Major depression, 5HTTLPR genotype, suicide and antidepressant influences on thalamic volume

Background: The 5HTTLPR genetic variant of the serotonin transporter gene (SERT or 5-HTT), which is comprised of a short (SERT-s) and a long (SERT-I) allele, is associated with major depressive disorder and post-traumatic brain disorder. Aims: The present study sought to determine whether the total thalamus and major subregions are altered in size in major depressive disorder and in relation to the 5HTTLPR genotype. Method: We investigated the influence of 5HTTLPR genotype, psychiatric diagnosis, suicide and other clinical factors on the volume of the entire post-mortem thalamus. Results: Major depressive disorder, SERT-ss genotype and suicide emerged as independent factors contributing to an enlargement of the total thalamus. The majority of the volume enlargement associated with the SERT-ss genotype occurred in the pulvinar, whereas enlargement associated with major depressive disorder occurred in the limbic nuclei and in other regions of the thalamus. A history of antidepressant treatment was associated with reduced thalamic volume. Conclusions: The 5HTTLPR genetic variation may affect behaviour and psychiatric conditions, in part, by altering the anatomy of the thalamus. Declaration of interest: None. Funding detailed in Acknowledgements.