary together.2) Temporal Precedence - purported
cause occurs before the observed effect.
3) Exclusivity - the purported cause is the only thing that can explain the observed effect.
Correlation / Covariation vs. Causation
Hypothesis: Stress causes depressionNeed to show that depressed people
(Criterion Group) had higher stress levels, before becoming depressed, than other people who do not become depressed (Control Group).
Control / Intervention
Without understanding it is hard to control or intervene
Research Designs
Intensive observation of a single case Observation of groups
Internal and External Validity
Internal validityThe study can make accurate
conclusions because there are no confounds or alternative explanations
External validityThe results can be generalized to
people outside the study
Sampling and Generalization
Population: Everyone who has the mental disorder that you want to make claims about
Sample: A smaller group of people from the lager population of interest
Random Sampling: Everyone in the population has an equal chance of being in the sample
Sampling and Generalization
If the sample is not random, or not a good mix of all the people that have the mental disorder then the conclusions may not have external validity or may not generalize
Methods of Control
Manipulating or systematically changing one variable while controlling or holding constant other variables
Allows us to conclude that any observed effects of changing a variable are really due to it and not other variable
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