The association between overcommitment to work and depressive symptoms is moderated by the polymorphic region of the 5-HTT gene.

Overcommitment (OC) to work is a prevalent personality trait characterized by the inability to withdraw from obligations combined with a high need for control and approval. Over committed individuals are extremely ambitious and tend to repeatedly exaggerate their efforts while at the same time over taxing their resources (Siegrist et al., 2004). Epidemiological studies in apparently healthy employees suggest that OC is associated with depressive symptoms, most likely in a prospec tive way (e.g. Niedhammer et al., 2004). Genetic polymorphisms at the serotonin transporter locus have been associated with alterations in brain serotonin turnover in major depressive disorder (MDD). MDD patients carrying the short (s) allele of the 5 HTTLPR showed increased brain serotonin turnover compared to those carrying the long (l) allele at this locus (Barton et al., 2008). Brain serotonin turnover was normalized following medication therapy using selective serotonin reuptake inhibitors (SSRI) accompanied by improvement in depression symptoms (Barton et al., 2008). We investigated whether OC is differentially associated with depressive symptom severity in subjects character ized for 5 HTTLPR gene polymorphisms in a sample including MDD patients. We hypothesized that the HTTLPR genotype moderates the level of OC and depressive symptom severity in individuals with and without clinical depression. We recruited 115 consecutively admitted inpatients with recurrent unipolar depression (DSM IV) aged 18 60 years from the Psychiatry Department of the Bonn University and 178 age and gender matched healthy volunteers without psychopatholo gical symptoms from the general population living in the same region. OC was assessed by a uni dimensional scale composed of six Likert scaled items for which respondents indicated to what extent they personally agreed or disagreed with the given state ments on a four point rating scale ranging from 6 to 24 with higher scores reflecting higher OC (Siegrist et al., 2004). Depressive symptom severity was assessed with the 21 item Beck Depression Inventory (BDI) where scores Z10 indicate possible clinical depression. Effort Reward imbalance (ERI) assesses stressful experience at work by means of a 17 item questionnaire consist ing of two scales measuring a ratio between perceived efforts and experienced or anticipated rewards (Siegrist et al., 2004). All of the questionnaires have been widely used and showed good internal consistency and validity. We assessed the length poly morphism in the promoter region of the serotonin gene (5 HTTLPR) and the single nucleotide polymorphism rs25531 and reclassified the obtained genotypes into a biallelic model by their supposed level of expression as follows: LG/SA/G, LG/LG, and SA/G/ SA/G were reclassified as S0S0 (lower expression), LA/SA/G and LA/LG