Predictive Discriminant Validity of the 20-Item Toronto Alexithymia Scale: Incremental Prediction of Emotion Regulation Beyond Psychological Distress

Several factor analytic investigations question whether the 20-item Toronto Alexithymia Scale (TAS-20) discriminates alexithymia from general psychological distress, with some researchers concluding that the difficulty identifying feelings (DIF) subscale measures distress rather than alexithymia. This debate has focused almost exclusively on structural discriminant validity (i.e., factor analytic analyses) while neglecting predictive discriminant validity, or whether alexithymia predicts clinically relevant outcomes relatively independent of distress. The present study addressed this issue using hierarchical multiple regression in a community sample enriched with participants having psychiatric histories (N = 661). Emotion regulation was assessed across three domains: global emotion dysregulation (DERS), maladaptive and adaptive cognitive strategies (CERQ), and behavioral strategies (BERQ). After controlling for depression, anxiety, and stress (DASS-21), the TAS-20—entered as its three subscales (DIF, DDF, EOT)—retained statistically significant incremental prediction across all five emotion regulation outcomes. Increments were largest for global emotion dysregulation (ΔR2 = 0.11) and behavioral regulation (ΔR2 = 0.10 adaptive, 0.09 maladaptive), and smallest for cognitive regulation outcomes (ΔR2 = 0.02 adaptive, 0.03 maladaptive); none reached the 0.15 heuristic for a clinically meaningful incremental validity, but all were statistically reliable and obtained against a deliberately conservative test in which alexithymia–distress overlap was partialed prior to entry. Among the subscales, difficulty describing feelings (DDF) and externally oriented thinking (EOT) emerged as the most consistent unique predictors across outcomes after distress control, whereas DIF showed greater attenuation. Notably, a domain-level dissociation emerged whereby alexithymia was the stronger unique predictor of behavioral regulation outcomes while distress showed comparatively greater unique prediction of cognitive strategies, suggesting the two constructs contribute to emotion regulation impairment through partially distinct pathways. These findings support the predictive discriminant validity of the TAS-20: the instrument captures incremental variance in emotion regulation that is statistically reliable across domains and theoretically coherent in its facet-level patterning, even as the construct shows some understandable overlap with concurrent psychological distress.