AWA: Academic Writing at Auckland

Introduction

The relationship between early adversity and the onset of depressive disorders has been well documented in the literature. In a seminal study, Kessler and Magee (1993) outlined several key themes, which have been repeatedly discussed in later articles. The definitions of both adversity and depression have been key, along with the dynamic relationship between stress and depression, the effect of socioeconomic status and gender, and the specificity of early adversity in relation to depression. All studies, however, have had major limitations, most notably, sample selection and the exclusion of some key dependent variables. With this in mind, there are still many options for future research, especially in regard to the specificity of the link between adversity and depression; the direction of the relationship and the exact mechanism of the link.

Definition and Measurement of Variables

In order to more clearly understand the relationship between early adversity and depression, the definitions of (and methods of measuring) these two variables should be considered. Any differences between studies in this respect may affect their comparability. Studies have considered “early adverse life events” and “early adversity” to mean cumulative stress, specific life events, or both during childhood or adolescence. Cumulative stress can be seen as chronic or consistently present circumstances which have a negative effect on the individual, or the accumulation of several stressful events (Turner & Butler, 2003). Examples of this in the literature have included lack of parental warmth or close friends in school (Ge, Lorenz, Conger, Elder, & Simons, 1994), criteria of family disadvantage such as marital disruption, physical illness, and socioeconomic hardship (Sadowski, Ugarte, Kolvin, Kaplan, & Barnes, 1999), and presence of alcoholism or mental illness in the family (Kessler & Magee, 1993).

In contrast, Uhrlass & Gibb (2007), assessed specific early adverse life events. This was defined as individual negative occurrences in childhood. Included were occurrences of emotional maltreatment such as humiliation, rejection, and extortion, as well as “negative life events” such as a death in the family. Much of the literature (Hammen, Henry, & Daley, 2000; Hazel, Hammen, Brennan, & Najman, 2008; Phillips, Hammen, Brennan, Najman, & Bor, 2005; Turner & Butler, 2003) did not contradistinguish these two types of early adversity, and investigated the effects of both on the development and onset of depression. A range of measurement tools were used for assessing adversity within the literature, most taking the form of a specially-written survey or interview. Others used pre-existing assessments such as the UCLA Life Stress Interview (Hazel et al., 2008), the Life Experiences Questionnaire, and the Hassles and Uplifts Scale (Uhrlass & Gibb, 2007).

Likewise, the independent variable has been approached from two directions. The first is the development of depression as a clinically diagnosed condition. Phillips et al. (2005) and Hazel et al. (2008) used the Schedule for Affective Disorders and Schizophrenia for School-age Children, revised for the DSM-IV (K-SADS-E) as criteria to determine the presence of current and past depression. Similarly, Sadowski et al. (1999), Hammen et al. (2000), Turner & Butler (2003), and Turner & Lloyd (2004) employed the use of standardised interviews based on the Diagnostic and Statistical Manual of Mental Disorders (DSM) to determine if participants had developed depression. In contrast, some studies used depressive symptoms as the independent variable. Uhrlass & Gibb (2007) used the Beck Depression Inventory to measure the presence of depressive symptoms and their severity, while Ge et al. (1994) used the Symptom Checklist 90 (Revised; SCL-90-R) to evaluate the presence of psychological distress and depressive symptoms. Kessler & Magee (1993) applied a liberal definition to life history of depression, and asked solely if the participants had experienced a time in their life, lasting over a week, where they felt depressed.

The Dynamic Relationship Between Adversity and Depression

There appears to be consensus amongst the studies that the presence of adversity in childhood affects the development of depression in adolescence and later life. Many of the studies expanded on this, and posit that the relationship between these two variables is not simple and unidirectional; rather, it is complex and dynamic. Uhrlass & Gibb (2007) explored the bidirectional relationship between the two variables, and determined that not only is exposure to adversity a risk factor for depression, but depression is also a determinant of vulnerability to further adversity. This positive feedback loop, also known as the stress generation model, has implications in the development of more severe depression or other disorders, and in the occurrence of depressive episodes. Similarly, Hazel et al. (2008) and Hammen et al. (2000) explored the effect of early adversity on stress sensitisation. These studies showed that the presence of early adversity may increase participants’ sensitivity to further stressors and adverse situations. In turn, this increases the total stress burden experienced by the individual, bringing them closer to their threshold for stress (Hammen et al., 2000). Once the threshold is reached, onset of depression (or a depressive episode) occurs - this interaction is known as the diathesis-stress model. This occurrence further increases the individual’s vulnerability to additional adversity by lowering their stress threshold (Kessler & Magee, 1993; Uhrlass & Gibb, 2007).

