Serotonin transporter polymorphisms (5-HTTLPR) in emotion processing: Implications from current neurobiology

• Candidate gene studies are based on ongoing biological studies.
• Etiological hypothesis in serotonin transporter polymorphism research.
• Neural plasticity and clinical implications.

The candidate gene approach directly tests the effects of genetic variation within a potentially contributing gene in an association study. However, the candidate gene approach is limited by how much is known about the biology of the disease being investigated. The serotonin transporter gene SLC6A4 has been studied more than any other single candidate gene in the field of neurobiology. Transcription of the serotonin transporter gene is modulated by a polymorphic region, 5-HTTLPR, near the promoter. 5-HTTLPR genotype has been associated with individual variation in emotion processing, brain structure, and brain function. We present an updated review of the biological literature on the serotonin transporter polymorphism. Recent imaging and behavioral studies of the role of 5-HTTLPR genotype in emotion processing are discussed in light of new biological findings related to 5-HTTLPR variation. We also examine the clinical implications of discoveries about the role of serotonin and 5-HTTLPR genotype in neural plasticity and behavioral malleability.