Experimental Clinical Psychology Lessons 19-20

Experimental Clinical Psychology

• This is a course on experimental methods in clinical psychology, covering lessons 19 and 20.

RCTs – Design Considerations

• Selection of control conditions: Crucial for comparing treatment effectiveness.
• Randomization: Ensures participants have an equal chance of being in any group, but does not guarantee comparability. Random assignment is important but chance can prevent the groups from being truly equivalent.
• Evaluation of treatment response across time: Evaluates treatment efficacy at different stages (e.g., pre-treatment, post-treatment, follow-up).
• Comparison of multiple treatments: Compares the efficacy of different therapies or treatments, highlighting their relative differences.
• Random Assignment: Ensures each participant has equal chance in being placed in a treatment condition or control condition. It does not, however,guarantee that groups are comparable.
• Problems when random assignment is not incorporated in the design:
  • Prestudy differences
  • Selection bias (e.g., patients choosing active treatment or waiting list)
• Randomized blocks assignment (stratified blocks): A method to enhance comparability across conditions by matching participants based on characteristics.
  • Matching subgroups of participants that highly comparable; subgroups determined by measurable traits; number of participants per subgroup equals the number of groups/conditions.
  • Membership of each subgroup is randomly assigned.

Assessment of Treatment Response Across Time

• Timepoints for evaluation:

  • Pretreatment (baseline)
  • Posttreatment (acute treatment efficacy)
  • Follow-up (maintenance or continued improvement).

• Baseline assessment: Critically important to establishing comparability between groups

• Posttreatment assessment: Crucial to determine efficacy/acute effects and comparing to baseline.

• Post-treatment efficacy does not guarantee maintenance (long-term effects): Follow-up is needed

• Follow-up periods: Various lengths are suggested (e.g., 6, 9, 12, or 18 months).

RCTs - Multiple Treatment Comparisons

• Comparative (relative) efficacy of therapy: Comparative research aims to determine which treatment is more effective than an alternative. A between groups design is used when there is more than one condition (treatment group).
• Smaller effect sizes: Multiple treatment comparisons often yield smaller effect sizes than single treatment comparisons. This impacts study design and considerations concerning acceptable levels of difference.
• Larger samples of participants: Needed to detect smaller effect differences between conditions.
• Comparability across therapists: Matching therapists in terms of training, experience, and interventions to control biases
  • Therapists should conduct each intervention equally well and have an unbiased approach.
  • Stratified blocking is necessary for effective control.
• Intervention procedures across conditions:
  • Duration of intervention(Length, intensity, and frequency of contact with the patient)
  • Treatment credibility
  • Treatment setting(E.g., location of the therapy)
  • Involvement of other significant people (e.g., family)
• Issues related to measures of change: Define expected outcomes, ensuring outcome measures are sensitive to interventions, and use intervention-specific measures
  • Expected outcomes are defined explicitly; outcome measures should demonstrate responsiveness to expected interventions; the measure used should be specific to the intervention.

Overview: RCTs - Procedural Considerations

• Sample selection:
  • Genuine clinical sample
  • Analogue sample
  • Highly selected sample. Considering this difference in sample selection criteria affects how easily participants can be recruited, level of control over confounding factors (important to determine internal validity), and the potential threat to external validity.
• Study setting: Considerations in the research setting, particularly if it's a research center vs. clinical practice, can affect the external validity and generalizability of results.
• Independent Variable Definition:
  • Treatment manuals are important, providing standardization.
  • Manuals also allow for replication; teaching (training and mentorship).
  • Manuals are critical for increased internal validity and treatment integrity; reduce potential confounders (e.g., therapist expertise).
  • While manuals restrict creativity and individualization of care, empirical evidence shows they don't greatly affect therapist flexibility.

RCTs - Integrity of the Independent Variable

• Why check? Random assignment doesn't guarantee the treatment was implemented correctly. Issues include insufficient therapist training, lack of manual specification, and inadequate monitoring.

• Supervision and monitoring:

  • Supervision is needed throughout the study.
  • Audio-video recording is a way to record sessions for external review.
  • Independent ratings and adherence measurements are key aspects of verifying intervention integrity.
  • Independent quality assessment and adherence are required for validation

• Treatment Integrity:

  • Raters use checklists to assess reliability during sessions (video recordings, etc.)
  • Procedures were used, and the content/strategies were followed.
  • High reliability, meaning there is agreement between ratings by different raters.

RCTs - Measurement Considerations

• Multi-informant/Multi-modal strategy: Use multiple sources of data to evaluate outcomes.
  • Self-report, tests/tasks, therapist ratings, archival records, ratings by blind experts, significant people.

RCTs - Data Analysis

• Missing data & Attrition:

  • Attrition: Loss of participants at various points(randomization/treatment/evaluations)
  • Reasons for attrition: Various/potential reasons
  • Handling attrition: Various methods; e.g., completers analysis and intent-to-treat analysis.
    • Completers analysis—risk of bias due to the reasons for why participants drop out
    • Intent-to-treat analysis – conservative approach and avoids bias; more robust and often preferred
  • Methods to address missing data: Last observation carried forward, substituting pretreatment scores, multiple imputation methods, or mixed-effects modeling.

• Clinical significance: Evaluate the meaningfulness or importance of magnitude of change. Note the difference between statistical significance (due to chance) and the meaningfulness of results.

• Moderators and Mediators:

  • Moderators: Factors that influence strength/direction of the treatment-outcome relationship based on how a treatment will work best
  • Example: identify when treatments have different effects, the circumstances under such different outcomes, and how influences treatment effectiveness(strength/direction)
  • Mediators: Factors that illustrate mechanisms through which a treatment operates.
  • Example: identifies how and why treatments produce effects; provides a causal model linking treatment and outcome; this helps in understanding how treatment produces effects

This quiz covers key concepts from lessons 19 and 20 of the Experimental Clinical Psychology course. Focus areas include randomized control trials, treatment comparisons, and evaluation of treatment efficacy over time. Test your understanding of experimental methods and design considerations in clinical psychology.