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