The Suicidal Ideation Attributes Scale-Modified (SIDAS-M): Development and preliminary validation of a new scale for the measurement of suicidal ideation in autistic adults

The study describes the development and preliminary psychometric validation of the Suicidal Ideation Attributes Scale-Modified (SIDAS-M), a five-item assessment of suicidal ideation for use with autistic adults. Participants (n = 102 autistic adults; 58% women, 34% men, 8% nonbinary; M-age = 41.75, SD = 12.89) completed an online survey including the SIDAS-M at Time 1 and participated in follow-up interviews at Time 2 (similar to 111 days later). A single factor solution provided good to excellent fit to the data (comparative fit index = 0.961, Tucker-Lewis index = 0.921; standardized root mean square residual = 0.027), with all items showing good to excellent loadings (0.74-0.91). SIDAS-M total score (omega=.930, bias-corrected and accelerated 95% confidence interval (BCa 95% CI) [.90, .95]) demonstrated good convergent validity, correlating significantly with existing suicide specific (rho=.442-.698, p<.001) and well-being measures (rho=.325.-.505, p <=.001), and good divergent validity. Logistic regression controlling for age, gender, and relationship status indicated that SIDAS-M scores at Time 1 significantly predicted suicidal behavior at Time 2, beta = 0.462, p < 0.001, [0.032, 0.068]. Receiver operating characteristic curve analysis indicated SIDAS-M has utility discriminating between participants classified at low or above low risk, area under the curve = 0.866, [0.767, 0.966], p < 0.001, with a cutoff score >= 1 providing a potentially useful indicator of increased suicidal risk. Overall, SIDAS-M demonstrated good psychometric properties when used with autistic adults without intellectual disability.