Proving a negative? Methodological, statistical, and psychometric flaws in Ullmann et al. (2017) PTSD study

Area of Science:

• Endocrinology
• Psychiatry
• Urology

Background:

• Male circumcision is a common procedure with ongoing debate regarding potential long-term psychological effects.
• The hypothalamic-pituitary-adrenal (HPA) axis is a key regulator of the stress response.
• Hair cortisol and cortisone levels are increasingly used as biomarkers for long-term stress exposure.

Purpose of the Study:

• To investigate potential long-term psychopathological effects of male circumcision by examining hair cortisol and cortisone levels.
• To assess the functionality of the HPA axis in circumcised versus non-circumcised men.

Main Methods:

• A pilot study comparing hair cortisol and cortisone levels in circumcised men and genitally intact (non-circumcised) men.
• Analysis of hair samples to measure levels of cortisol and cortisone, serving as biomarkers for chronic stress.
• Statistical analysis to determine significant differences between the two groups.

Main Results:

• The study reported no statistically significant reduction in hair cortisol or cortisone levels in circumcised men compared to non-circumcised men.
• The authors interpreted these null findings as evidence against long-term psychopathological effects of circumcision.
• The authors also claimed evidence for healthy HPA axis functionality in circumcised individuals.

Conclusions:

• The authors' conclusions regarding the refutation of psychopathological effects and healthy HPA axis functionality are not supported by the null findings of this underpowered pilot study.
• The study's limitations, including potential underpowering, suggest that the observed trends might indicate opposite effects in a larger, adequately powered study.
• Weaknesses in study design, measurement, and interpretation further undermine the authors' strong claims, indicating their conclusions are not data-supported.