Adolescent depression is a serious and debilitating disorder (see box). Up to one in 20 adolescents suffer from major depression at any point in time, and 20% of adolescents have at least one episode of clinical depression by the age of 18. Once depression is established it often becomes chronic. About a fifth of adolescents with major depression will continue to have a persistent disorder, and another third will recover but go on to have recurrent episodes.

CAUSATION

Depression runs in families and children of depressed parents have an increased risk of becoming depressed, which is likely to be due to both the direct effect of genes as well as the adverse influence of depressed parenting. Recent research has highlighted the complex interaction of genetic and environmental influences, such as adverse life events, in depression.

COMPLICATIONS

Pure depression is rare, and it is usually accompanied by other psychiatric disorders. A recent UK study found that 89% of cases had a comorbid disorder and the average number of additional disorders was three.1 Other complications include school refusal, academic failure, impaired peer relations, drug and alcohol abuse, and family relationship problems. However, the most important complication is suicide and depression is the most important risk factor for suicidality. Findings from 20-year follow-up data of depressed children and adolescents have shown that 2.5% had committed suicide and nearly half had attempted suicide.

Any treatment plan for adolescent depression therefore needs to take account of the chronic, relapsing nature of the disorder, consider aetiological factors such as parental depression, and address any concurrent psychiatric disorder and psychosocial complications, particularly suicidality.

EVIDENCE-BASED PSYCHOLOGICAL TREATMENT

Early studies of cognitive behavioural therapy (CBT) were promising in the prevention and treatment of depression and meta-analyses found large effect sizes. However, a recent meta-analysis, which included studies with active controls, reported a relatively small effect size of 0.3.2 The largest study, the Treatment of Adolescent Depression Study (TADS), which had more severely impaired participants than earlier studies, found that CBT alone did not differ from placebo on any of 15 outcomes.3 However, there is evidence from a sub-analysis that CBT may be effective in adolescents from higher income families4 and for high levels of cognitive disorders.

Recent findings in adult depression present an interesting line of evidence for the treatment of more severe depressive disorder. Dimidjian and colleagues reported that behavioural activation (using activity scheduling and graded tasks) without a cognitive component was comparable to antidepressant medication, and both significantly outperformed cognitive therapy.5 These results suggest that behavioural activation may be a useful treatment for more severe disorders and a viable alternative to antidepressant medication, although this needs to be tested in adolescents.

There have been three randomised controlled trials (RCTs) with positive results for interpersonal therapy (IPT). One trial was particularly encouraging as IPT was delivered by social workers with only basic training in therapeutic skills and proved to be superior to treatment as usual from school mental health teams.6 However, there are very few trained IPT therapists in the UK.

Although the role of parenting is thought to be important in both the genesis and maintenance of adolescent depression, the few studies of family intervention have generally yielded disappointing results. The addition of a parent group to CBT for depressed adolescents has not been shown to improve outcomes,7 and CBT significantly outperformed systemic family therapy in another study.8

EVIDENCE-BASED PHARMACOLOGICAL TREATMENT

There is little evidence that tricyclic antidepressants are efficacious in children and adolescents,9 and, in view of the side effects and risks of toxicity in overdose, they are not recommended in either UK or US guidelines.10 ,11

In recent years there has been much controversy surrounding the efficacy and safety of newer generation antidepressants (NGAs) in children and adolescents, in particular with regards to the issue of suicidality.

EVIDENCE BASE FOR COMBINED TREATMENT

TADS found a superior effect of fluoxetine combined with CBT when compared to either monotherapy (effect size 0.98 for depression scores);3 however, for more severe cases, there was no advantage of combined treatment over fluoxetine alone.4 The UK Adolescent Depression Antidepressant and Psychotherapy Trial (ADAPT),1 which had more severely depressed participants than TADS and higher levels of suicidality, failed to find an advantage of combined CBT and a selective serotonin reuptake inhibitor (SSRI) over an SSRI, in the context of usual care. Other studies have also not found an advantage of combined treatment over SSRIs.22 ,31 Results from TADS suggested that the addition of CBT to fluoxetine may reduce suicidality, although the ADAPT study failed to replicate this finding.1 Interestingly, ADAPT also reported that 20% of adolescents improved with a brief initial psychosocial intervention.

CONCLUSION

The evidence for CBT is conflicting, but it probably has a role in mild depression and for adolescents who refuse medication. There is some evidence to suggest that CBT may be more beneficial in high income families and for high levels of cognitive distortions. CBT is a scarce and expensive resource which therefore needs to be targeted at those who may benefit most. Interpersonal psychotherapy appears to be a promising treatment as is behavioural activation, but more training and research is needed in these areas. In moderate to severe depression, the greatest evidence for efficacy (compared with both placebo and CBT) has been demonstrated for fluoxetine. This should therefore be offered early in treatment, with an explanation of the evidence base and possible risk of suicidality with antidepressants, versus the known risk of suicide in depression, so families can make an informed decision regarding the possible risks and benefits of both medication and psychological treatment. However, ADAPT findings suggest that a non-specific brief psychosocial intervention may be helpful in some cases prior to initiating a more specialised treatment, and this requires further investigation. In light of recent evidence, the current UK NICE guidelines need revising.10 In the future we need improved trial methodology which reflects typical clinical populations, an improved understanding of phenomenology, and more effective targeted treatments, which take account of the heterogeneity found in adolescent depression.