Securing an accurate autism-spectrum-condition diagnosis, particularly among women, remains challenging for autistic adults. Building upon previous research highlighting the short-story task (SST) as a promising tool for detecting fiction-based mentalizing difficulties in autistic adults, this study expands its scope. We investigated the SST's discriminative capacity across three distinct groups: autistic individuals (n = 32), nonautistic individuals without mental health problems (n = 32), and nonautistic individuals with clinical depression (n = 30). All three groups differed significantly from each other in their SST mentalizing score with the nonautistic group having the highest scores, the nonautistic but depressed group having medium scores and the autistic group showing the lowest scores. Receiver operator curve (ROC) analysis reaffirmed the SST's efficacy as a discriminator. Moreover, a linear regression analysis identified the SST mentalizing score, the SST comprehension score, and the number of books read per month as significant predictors of autism-spectrum-condition diagnosis. These findings bolster the SST's potential as a valuable adjunct in autism diagnostics, highlighting its discriminatory ability across diverse samples.