Do noradrenaline and serotonin differentially affect social motivation and behaviour?

Abstract

In a placebo-controlled 8-week study comparing the selective noradrenaline re-uptake inhibitor (NARI), reboxetine, with the selective serotonin reuptake inhibitor (SSRI), fluoxetine, in major depression, patient social motivation and behaviour were investigated through a newly developed 21-item self-rating scale, the Social Adaptation Self-evaluation Scale (SASS). At last assessment the mean SASS total score was significantly superior on both reboxetine ( n = 103) and fluoxetine ( n = 100) compared with on placebo ( n = 99). In addition, the SASS total score in the reboxetine group was significantly higher compared with the fluoxetine group. At point–biserial correlation analysis, all but one item discriminated reboxetine from placebo, while only 12 items discriminated fluoxetine from placebo. In the reboxetine–fluoxetine comparison, nine items showed a positive association with reboxetine, while the opposite was never seen; the association was maximal in the area of negative self perception and lack of motivation towards action. These results support, at social functioning level, a differential effect of selective manipulation of the noradrenergic or serotonergic system in keeping with the long-debated hypothesis on the specific involvement of serotonin in regulating mood and of noradrenaline in sustaining drive.