Age may affect response to antidepressants with serotonergic and noradrenergic actions

Multiple lines of evidence suggest continuity from adolescent to adult depression, but treatment response is different in the two groups. There is some consensus that noradrenergic drugs are ineffective in adolescent depression. The aim of this study was to see whether this poor response extended to young adults.

Patients from two randomised studies on prediction of antidepressant response were used. The subjects were divided into a youth sample (ages 18-24) and an older sample (ages 25 and over). The 6-week percentage response, based on HDRS scores, and the number of patients in remission (i.e., HDRS < or =7) at 6 weeks were compared in subjects who received a serotonergic (clomipramine (mean dose 145 mg) and fluoxetine (mean dose 27 mg)) or a noradrenergic (desipramine (mean dose 200 mg) and nortriptyline (mean dose 100 mg)) antidepressant.

There were no significant differences between the two studies, except for a small variation in baseline Hamilton scores. Young adults had a poorer response to noradrenergic antidepressants than they did to serotonergic antidepressants, whereas there was no differential response in the older age group. Young adults had a lower rate of remission on a noradrenergic antidepressant (38% noradrenergic versus 72% serotonergic) but there was no significant difference in remission rates in older adults (65% noradrenergic versus 57% serotonergic) or the sample as a whole (54% noradrenergic versus 62% serotonergic).

The age cut-off at 24 is somewhat arbitrary. One study was double-blind while the other was open. There was no placebo control.

While the response rate to noradrenergic antidepressants in young adults is lower, it is not clear whether this is comparable to adolescents. The reasons for a reduced response may be related to maturation of the noradrenergic system in the brain. Our results suggest that age may be one factor to consider when choosing antidepressants for patients.