Differential Relationships among Facets of Alexithymia and BDNF- and Dopamine-Related Polymorphisms

Alexithymia refers to a cluster of emotion-related deficits such as difficulty attending to and identifying one’s feelings. Although not a diagnosable psychiatric condition, alexithymia is considered a personality risk factor for multiple pathologies, including somatoform, substance use, eating, and mood disorders. Evidence suggests heritability, but few studies have examined the influence of specific genes on alexithymic traits. Candidate genes explored thus far include those involved in modulation of brain-derived neurotrophic factor (BDNF) and dopamine, two neurotransmitters whose functions have been implicated in human emotion processing. This study investigated the relationship between the C270T polymorphism of the BDNF gene, facets of alexithymia, and possible interactions with the COMT, DAT1, and ANKK1 genes in a sample of 130 healthy adults. Given the multidimensionality of the alexithymia construct and its overlap with the related constructs of emotional intelligence and mood awareness, we used principal components analysis to derive Clarity of Emotion and Attention to Emotion as specific facets of alexithymia. Results showed that the C270T C/C genotype group had lower Clarity of Emotion scores relative to the C/T genotype group, even after covarying for COMT, DAT1, and ANKK1 genotypes. Dopamine-related genes had no association with alexithymia dimensions, nor did they interact with the C270T polymorphism to predict Clarity of Emotion. Although the molecular mechanisms by which this polymorphism influences BDNF are unknown, this study suggests a role for BDNF in modulating aspects of alexithymia. We discuss these results in the context of BDNF’s trophic effects in the nervous system.