Exploring Candidate Gene Studies and Alexithymia: A Systematic Review.

Abstract

Alexithymia is a trait involving difficulties in processing emotions. Genetic association studies have investigated candidate genes involved in alexithymia's pathogenesis. Therefore, the aim of the present study was to perform a systematic review of the genetic background associated with alexithymia. A systematic review of genetic studies of people with alexithymia was conducted. Electronic databases including PubMed, Scopus, and Web of Science were searched for the study purpose. We used the words "Alexithymia", "gene", "genetics", "variants", and "biomarkers". The present systematic review was performed following the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement. We found only candidate gene studies. A total of seventeen studies met the eligibility criteria, which comprised 22,361 individuals. The candidate genes associated with alexithymia were the serotoninergic pathway genes solute carrier family 6 member 4 (SLC6A4), serotonin 1A receptor (HTR1A), and serotonin 1A receptor (HTR2A); the neurotransmitter metabolism genes dopamine receptor D2 (DRD2), ankyrin repeat and kinase domain containing 1 (ANKK1), catechol-o-methyltransferase (COMT), brain-derived neurotrophic factor (BDNF), and oxytocin receptor (OXTR); and other pathway genes, vitamin D-binding protein (VDBP), tumor protein P53 regulated apoptosis inducing protein 1 (TP53AIP1), Rho GTPase Activating Protein 32 (ARHGAP32), and transmembrane protein 88B (TMEM88B). The results of this study showed that only case-control gene studies have been performed in alexithymia. On the basis of our findings, the majority of alexithymia genes and polymorphisms in this study belong to the serotoninergic pathway and neurotransmitter metabolism genes. These data suggest a role of serotoninergic neurotransmission in alexithymia. Nevertheless, more and future research is required to learn about the role of these genes in alexithymia.