Alexithymia in post-traumatic stress disorder is not just emotion numbing: Systematic review of neural evidence and clinical implications.

• PTSD with alexithymia and PTSD-related emotion numbing show unique neural profiles. • Alexithymia is linked to alterations in the default mode network. • Alexithymia is associated with emotional meta-cognition and attentional control. • PTSD-related emotion numbing is linked to alterations in the salience network. • Emotion numbing is linked to disorder-level negative affect. Alexithymia is very common among those with Post-traumatic stress disorder with estimates suggesting that as many as 42% of individuals with PTSD exhibit clinically-relevant alexithymia. One proposed explanation for this comorbidity is that alexithymia symptoms exhibit structural overlap with PTSD-related emotion numbing. Given the need to identify via objective measurement whether alexithymia and emotional numbing are overlapping or different experiences, a review of neural circuitry involved in these conditions is warranted. In this paper, we briefly discuss emotion processing in Alexithymia and PTSD, presenting a PRISMA systematic review of the relevant functional neuroimaging studies. Our results suggest that alexithymia is linked to alterations in the Default Mode Network (DMN) while PTSD-related emotion numbing appears to be primarily linked to alterations in the salience network. Our results suggest that emotion numbing may be linked to neural networks associated with disorder-level negative affect while alexithymia is linked to alterations in neural networks associated with emotional meta-cognition and attentional control, providing evidence that these constructs are at least partially distinct in the brain. This has important clinical implications and may inform the selection of appropriate treatments. The impact of the review may be limited due to cross-study variations in control groups, different trauma histories, individual differences and emotion processing paradigms utilised.