Serotonin transporter gene promoter polymorphism and somatoform symptoms

Symptoms of somatoform and affective disorders are thought to be connected to serotonergic neurotransmission because serotonin is known to regulate the functions relevant in these disorders, such as pain and mood. Previous studies have reported associations of these disorders with a functional polymorphism in the promoter region of the serotonin transporter gene, a limiting factor of the serotonergic neuronal system, as its alleles have been associated with differences in levels of synthesized transporter and therefore differences in reuptake efficiency.

Ninety-one patients with at least 2 unexplained physical symptoms were clinically evaluated and genotyped for the triallelic genotypes of the serotonin transporter gene polymorphism; patients were recruited from 2001 until 2004. DSM-IV diagnoses were assessed using the International Checklists for ICD-10 and DSM-IV. Somatic complaints were quantified with an interview version of the Screening for Somatoform Symptoms, persistent symptoms in the last 2 years (SOMS-2) and the SOMS-7 (current symptoms in the last 7 days). Depressive symptoms were quantified with the Beck Depression Inventory (BDI).

Subjects with higher-expressing allele variants of the serotonin transporter gene (L'L' and L'S') had significantly more somatic symptoms in the last 2 years (trait) than those with lower-expressing variants (S'S') (P < .01). No differences could be found in regard to short-term somatic symptoms (ie, in the last 7 days). Neither depressive symptoms nor a comorbid diagnosis of major depression was associated with allelic variants.

Somatoform symptoms may be associated with a functional polymorphism in the promoter region of the serotonin transporter gene.