In contrast to this, some studies suggest a more linear causational pathway between early adversity and the development of depression, rather than one that feeds back upon itself. Ge et al. (1994), for example, posit that the inference from stressful events to depressed mood is stronger than the reverse. In other words, while adversity could be a key risk factor for developing depression, the presence of depression is not a risk factor for further exposure to adversity. Turner & Butler (2003) expand on this, demonstrating that the development of depression is linked to continuous exposure to stress, and that further exposure to stressors is more likely a continuation of early adversity than a product of a person’s history of depression.

The Effect of Socioeconomic Status and Gender

It is suggested in the literature that socioeconomic status and gender also play a role in determining the likelihood of childhood adversity occurring and the relationship this has with the onset of depressive disorders. While most argue that socioeconomic status has a large impact on whether a person will face early adversity, the link between these negative events and depression is widely debated, in this context. Turner and Butler (2003) suggest cumulative trauma is greater in children from lower socioeconomic backgrounds with this being directly linked to a higher prevalence of depression in these groups. Hazel et al. (2008) support this view, in their later study examining the role of recent stress on the link between early adversity and depression, suggesting that children from lower socioeconomic backgrounds often face continued stress and are at an increased risk for developing depressive disorders. It is a widely held view that this early adversity often faced by those living in lower socioeconomic areas, reduces stress tolerance, substantially increasing one's risk of depression in adulthood (Phillips et al., 2005). In contrast, Turner and Lloyd (2004), state that although lower socioeconomic status is clearly linked to an increase in childhood adverse events, there is no evidence to link this to an increase in depressive disorders, in this population. This study, on the lifetime occurrence of depression as a result of an early and major adverse event, may fail to examine the impact of cumulative stress faced by those living in lower socioeconomic conditions (Turner & Lloyd, 2004). It is therefore likely socioeconomic status plays a role in mediating the relationship between early adversity and the later development of depression.

To a lesser extent, the role of gender is also discussed in regard to early adversity as a predictor of depression. It is generally supported in the literature that females who have been exposed to risk factors are more likely to face future anxiety and depressive disorders, than young boys in the same groups (Phillips et al., 2005). However, girls who experience stable mothering and maternal love, support and warmth are less likely to later develop mental health disorders, this being one of the major risk factors (Ge et al., 1994). Ge et al. (1994), in their seminal study on the effect of parental warmth and stressful events on the later development of depressive symptoms, state this variable is much less of a predictor of future mental health issues in young boys. While girls are more likely to experience changes in mental health after puberty, boys are more likely to continue on the pattern of mental well-being established in childhood. Sadowski et al. (1999) add to this notion, suggesting females are especially vulnerable to having a later depressive episode if they have experienced poor parental care, in particular mothering, and poor physical care. From the current research, it is clear, young females are much more vulnerable to the effects of early adverse events.

Specificity of Early Adversity to Depressive Disorders

Although a clear link has been established between childhood adversity and depression and the mediating roles of socioeconomic status and gender, other mental illnesses have been largely neglected in the research. Current research suggests there could be just as much, if not more, of a link between childhood adversity and anxiety disorders (Phillips et al., 2005). It may be, early stress exposure is a greater risk factor for anxiety disorders and depressive disorders, while proximal stressors are the biggest risk factor for depressive disorders alone (Phillips et al., 2005). Recent results have indicated that adolescents facing anxiety disorders had been exposed to a greater number of early stressors including maternal partner changes and prenatal stress, than those adolescents facing depressive disorders (Phillips et al., 2005). With this in mind, it is important to note studies purely examining the relationship between early adversity and depression may have missed other key mental health outcomes; this is in fact, recognised as a limitation in numerous studies (Ge et al., 1994).

In addition, and as previously examined, it may be the relationship between early adversity and depression isn’t clear cut. Uhrlass and Gibb (2007) suggest childhood adversity mediates, rather than moderates later mental health disorders. By this, it is meant adversity can go on to cause issues such as a lack of social engagement, difficulties in forming attachment and the emergence of anti-social behaviour, as examples (Uhrlass & Gibb, 2007). These social difficulties, in turn, heighten one’s risk of then going on to develop a depressive disorder. In other words, adversity may be indirectly linked to depression, while more directly linked to adverse social outcomes (Uhrlass & Gibb, 2007).

From this, it could be summarised that although numerous studies have linked early adversity and depression, this relationship may also exist with other mental illnesses, or, in fact the relationship may be less direct than what has been previously stated.

