Measuring Psychological Inflexibility of Suicidal Thoughts: The Acceptance and Action Questionnaire for Suicidal Ideation (AAQ-SI)

Background Despite interest in psychological inflexibility as a marker of suicide risk, no measure of psychological inflexibility specific to SI exists. Methods The present study utilized data from two internet- and one lab-based sample to establish and evaluate such a measure, the Acceptance and Action Questionnaire for Suicidal Ideation (AAQ-SI). Reliability analysis of seven initial items identified four items in Sample 1 that measured this construct. Results Confirmatory factor analysis demonstrated a one-factor solution fit these data in Samples 1 and 2. AAQ-SI scores demonstrated convergent validity (i.e., bivariate correlations) in all samples with another measure of general psychological inflexibility and measures of SI intrusiveness, avoidance, and comfort. AAQ-SI scores demonstrated a statistically significantly weaker correlation with depression symptoms compared to a measure of general psychological inflexibility in Sample 2. AAQ-SI scores were uniquely statistically significantly associated with SI severity in separate regression models within each sample, while an existing measure of general psychological inflexibility was not. Conclusions The AAQ-SI appears to be an appropriate measure of psychological inflexibility specific to the experience of suicidal thoughts. Clinicians and researchers interested in this construct among suicidal individuals may opt for the AAQ-SI over other alternatives.