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-l) 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.