Do children and adolescents have differential responsive rates in placebo-controlled trials of fluoxetine?

Objective: Recent acute efficacy trials of anti-depressants in youth have suggested that high placebo-response rates in children (<12 years of age) indicate that children may be more responsive to non-specific treatment interventions. Yet, these studies generally have not presented age-specific outcome data. The objective of this study was to compare the efficacy outcomes for children (<12 years of age) and adolescents (≥12 years of age) using the combined data from two previously published double-blind, placebo-controlled trials of fluoxetine. Methods: Children (<12 years of age) and adolescents (≥12 years of age) with major depressive disorder were randomized to fluoxetine or placebo for 8-9 weeks of treatment. Outcome was assessed using the Children's Depression Rating Scale-Revised (CDRS-R) and Clinical Global Impressions scale. Results: Random regression of the CDRS-R showed a treatment group by age group interaction (F_1,338=4.10, P=.044), indicating that the treatment effect was significantly more pronounced in children than adolescents. Within children, response at exit to fluoxetine was significantly better than placebo (56.9% vs 33.3%; P=.009). Adolescent response rates at exit were not significantly different between the groups (51.1% vs 38.6%; P=.128). Remission rates were low for both groups. Conclusion: In the combined fluoxetine trials, drug-placebo difference was greater in children compared with adolescents. Contrary to expectations, the placebo-response rate was lower in the children than the adolescents.