What do alexithymia items measure? A discriminant content validity study of the Toronto-alexithymia-scale–20

Background
Questions have been raised about whether items of alexithymia scales assess the construct alexithymia and its key features, and no other related constructs. This study assessed the (discriminant) content validity of the most widely used alexithymia scale, i.e., the Toronto Alexithymia Scale (TAS-20).

Methods
Participants (n = 81) rated to what extent TAS-20 items and items of related constructs were relevant for assessing the constructs ‘alexithymia’, ‘difficulty identifying feelings’, ‘difficulty describing feelings’, ‘externally-oriented thinking’, ‘limited imaginal capacity’, ‘anxiety’, ‘depression’, and ‘health anxiety’.

Results
Results revealed that, overall, the TAS-20 did only partly measure ‘alexithymia’. Only the subscales ‘difficulty identifying feelings’ and ‘difficulty describing feelings’ represented ‘alexithymia’ and their intended construct, although some content overlap between these subscales was found. In addition, some items assessed (health) anxiety equally well or even better.

Conclusions
Revision of the TAS-20 is recommended to adequately assess all key features of alexithymia. Findings with the TAS-20 need to be interpreted with caution in people suffering from medical conditions.