BACKGROUND: Investigating genetic modulation of emotion processing may 
contribute to the understanding of heritable mechanisms of emotional disorders. 
The aim of the present study was to test the effects of 
catechol-O-methyltransferase (COMT) val158met and serotonin-transporter-linked 
promoter region (5-HTTLPR) polymorphisms on facial emotion processing in healthy 
individuals.
METHODS: Two hundred and seventy five (167 female) participants were asked to 
complete a computerized facial affect recognition task, which involved four 
experimental conditions, each containing one type of emotional face (fearful, 
angry, sad or happy) intermixed with neutral faces. Participants were asked to 
indicate whether the face displayed an emotion or was neutral. The 
COMT-val158met and 5-HTTLPR polymorphisms were genotyped.
RESULTS: Met homozygotes (COMT) showed a stronger bias to perceive neutral faces 
as expressions of anger, compared with val homozygotes. However, the 
S-homozygotes (5-HTTLPR) showed a reduced bias to perceive neutral faces as 
expressions of happiness, compared to L-homozygotes. No interaction between 
5-HTTLPR and COMT was found.
CONCLUSIONS: These results add to the knowledge of individual differences in 
social cognition that are modulated via serotonergic and dopaminergic systems. 
This potentially could contribute to the understanding of the mechanisms of 
susceptibility to emotional disorders.