Research Methods

Basic Components of Research

  • Three main topics for research on psychopathology:

    • The nature of the problems people report

    • The causes, or etiology, of psychopathology

    • Treatment evaluation

  • Starts with a hypothesis or educated guess

    • Hypotheses in science are formulated so that they are testable

  • Research design

    • A method to test hypotheses about the independent and dependent variables

Considerations in Research Design

  • Internal validity vs. external validity

    • Interval validity: The extent to which results of a study are due to the independent variable

    • External validity: The extent to which results of a study are generalizable to the population it is studying

  • Ways to increase internal validity by minimizing confounds

    • Use of control groups

    • Use of randomization procedures

    • Use of analogue models

Statistical Versus Clinical Significance

  • Statistical methods help to protect against biases in evaluating data

  • Statistical vs. clinical significance

    • Statistical significance: Are the results due to chance?

    • Clinical significance: Are results clinically meaningful and likely to make a real difference in people’s lives?

  • Balancing statistical versus clinical significance

    • Evaluate effect size and social validity

  • Patient uniformity myth

    • Researchers sometimes mistakenly see all participants as one homogenous group

Studying Individual Cases

  • Case study method

    • Extensive observation and detailed description of a single client

    • Foundation of early historic developments in psychopathology

  • Limitations

    • Lacks rigor and

    • Internal validity is typically

    • Often entails numerous confounds

Correlational Research

  • Assess the degree to which levels of certain variables are linked to levels of other variables

  • The nature of correlation

    • Statistical relation between two or more variables

    • No independent variable is manipulated

    • Range from -1.0 to 0 to +1.0

    • Negative correlation vs. positive correlation

    • Necessary in situations where you can’t manipulate variables

Epidemiological Research

  • Type of correlational research

  • Often involves surveys of large groups of people to get a picture of an entire population

  • Study of the incidence, distribution, and consequences of a particular problem or set of problems in one or more populations

Group Experimental Research

  • Nature of experimental research

    • Manipulate the independent variable

    • Observe effects on the dependent variable

    • Attempt to determine causal relationships

    • Premium on internal validity

Clinical Trials

  • Clinical trial: An experiment designed to evaluate the effectiveness of a treatment

  • Control group: Provides a comparison point

    • Often matched to the demographics of the experimental group

    • Placebo control group: some participants are given an inactive treatment (ex., sugar pill), but participants don’t know which treatment they are getting

    • Double-blind control: Participants and assessors are unaware of what kind of treatment participants are getting

  • Placebo effect: Something changes simply because the participant expects the change to occur (ex., expecting to feel better when taking an inactive pill)

  • Comparative treatment research: different treatments are given to two or more groups

Single-Case Experimental Designs

  • Nature of single case design

    • Rigorous study of single cases

    • Manipulate timing and nature of experimental conditions

    • Frequent repeated measurement of outcomes is critical

  • Types of designs:

    • Withdrawal design

    • Multiple baseline design

Studying Genetics

  • Behavioral genetics

    • Interactions of genes, experience, and behavior

    • Genotype: genetic makeup

    • Phenotype: Observable characteristics (ex., eye color, degree of shyness)

    • Endophenotype: Genetic mechanism that contributes to problems causing certain symptoms

  • Family studies

    • Proband: the person who has the trait of interest (ex., someone who has schizophrenia)

    • If there is a genetic influence, expect to see the trait more in first-degree relatives compared to second-degree relatives

    • Familial aggregation: Tendency of a disorder to run in families

    • Issue of shared environment: Families usually live together, so similarities may be due to environmental factors as well as genetics

  • Adoption studies

    • One way to separate the effects of the shared environment

    • Sibling pairs separated after birth: Do they show similarities even if they were raised in different environments?

    • Are adopted children more similar to their birth parents (genetics) or adoptive parents (environment)

  • Twin studies

    • Compare identical/monozygotic twins against fraternal/dizygotic twins

      • If a trait is genetic, expect to see greater concordance in identical twins (similar environment and same genetics) compared to fraternal twins (similar environment, different genetics)

    • Can be combined with adoption studies: if identical twins are both adopted separately and raised apart, shared outcomes are more attributable to genetics

Locating Specific Genes

  • Genetic linkage analysis and association studies

    • Examine known genetic markers (a certain gene whose location is known)

    • Compare these genetic markers against the trait being studied

    • If the genetic marker tends to co-occur with the trait, conclude that the trait is probably caused in part by genes that are in proximity to the genetic marker (ex., on the same chromosome)

    • Genetic linkage studies occur in groups of people who all have the trait of interest

    • Association studies occur in people with and without the trait of interest