Randomised controlled trials (RCTs) have provided considerable evidence for the short-term efficacy of cognitive behavioural therapy (CBT) in children and adolescents with depressive and anxiety disorders. However, the effectiveness and long-term stability of treatment effects under routine care conditions remain unproven.

This observational study investigates the effectiveness and stability of CBT under routine care conditions within a large sample of clinically referred youth with depressive and anxiety disorders.

Two hundred and twenty former patients (age 6–18 years at start of treatment) underwent a follow-up assessment (follow-up interval: M=5.3 years, SD=2.47). Parent and self-ratings of behavioural and emotional problems were obtained at the beginning and end of treatment and at follow-up. Additionally, at follow-up, a telephone interview and questionnaires exploring other mental symptoms and life satisfaction were administered.

A repeated measures ANOVA yielded statistically significant, medium to large pre– post symptom reductions (ηp 2=.15 to ηp²=.47) and small to medium post-follow-up symptom reductions (ηp²=.03 to ηp²=.19). At follow-up, between 57 and 70% of the sample reported a decrease in different emotional symptoms since the end of treatment, and 80% reported improved life satisfaction.

These findings provide evidence for the effectiveness and stability of treatment effects of CBT in youth with depressive and anxiety disorders under routine care conditions. Due to the lack of a direct control condition and a substantial proportion of missing data, the results must be interpreted with caution.