single case

Single-Case Experimental Designs for the Evaluation of Treatments for Self-Injurious and Suicidal Behaviors

Authors

  • Shireen L. Rizvi, PhD (The New School for Social Research, New York)

  • Matthew K. Nock, PhD (Harvard University)

Introduction

  • Single-case experimental designs (SCEDs) offer a time- and cost-effective alternative to randomized clinical trials (RCTs) with significant advantages in internal and external validity.

  • This paper provides a primer on SCEDs for use in suicide intervention research.

Qualitative Research Challenges

  • Many potential research obstacles in studies on treatments for suicidal and self-injurious behavior:
      - Low Base Rate of Behaviors:
        - Implications for adequate statistical power; for example, a study wishing to power to detect a moderate effect size of d=0.50d = 0.50 would require 100 participants (Cohen, 1988).
        - Even in urban areas, achieving enrollment can be challenging, with rural settings facing even greater difficulties.
      - High Research Costs:
        - Research often demands large federal grants which can be challenging for junior researchers and graduate students.
      - Methodological Limitations of Group Comparisons:
        - Obfuscation of individual variability, emphasizing between-group differences but losing valuable information about individual progress (Nock et al., 2008; Barlow et al., 2009).

Single-Case Experimental Designs Overview

  • SCEDs distinguish themselves from case studies, which typically lack systematic assessment or experimental manipulation.

  • SCEDs can deliver the same level of experimental rigor as RCTs, often requiring only one participant, thereby demonstrating causal effects efficiently.

  • SCEDs allow for careful examination of between-subject and within-subject factors.

Historical Context of SCEDs

  • Early psychological researchers (Wundt, Ebbinghaus, Pavlov) employed single-subject or small-group methodologies to advance studies on perception, learning, and conditioning (Ebbinghaus, 1885/1913).

  • Behavioral psychology founders also utilized SCEDs to influence research and practice.

  • Underutilization of SCEDs over recent decades due to funding shifts towards large RCTs and advanced data collection methods.

  • The resurgence of SCEDs is proposed to enhance flexibility and efficiency in intervention research.

Primer on SCED Methods

  • Basic Principles of SCEDs:
      1. Identifying Target Behavior: A specific behavior must be reliably and validly measurable.
      2. Continuous Measurement: Regular application of the same measurement to assess changes over time.
      3. Stability of Target Behavior: A stable target behavior is necessary for assessing intervention effects.
      4. Baseline Period: A necessary phase for gathering data before the intervention to establish a comparison point.
      5. Systematic Application of Intervention: Intervention must be applied in a consistent manner, with only the intervention differing between phases.

Design Formats

  1. Basic AB Design:
       - Consists of a baseline period (A) followed by an intervention period (B). While mimicking real-life settings, AB designs have lesser experimental control and are considered weaker.

  2. ABAB Design:
       - Treatment is applied, then withdrawn, followed by reapplication. It helps to demonstrate treatment effects by observing regression towards the baseline.
       - Ethical concerns arise when considering withdrawal of treatment for suicidal individuals; determining feasibility is crucial.
       - Example: Wallenstein and Nock (2007) used an ABAB design to test aerobic exercise for a woman with a history of NSSI, observing significant results and ethical handling.

  3. Quasi-Experimental ABAB Design:
       - Involves natural interruptions or withdrawal of treatment due to practical circumstances, allowing stronger inferences about treatment effectiveness.

  4. Multiple Baseline Designs:
       - Implement treatment sequentially across different individuals or settings, demonstrating how and when treatment affects behavior without removing it (example provided in Rizvi & Linehan, 2005 study).

  5. Changing Criterion Designs:
       - Treatment is modified over time with gradually higher goals or criteria for reinforcement leading to systematic behavior change. An example is utilizing skill reinforcement with a suicidal client to increase positive behavior.

Data Analysis in SCED

  • Analysis generally relies on visual inspection along four criteria:
      1. Change in mean rate of behavior from baseline to intervention.
      2. Change in slope from baseline to intervention phases.
      3. Shift in responses from baseline to intervention levels.
      4. Small latency to change reflecting swift effects when transitioning from one phase to another.

  • Emphasis is placed on clinical significance, especially in suicidal behaviors, where mere reduction in frequency may not suffice as a success metric.

Applications of SCED in Suicide Intervention Research

  • SCEDs facilitate a focus on individual-level changes rather than group averages, allowing for nuanced evaluation of treatments.

  • Incorrect assumptions about behavior can be avoided due to the detailed tracking of numerous data points over time.

  • They necessitate fewer participants, majorly benefiting researchers by reducing recruitment time and costs.

  • They also allow for testing novel hypotheses or evaluations before larger trials.

Ethical Considerations

  • Ethical concerns regarding treatment withdrawal during baseline or ABAB designs must be proactively managed to protect vulnerable populations.

  • Alternatives include maintaining treatment-as-usual during baseline or designing alternating treatments to minimize withholding interventions.

Limitations of SCED Methodology

  • Establishing a stable baseline can be particularly challenging in assessing high-risk behaviors, as behaviors may fluctuate highly.

  • Adjustments may be required, such as targeting ideation rather than attempts for improved stability in research parameters.

  • Transparency in SCEDs forces vigilance in treatment efficacy analyses, avoiding oversight but disclosing potential treatment failures.

Future Directions in Suicide Intervention Research

  • Research Support for Psychosocial Treatments:
      - Empirical backing for treatments like Dialectical Behavior Therapy (DBT) and Cognitive Therapy (CT) can further be explored through SCEDs.

  • The exploration of treatment mechanisms remains underdeveloped; SCEDs can help isolate active components of treatments.
      - Example: By evaluating individual DBT modules' impacts on suicidal behavior, researchers can determine critical treatment ingredients and their sequences.

Conclusion

  • SCEDs present a viable research methodology that, when thoughtfully applied, can unveil effective interventions for self-injurious and suicidal behaviors. Their utilization in future research is encouraged for ethical treatment development.