Adolescence is marked by a significant increase in the incidence of risk for the onset of major depressive disorder (MDD) (Rohde et al, 2013). The detrimental and long reaching effects of MDD on adolescents’ mental and physical wellbeing, educational outcomes, and social lives have been well documented (Jaycox et al, 2009; Pettit et al, 2009). There is a clear need to explain the risk factors behind the onset of MDD in adolescence.
Research has shown that a particularly prominent risk factor is depression in a parent (Weissman, 2016). However, the developmental mechanisms or pathways that could be behind the link between parental depression and adolescent MDD have been less clearly defined.
New research recently published in JAMA Psychiatry, led by Dr Frances Rice (2017), has sought to explore whether possible developmental pathways could lie in the effects of parental depression on offspring emotional wellbeing, in terms of levels of anxiety, low mood, or irritability, which have all been found to be clinical antecedents or precursors of later mood disorder (Stringaris et al, 2009; Pine et al, 1999).
In a prospective longitudinal study of the biological offspring of parents with recurrent depression (defined in terms of experience of at least two episodes of MDD), 337 families were initially recruited to participate at baseline, primarily from general practices in the UK. The youngest child (aged 9-17) in each family was included in the study to minimise the likelihood that offspring had already experienced MDD.
Following their baseline assessments, parents and offspring were assessed at two follow-up time-points:
- Approximately 1 year after baseline (Time 2)
- Approximately 2 years after baseline (Time 3).
Follow-up data were collected for 279 families in total.
- Clinical antecedents: Offspring low mood and fear/anxiety were assessed using standardised self-report measures, and offspring irritability and disruptive behaviour were assessed using the Child and Adolescent Psychiatric Assessment (CAPA) (Angold et al, 2000), a semi-structured diagnostic interview
- Degree of familial risk: Severity of parental depression (defined in terms of hospitalisation or severity of associated impairment) and additional family history of depression (defined in terms of diagnoses of depression in first- and second-degree relatives of the child) were also assessed
- Social adversity: Drawing on the evidence highlighting the associations between recent experience of stressful life events and adolescent MDD (Goodyer et al, 1993), and economic disadvantage and adolescent MDD (McLaughlin et al, 2011), data on the number of recent stressful life events experienced by offspring and household income were also captured.
- Primary outcome: New-onset offspring MDD at either Time 2 or Time 3 was assessed using the CAPA and defined as the presence of at least five depressive symptoms, including low mood, irritability, or loss of interest in activities, and depression-related impairment
- Secondary outcome: The child’s mean total number of depressive symptoms, as derived from the CAPA, aggregated across Time 2 and Time 3.
Primary and secondary outcomes
- New-onset MDD (the primary outcome) was present in 20 (7.2%) adolescents (6 males and 14 females) at follow-up, with a mean age at onset of 14.4
- The mean number of depressive symptoms experienced by offspring at follow-up (the secondary outcome) was, on average, 1.85 (with a range of 0 to 8.5)
- The patterns of results (described below) were similar for both the primary and secondary outcomes.
- Both offspring irritability and fear/anxiety were independently and significantly associated with new-onset MDD in offspring
- The path from fear/anxiety to new-onset MDD was significantly stronger than the path from irritability
- In addition, the predictive effects of fear/anxiety on new-onset MDD in offspring appeared to be being driven by symptoms of generalised anxiety, and fear/anxiety also predicted a particularly early MDD onset
- Neither offspring disruptive behaviour nor low mood were significantly associated with new-onset MDD in offspring.
Degree of familial risk
- Both severity of parental depression and additional family history of depression were significantly associated with new-onset MDD in offspring
- However, neither of these indexes of familial risk were significantly associated with the clinical antecedents
- Moreover, upon examining the indirect effects of the familial risk indexes on new-onset MDD in offspring via the clinical antecedents (i.e. following the hypothesis, for example, that severity of parental depression could lead to adolescent MDD through its impact on levels of irritability in offspring), the authors found that none of the indirect effects were significant
- Both economic disadvantage and offspring experience of recent stressful life events were significantly associated with new-onset MDD in offspring
- In addition, both economic disadvantage and offspring experience of recent stressful life events were significantly associated with the clinical antecedents
- However, upon examining the indirect effects of the social adversity indexes on new-onset MDD in offspring via the clinical antecedents, the authors again found that none of the indirect effects were significant
Strengths and limitations
The strengths of this study include the important implications of its findings (discussed further below), which as Glowinski and Rosen (2017) outline in their commentary on Rice and colleagues’ article “will potentially pave the way for better prevention targets in high-risk youth” (p.160), its prospective longitudinal design that allowed the authors to explore the possible pathways to new-onset MDD in adolescents, and the high participant retention rate across timepoints.
The limitations of this study, as Rice and colleagues acknowledge, include the low (but comparable to previous research) rates of new-onset MDD in offspring, meaning that all analyses relating to the primary outcome were conducted with a very small sample (N = 20), the potential influence of the different ways of measuring constructs (such as the differing numbers of items used to measure fear/anxiety and irritability) on the results, and the uncertainty around the generalisability of the findings to samples composed of a larger number of depressed fathers, as depressed mothers made up the majority of the sample in this study. Furthermore, the fact that none of the indirect effects examined in this study were significant means that the question of what exactly the developmental pathways are from such risk factors as familial risk/social adversity to adolescent MDD, is still tantalisingly on the table. However, rather than being a limitation of this study as such, this is arguably an interesting finding in its own right.
Conclusions and implications
Overall, the findings of this study suggest that there are six different routes to adolescent MDD:
- Two via clinical antecedents
- Two via familial risk factors
- severity of parental depression
- additional family history of depression
- Two via social adversity
- economic disadvantage
- number of recent stressful life events.
The authors also highlight the surprising finding that offspring low mood did not predict new-onset MDD and speculate whether the typically earlier emergence of symptoms of anxiety, as compared to symptoms of low mood, could partially explain this.
Importantly, the findings of this study indicate that preventive approaches for adolescent MDD could usefully target:
- The offspring of parents with depression
- Adolescents with elevated levels of fear/anxiety or irritability
- Adolescents who have experienced greater numbers of recent stressful life events (and I wonder whether there was a tipping point in relation to this or whether the effects of some events may be more potent than others)
- Adolescents from a social context of economic disadvantage.
As Rice and colleagues emphasise:
Effective prevention of adolescent MDD is important given the potential for long-term beneficial effects on adult functioning (p.157).
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