Limitations to Current Research

A common limitation amongst several of the studies is the use of self-reporting to determine the presence of a depressive disorder or adverse life events. For the latter case, this can be an especially unreliable method, as the reported adversities can be heavily influenced by mood states (Uhrlass & Gibb, 2007). This can mean that those who are depressed may be more likely to respond negatively to measures than those who are not depressed. Similarly, the temporal order of events may be misremembered, thus affecting the validity of findings regarding causality (Turner & Lloyd, 2004).

Several of the studies also investigate a narrow age range. For example, Turner & Lloyd (2004) examine individuals 18-23 years of age, and the sample used by Hazel et al. (2008) consists of only 20-year-olds. This limits the studies in such a way that depression in later life (as a result of early adversity) cannot be studied.

The sample used by Ge et al. (1994) consists solely of white middle- to lower- class families living in rural areas; similarly, other studies (Uhrlass & Gibb, 2007; Turner & Lloyd, 2004; Hammen et al. 2000) select their samples based on small geographical areas, with little to no ethnic diversity. This makes it difficult to generalise the results to other populations, and leaves little room to investigate differences (or lack thereof) between ethnicities regarding the development of depression as a result of early adversity.

Suggestions for Future Research

There are three clear areas emerging from the current research that could be examined in the future. Firstly, and as already touched on, the link between early adversity and anxiety disorders, and the co-morbidity of anxiety and depressive disorders, in this context, should be examined further. To date, much of the existing research focuses on the specific link between adversity and depression, immediately ruling out the possibility of any other illnesses arising from early adversity (Phillips et al., 2005).

It has become clear, although some who face early adversity go on to develop depressive disorders, others do not (Turner & Lloyd, 2004). Although Ge et al. (1994) touch on one protective factor of parental warmth and support, a pertinent research topic would be to investigate what protective factors exist that mean some develop depression and others do not.

Finally, Hazel et al. (2008) suggest further research needs to be done into both the biological and psychosocial mechanisms by which traumatic stressors cause a later vulnerability to depression, allowing healthcare professionals to minimise a client’s risk.

Further research in these areas could potentially go on to produce favorable clinical outcomes in both the prevention and treatment of depressive disorders.

References

Ge, X., Lorenz, F. O., Conger, R. D., Elder, G. H., & Simons, R. L. (1994). Trajectories of stressful life events and depressive symptoms during adolescence. Developmental Psychology, 30(4), 467-483. doi:10.1037/0012-1649.30.4.467

Hammen, C., Henry, R., & Daley, S. E. (2000). Depression and sensitization to stressors among young women as a function of childhood adversity. Journal of Consulting and Clinical Psychology, 68(5), 782-787. doi:10.1037//0022-006X.68.5.782

Hazel, N. A., Hammen, C., Brennan, P. A., & Najma, J. (2008). Early childhood adversity and adolescent depression: The mediating role of continued stress. Psychological Medicine, 38(2), 581-589. doi:10.1017/S0033291708002857

Kessler, R. C., & Magee, W. J. (1993). Childhood adversities and adult depression: Basic patterns of association in a US national survey. Psychological Medicine, 23(3), 679-690. http://dx.doi.org.ezproxy.auckland.ac.nz/10.1017/S0033291700025460

Phillips, N. K., Hammen, C. L., Brennan, P. A., Najman, J. M., & Bor, W. (2005). Early adversity and the prospective prediction of depressive and anxiety disorders in adolescents. Journal of Abnormal Child Psychology, 33(1), 13-24. doi:10.1007/s10802-005-0930-3

Sadowski, H., Ugarte, B., Kolvin, I., Kaplan, C., & Barnes, J. (1999). Early life family disadvantages and major depression in adulthood. The British Journal of Psychiatry, 174(2), 112-120. doi:10.1192/bjp.174.2.112

Turner, H. A., & Butler, M. J. (2003). Direct and indirect effects of childhood adversity on depressive symptoms in young adults. Journal of Youth and Adolescence, 32(2), 89-103. Retrieved from http://link.springer.com.ezproxy.auckland.ac.nz/article/10.1023/A:1021 853600645

Turner, R. J., & Lloyd, D. A. (2004). Stress burden and the lifetime incidence of psychiatric disorder in young adults. Journal of the American Medical Association Psychiatry, 61(5), 481-488. doi:10.1001/archpsyc.61.5.481.

Uhrlass, D. J., & Gibb B. E. (2007). Childhood emotional maltreatment and the stress generation model of depression. Journal of Social and Clinical Psychology, 26(1), 119-130. doi:10.1521/jscp.2007.26.1.119