Effect Size Magic: A Conversation With Leslie L. Citrome, MD, MPH

TALKING WITH TITANS

At the 2026 American Society of Clinical Psychopharmacology (ASCP) Annual Meeting in Miami, FL, Psychiatric Times' Editor in Chief, John J. Miller, MD, sat down with leaders in the field to discuss the topics they find most important.

Leslie L. Citrome, MD, MPH, won the Henry Nasrallah Award for Excellence in Clinical Psychopharmacology Education at this year’s ASCP Annual Meeting.

Citrome discussed with Miller his Lifetime Awardee presentation, “The Tyranny of the P-value: Effect Size Matters,”¹ and the importance of understanding effect size over P-values. According to Citrome, the “tyranny of the P” can lead researchers astray and allow irrelevant findings to be published. Citrome believes that in order to quantify the clinical importance of a statistically significant result, the effect size must be calculated. Effect size is becoming more common in FDA-regulated presentations,² often mentioned as a standardized mean difference. Citrome also expanded on Cohen’s d, which is measured in standard deviation units and provides a range of significance (0.2, 0.5, 1.0).

He also shared that the number needed to treat (NNT) is the most intuitive measure, and the simplest to calculate. Citrome emphasized that a lower NNT indicates a more effective treatment, while a higher NNT suggests a less effective one. Individualizing treatment choices based on NNT values is recommended.

He also introduces the concept of number needed to harm (NNH) to assess adverse effects. Both metrics are crucial for evidence-based medicine, alongside clinical experience and patient values. Citrome explains the significance of comparing NNT and NNH to make informed treatment decisions.

Clinicians must integrate clinical experience, scientific evidence, and patient values when making treatment decisions. Evidence-based practice involves considering all 3 components to achieve the best outcomes for individual patients. He concluded with the concept of an "n of 1" study, where treatment decisions are tailored to the specific patient's response.

Dr Miller is Medical Director, Brain Health, Exeter, New Hampshire; Editor in Chief, Psychiatric Times; Volunteer Consulting Psychiatrist, Seacoast Mental Health Center, Exeter; Consulting Psychiatrist, Insight Meditation Society, Barre, Massachusetts.

Dr Citrome is a clinical professor of psychiatry and behavioral sciences at New York Medical College. He is a distinguished life fellow of the American Psychiatric Association and a fellow of the American Society of Clinical Psychopharmacology, where he currently serves as immediate past president. He is also currently a consultant in clinical trial design and interpretation.

References

1. Citrome L. The tyranny of the P-value: effect size matters. Presentation at: 2026 ASCP Annual Meeting; May 26-29; Miami Beach, FL. Accessed May 15, 2026.

2. Multiple endpoints in clinical trials: guidance for industry. FDA. January 2017. Accessed May 28, 2026. https://www.fda.gov/files/drugs/published/Multiple-Endpoints-in-Clinical-Trials-Guidance-for-Industry.pdf