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Research Methods for Studying Mental Disorders

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• Scientific method– Systematic data collection, controlled

observation, and testing hypotheses

• Hypothesis – Tentative explanation for certain facts or

observations

• Theory – Group of principles and hypotheses that

together explain some aspect of a particular area of inquiry

Research Methods Used to Study Mental Disorders

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• Replication– Repeating results under similar test conditions

• Replicating research has resulted in changes to previous “conclusive” results– Examples:

• Childhood vaccines may cause autism

• Antidepressants raise suicide risk in children and adolescents

• Most sexually abused children exhibit signs of trauma

Importance of Replication

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• Development of hypotheses about relationships

• Potential for self-correction

• Consideration for reliability and validity

• Use of operational definitions

• Acknowledgement of base rates

• Evaluation based on statistical significance

Characteristics of Clinical Research

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• Best tool for testing cause-and-effect relationships

• Components of a simple experiment– Experimental hypothesis

– Independent variable• Manipulated by the experimenter

– Dependent variable• Expected to change as a result of manipulating the

independent variable

Experiments

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• Experimental group– Group exposed to an independent variable

• Control group– Similar in every way to experimental group

but not exposed to independent variable

• Placebo group– Participants receive an inactive substance

• Over 75 percent of participants may correctly guess their position in this group based on effects

Types of Groups in an Experiment

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• Design of the experiment– Single-blind design

• Participants unaware of purpose of research

– Double-blind design• Participant and individual working directly with the

participant unaware of the experimental conditions

• Some variables cannot be manipulated– Example: child abuse

– Correlational studies are appropriate

Additional Controls in Experimental Research

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• Statistical analysis to determine correlation between variables

• Allow analysis of variables that cannot or should not be controlled

• Types of correlation– Positive correlation

– Negative correlation

– No correlation

Correlational Studies

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Possible Correlations Between Two Variables

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• Investigation that attempts to simulate real-life situation under controlled conditions

• Used when not possible to control all variables in real-life situations – Or when ethical, legal, or moral issues

preclude other types of studies

Analogue Studies

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• Behaviors and events are observed and recorded in their natural environment

• The main technique is observation– Sometimes with interviews or questionnaires

• Observers must be highly trained– Avoid disrupting the natural environment

• Provides no information about causality

• Difficult to control variables

Field Studies

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• Most studies are nomothetic– Study large numbers of people collectively

• Idiographic study– In-depth study of one person

– Used to examine a rare or unusual phenomenon

• Types of single-participant studies– Case study

– Single-participant experiment

Single-Participant Studies

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• Intensive study of one individual– Relies on clinical data

• Observations

• Medical and psychological tests

• Historical and bibliographic information

• Can determine characteristics, course, and outcome of a rare disorder

• Used to study therapeutic or diagnostic techniques

Case Study

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• Some aspect of a person’s behavior is used as a control (baseline) for comparison with future behaviors

• Multiple-baseline study – Baselines on two or more behaviors or the

same behavior in two or more settings are obtained prior to intervention

• Raises questions about external validity

Single-Participant Experiment

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A Multiple-Baseline Study

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• Methods for studying biological processes involved in mental illness– Endophenotypes

– Twin comparisons

– Genetic studies

– Study of the epigenetic processes

Biological Research Strategies

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• Endophenotypes: measurable characteristics– Characteristic must be heritable

– Occur more frequently in affected families than in the general population

– Examples: anatomical or chemical differences in the brain, eye-tracking irregularities

• Guide prevention and early treatment efforts

The Endophenotype Concept

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• Monozygotic (identical) twins– Share the same DNA

– Have different fingerprints

– Develop more differences from one another as they age

• Fraternal twins– Share same childhood environments

– Often used to evaluate hereditary versus environmental influences on development

Twin Studies

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• Goal: determine whether a disorder follows a genetic pattern

• If disorder is genetically linked:– Individuals closely related to person with

disorder (proband) more likely to display disorder

• Penetrance– Proportion of individuals with a particular

genotype who manifest the phenotype

Genetic Linkage Studies

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• Study of environmental factors that influence whether or not a gene is expressed

• Builds on idea that certain environmental factors have greatest impact during sensitive periods in development

• Epigenetic changes can leave an imprint on eggs or sperm– Affects traits inherited by future generations

Epigenetic Research

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• The use of animal models is a frequent practice– Allows for better control of variables

– Permits experimental procedures not practical to use on humans

– Example: newborn mice separated from mothers resulted in different behavior, emotional development, and gene expression

• Researchers were able to pinpoint the occurrence of exact biological processes

Using Animals in Biological Research

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• Examines rate and distribution of mental disorders in the population

• Prevalence– Percentage of individuals in targeted

population with a particular disorder during a specific period of time

• Incidence– Number of new cases of a disorder that

appear in an identified population within a specific period of time

Epidemiological Research

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• Meta-analysis: simplified process of comparing numerous research findings– Published versus unpublished studies

• Increasing emphasis on evidence-based practice

• Concerted effort to reduce bias and misconduct

• Focus on locating biomarkers and endophenotypes for particular disorders

Contemporary Trends and Future Directions

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• What methods do researchers use to study the causes of and treatments for psychopathology?

• How does biological research help us understand causes of abnormal behavior?

• Why is epidemiological research important in understanding mental illness?

• What are current trends in psychopathology research?

Review