Two clinical trial designs to examine personalized treatments for psychiatric disorders

Area of Science:

• Psychiatry and Mental Health
• Clinical Trial Design
• Personalized Medicine

Background:

• The National Institute of Mental Health (NIMH) strategic plan emphasizes personalized treatment for mental disorders.
• Exploratory analyses of existing randomized controlled trial (RCT) data identify potential moderators of treatment effects.
• Hypothesis generation from exploratory analyses necessitates independent replication through confirmatory RCTs.

Purpose of the Study:

• To describe two general approaches for designing confirmatory RCTs that build upon exploratory findings.
• To compare the distinct questions and hypothesis-testing strategies of factorial and main effects designs.
• To analyze the impact of design choice on sample size, cost, duration, and generalizability.

Main Methods:

• Description of a 2x2 factorial design to test moderator-by-treatment interactions.
• Description of a main effects strategy to evaluate interventions in subgroups.
• Comparison of sample size requirements and resource implications for each design.

Main Results:

• Factorial designs directly test differential treatment effects via interaction, requiring significantly larger sample sizes (up to 4-fold).
• Main effects strategies test treatment within subgroups separately.
• Design choice critically influences research costs, trial duration, subject exposure, and result generalizability.

Conclusions:

• The 2x2 factorial design is preferable for identifying personalized interventions when resources are ample, due to its direct testing of differential effects.
• Main effects strategies may be more feasible with limited resources but offer less direct evidence of personalized treatment.
• Careful consideration of design impacts is crucial for efficient and effective development of personalized mental health treatments.