However, response to treatment may be predicted by
baseline frontal lobe blood flow, and presence of polymorphisms of the 5 - hydroxytryptamine (5 - HT)-1 a gene, the LL genotype of the serotonin transporter linked polymorphic region (5 - HTTLPR) gene, and Val / Val homozygotes of the brain - derived neurotrophic factor (BDNF) gene.