Investigating Alexithymia as a Moderator of Outcomes in a Randomized Controlled Trial of an Online Intervention for Co-Occurring Depression and Hazardous Alcohol Use: Enquête sur l'alexithymie en tant que modérateur des résultats dans un essai randomisé contrôlé d'une intervention en ligne pour la dépression concomitante et la consommation dangereuse d'alcool.

Objective: Alexithymia is characterized by difficulty identifying and/or describing emotions, reduced imaginal processes, and externally oriented thinking. High levels of alexithymia may increase the challenge of supporting individuals with co-occurring depression and hazardous alcohol use. This secondary analysis sought to investigate whether or not alexithymia moderated the outcomes of an online intervention for depression and alcohol use.

Method: As part of a randomized controlled trial, 988 participants were randomly assigned to receive an intervention dually focused on depression and alcohol use, or an intervention only focused on depression. The pre-specified mediation hypothesis was that changes in drinking at 3 months follow-up would effect the association between the intervention and change in depression at 6 months. This secondary analysis extends the investigation by adding alexithymia as a moderator.

Results: The current analysis demonstrated that including alexithymia as a moderator resulted in a conditional direct effect. Specifically, there was an intervention effect where participants who received the combined depression and alcohol intervention had larger improvements in their depression scores at 6 months, but this was only when their alexithymia score at baseline was also high (60.5 or higher).

Conclusion: These results suggest that treatment planning and intervention effectiveness could be informed and optimized by taking alexithymia severity into consideration. This is especially merited as alexithymia can contribute to the weaker therapeutic alliance, more distress and dysphoria, shorter periods of abstinence, and more severe depression, compounding the complexity of supporting individuals with comorbid conditions. More research is needed to systematically investigate these possible modifying effects.

Plain Language Title: Does difficulty identifying/describing emotions or externally-oriented thinking influence the effectiveness of an intervention among people with both depression and hazardous alcohol use?