Mental health outcome of long-term and episodic adolescent depression: 15-year follow-up of a community sample

Abstract

Background

Recent studies have highlighted the unfavourable natural course of chronic/long-term depression. We investigated the adult mental health outcome of adolescent depression, with specific focus on long-term and episodic adolescent major depression (MD).

Methods

A community sample of depressed adolescents and non-depressed peers was followed-up with a structured diagnostic interview after 15 years. The participants (n = 382) were divided into five groups depending on their status in adolescence: no depression (n = 155); long-term MD (n = 91); episodic MD (n = 63); dysthymia (n = 33); and subthreshold symptoms (n = 40). Outcomes (age 19–31) included mood disorders, other mental disorders, suicidality, and treatment for mental disorders.

Results

The long-term group overall had a poorer outcome than the non-depressed group, with the episodic group in an intermediate position. The outcome of the dysthymic group was similar to that of the long-term group, while the subsyndromal group did not differ markedly from the non-depressed group. The long-term group was more likely than the episodic group to report adult anxiety disorders, multiple mental disorders, suicide attempts, and treatment; they also seemed to develop more persistent adult depressions, with a higher number of recurrent episodes and longer duration of antidepressant treatment. Even after adjustment for adolescent factors of clinical and etiological importance, the long-term group had a markedly less favourable outcome than the episodic group.

Limitation

The participation rate at follow-up was 64.6%.

Conclusion

Longstanding depression in adolescence is a powerful predictor of continued mental health problems in adulthood. It is now important to evaluate if early interventions can alter this severe course.

Introduction

It is widely documented that adolescent depression is associated with continued mental health problems in early adulthood. Both clinical and population-based studies have shown that depressed adolescents are more likely than their non-depressed peers to subsequently have depression, as well as non-mood disorders (Fergusson and Woodward, 2002, Harrington et al., 1990, Lewinsohn et al., 1999, Rao et al., 1995). In the Oregon Adolescent Depression Project, a large scale population-based follow-up of adolescent depression, 45% of the adolescents with MD reported at least one recurrent episode in early adulthood (age 19–24 years), while 33% reported a non-mood disorder and 62% reported any axis I diagnosis (Lewinsohn et al., 1999). Although this implies substantial continuity, it also illustrates that a large proportion of depressed adolescents appears to not have significant mental health problems in early adulthood—an impression that is reinforced by other follow-ups of clinical and population-based samples (Fergusson and Woodward, 2002, Harrington et al., 1990, Rao et al., 1995). This underlines the importance of identifying factors that can predict continued mental health problems following adolescent depression.

Recent studies have indicated that the persistence of adolescent depressive symptoms is predictive of subsequent mental health. A forty-year follow-up of the 1946 British birth cohort showed that adolescents with internalizing disorders at both age 13 and 15 were more likely than healthy adolescents to have adult mental disorders and to be treated for mental disorders in adulthood, while this was not the case for adolescents with an internalizing disorder at only one of these time-points (Colman et al., 2007). Similar results are reported from a study in which depressive symptoms were measured at three points in adolescence and young adulthood (Steinhausen et al., 2006). Episodic adolescent depression (high scores at only one of the time-points in adolescence) was not associated with abnormal psychosocial and mental functioning in early adulthood, while persistent high scores throughout the three time-points was. Further, results from the Oregon Adolescent Depression Project suggest that both number of depressive episodes and duration (defined as 9 weeks or more) predicts recurrence of depression in early adulthood (Lewinsohn et al., 2000).

In addition, studies on adult samples have highlighted the relevance of distinguishing between chronic and episodic forms of depression (Klein, 2008). Both clinical and population-based studies have shown that dysthymia and double depression (dysthymia with superimposed MD) in adults have a more protracted course and a higher risk of relapse than episodic MD (Klein et al., 2006, Rhebergen et al., 2009). Further, it has been reported that patients with chronic forms of depression have greater suicidality and receive more treatment (Klein et al., 2000). Comorbidity with non-mood disorders has also been reported to be more common in chronic forms of depression (Holm-Denoma et al., 2006, Rhebergen et al., 2009), as has somatic problems and role-impairment (Angst et al., 2009).

Thus, it seems that the duration of depression could have a major impact on the continued course. A long duration of depression in adolescence, a period of rapid mental development and acquisition of knowledge and social skills, might be particularly devastating to future mental health. However, covariates of long-term depression might also have an influence on the continued course; chronic forms of depression have been reported to differ from episodic depression on a number of clinically and etiologically important variables, such as family history of depression, high level of neuroticism, early adversities, and comorbid mental disorders (Angst et al., in press, Klein, 2008, Klein et al., 2009). In addition, the severity of a depressive episode has been reported to be predictive of recurrence and relapse (Klein, 2008).

A recent three-year follow-up of adults with dysthymia, double depression, and episodic MD, suggests that factors such as family history, childhood adversities, neuroticism, and comorbidity do not account for the difference in the natural course of chronic and non-chronic forms of depression (Rhebergen et al., 2009). To what extent this might be true also for adolescents has not yet been extensively studied. Investigation of the mental health outcome of adolescents with long-term MD and episodic MD, while taking potential confounders into account, could clarify this issue.

The general aim of this study was to investigate adult mental health outcome of adolescent depression. First, we intended to explore the outcome of subgroups of adolescent depression and non-depressed peers; we expected that longstanding adolescent depression in particular, both long-term MD and dysthymia, would predict a broad range of mental health problems in adulthood. Second, we hypothesized that the continued mental health problems would be more persistent, pervasive and severe in adolescents with long-term MD as compared to those with episodic MD. Third, we hypothesized that the difference in outcome between adolescents with long-term MD and episodic MD would remain after adjustment for clinically and etiologically relevant factors, such as severity of the adolescent depression, family-related adversities, trait anxiety, and comorbid mental disorders with an early onset.