Key result
Among 167 RCTs of ADHD medications, 88 defined treatment response using symptom reduction thresholds (most commonly ≥30% reduction in ADHD-RS scores), whereas 79 did not specify any threshold.
Why the study?
The absence of a universal definition of treatment response based on symptom improvement rating scales makes it difficult to compare treatment outcomes across ADHD trials.
How is treatment response defined across randomized controlled trials of ADHD medications?
Systematic Review (n=167)
How is treatment response defined across randomized controlled trials of ADHD medications?
There is significant inconsistency in how treatment response is defined across ADHD medication trials, highlighting the need for a standardized consensus definition.
Heterogeneous response definitions limit cross-trial comparability in ADHD; challenges evidence synthesis and supports consensus criteria for future RCTs.
Objectives:Randomized controlled trials (RCTs) are the gold standard for evaluating medication efficacy. The absence of a universal definition of treatment response, based on the degree of symptom improvement measured by standardized rating scales in the field of attention-deficit/hyperactivity disorder (ADHD), makes it difficult to compare treatment outcomes across RCTs. Here, we aimed to assess to what extent and how “treatment response” is defined across RCTs of ADHD medications. Methods:We identified eligible RCTs via the MED-ADHD database (https://med-adhd.org/), which compiles RCTs evaluating the efficacy and safety of pharmacological treatments for children, adolescents, and adults with ADHD, based on a comprehensive search in multiple electronic databases, including PubMed, BIOSIS Previews, CINAHL, the Cochrane Central Registry of Controlled Trials, and EMBASE, up to 17 January 2025, alongside additional unpublished information gathered from manufacturers/study authors. Results:Out of 167 RCTs in MED-ADHD, 88 defined treatment response based on reductions in ADHD core symptom severity using rating scale scores. The most frequently used threshold was a ≥30% reduction in attention-deficit/hyperactivity disorder (ADHD-RS) scores, with other RCTs using ≥25%, ≥40%, or ≥50%. In addition, RCTs applied similar cutoff values to alternative scales, including Conner’s Adult ADHD Rating Scale, SNAP-IV, Adult ADHD Investigator Rating Scale, and Wender-Reimherr Adult Attention Deficit Disorder Scale. However, 79 studies did not specify any response threshold. Conclusion:Our review underscores and quantitatively defines the inconsistency in the definition of treatment response across ADHD medication trials, highlighting the urgent need for the field to reach a consensus on the use of a standardized definition of “treatment response” for each rating scale, based on the percentage reduction in ADHD core symptom severity.
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Roy et al. (2025) conducted a systematic review in Attention-deficit/hyperactivity disorder (ADHD) (n=167). Pharmacological treatments for ADHD was evaluated on Definition of treatment response based on reductions in ADHD core symptom severity. Among 167 RCTs of ADHD medications, 88 defined treatment response using symptom reduction thresholds (most commonly ≥30% reduction in ADHD-RS scores), whereas 79 did not specify any threshold.
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