Readability of informed consent forms from ClinicalTrials.gov in ketamine clinical trials for mental health conditions: a cross-sectional analysis
Damian Swieczkowski, Aleksander Kwaśny, Wiesław Jerzy CubałaBackground:
Ensuring participants understand informed consent forms (ICFs) is a core ethical requirement of clinical research, particularly in psychiatry, where cognitive and affective symptoms can compromise decisional capacity. As ketamine-based interventions are increasingly studied for mental health conditions, the readability of consent materials in these trials warrants systematic evaluation.
Objectives:
To assess the readability and linguistic complexity of ICFs from ClinicalTrials.gov used in ketamine clinical trials for mental health conditions.
Design:
Cross-sectional analysis.
Methods:
We conducted a cross-sectional analysis of English-language ICFs posted on ClinicalTrials.gov for interventional ketamine clinical trials involving mental health conditions. All documents were converted to plain text and standardised for text-based analysis. Readability and linguistic complexity were assessed using established indices, including the Flesch–Kincaid Grade Level, Gunning Fog Index, Flesch Reading Ease Score, and Fry Readability Graph. Document length and estimated silent reading time were also calculated. Descriptive statistics summarised the findings.
Results:
Fourteen ketamine clinical trials met the inclusion criteria. ICFs ranged from 1681 to 8637 words (mean: 5031; median: 4622), with sentence counts from 129 to 503. Estimated silent reading times ranged from 7.0 to 36.0 min (mean: 21.4; median: 19.5). Flesch–Kincaid Grade Level scores ranged from 5.7 to 11.5 (mean: 9.8), with 13 of 14 documents above grade 8. Gunning Fog Index values ranged from 7.7 to 13.8 (mean: 11.7). Flesch Reading Ease Scores ranged from 41.3 to 73.9 (mean: 52.8). Fry Readability scores ranged from grade 6 to grade 13.
Conclusion:
Thirteen of fourteen ketamine mental health trial consent forms on ClinicalTrials.gov exceeded recommended readability thresholds. Sponsors and ethics committees should require consent materials to meet an eighth-grade reading level, verified by a documented readability assessment before approval, to support informed participation in psychiatric research.