One possible explanation to this similarity of SSRIs and an SNRI, respectively, could be that the influence of duloxetine on NET in the human brain at the dosage used to treat depression may be lower than usually assumed; recent positron emission tomography studies thus indicate that duloxetine at clinically relevant dosage blocks less than 40% of NET but around 80% of the serotonin transporter (SERT) [39]. Here, SLC6A4 is linked to depressive symptom measurement.