Commentary: Alexithymia, not autism, is associated with impaired interoception

Alexithymia is characterized by difficulties in recognizing and reporting on one's own emotions (Nemiah et al., 1976). There is growing interest in alexithymia in Autism Spectrum Disorder (ASD) since at least 50% of those with ASD experience co-occurring alexithymia (Hill et al., 2004). Impaired interoception, that is problems with perceiving one's internal bodily signals, is a candidate mechanism underlying alexithymia (Herbert et al., 2011). However, interoceptive difficulties have also been implicated in ASD. It is therefore contentious whether alexithymia, ASD or both are linked to poor interoception (Brewer et al., 2015). A new study published in Cortex addresses this issue, concluding that alexithymia, not autism, is related to interoceptive impairment (Shah et al., 2016). In light of this, the role of alexithymia in emotional and interoceptive difficulties in ASD and arising clinical implications are discussed. Bird and Cook's (2013) alexithymia hypothesis proposes that emotional problems observed in ASD are attributable to co-occurring alexithymia, rather than ASD itself. This arose from the findings that difficulties with empathy (Bird et al., 2010), emotional recognition (Cook et al., 2013) and attention to the eyes (Bird et al., 2011) are not associated with ASD after controlling for alexithymia. More recently, in elucidating the overlap between alexithymia and ASD, attention has turned to interoception. Quattrocki and Friston (2014) propose that early disturbance in oxytocin-mediated interoception promotes a developmental cascade of problems in representing emotional states, hence alexithymia. Although this model set out to explain all ASD symptomatology, Brewer et al. (2015) have extended the alexithymia hypothesis by arguing that where emotional symptoms are seen in ASD due to impaired interoception, these may be underpinned by co-occurring alexithymia. Shah et al. (2016) quantified the distinct contributions of alexithymia and autism to interoceptive accuracy specifically, by instructing participants to count their own heartbeats within varying time frames, whilst actual heartbeat signals were recorded simultaneously. Across clinical and non-clinical populations, alexithymia, but not autism, was associated with poorer interoceptive accuracy. Crucially, the fact that individuals with and without ASD displayed comparable interoceptive accuracy when matched for alexithymia suggests that interoceptive atypicalities, when observed in ASD, are alexithymia-specific, which corroborates the alexithymia hypothesis. Furthermore, alexithymia predicted interoceptive accuracy over and above anxiety, depression and Body Mass Index, all of which may be related to interoception (Craig, 2014). Shah and colleagues' findings add to growing evidence that the abilities to perceive your own emotions and bodily signals are tightly coupled …