Consistent with previous findings,(25
) we found higher Neuroticism to be a risk marker for incident major and minor depression, independent of demographic and health risk factors. Lower Conscientiousness also emerged as a significant risk marker. None of the other personality domains were, by themselves, related to incident major or minor depression.
By examining trait combinations, we found evidence that Extraversion, Openness, and Conscientiousness played a role in determining whether high Neuroticism was related to incident major depression: the gloomy pessimists (N+E−), overly emotional (N+E+), hypersensitive (N+O+), and undercontrolled (N+C−) were at greater risk than other participants. We also found that low Extraversion, low Openness, and low Agreeableness amplify the risk conferred by low Conscientiousness.
Whereas these and other trait combinations were prospectively associated with major depression, only three styles, the undercontrolled (N+C−), reluctant scholars (O−C−), and well-intentioned (A+C−), were associated with minor depression. These findings raise the possibility that personality styles may be less important in the etiology of minor depression, even while the individual domains of Neuroticism and Conscientiousness are just as central to minor as major depression.
Individuals with the combination of high Neuroticism and low Conscientiousness – the undercontrolled style – appear to be the most vulnerable to developing depression. Individuals characterized by the undercontrolled style often find it difficult to control their impulses(37
), even when they know their actions are incongruent with their long-term interests.(33
) In the present research, this dispositional difficulty with impulse control was associated with the development of both major and minor depression, perhaps because these individuals are particularly vulnerable to the deleterious effects of poor self-management of health concerns. Neuroticism has long been identified as a risk-factor for depression; low Conscientiousness may augment that risk, high Conscientiousness may mitigate it.
Our findings broaden the understanding of personality and depression in the elderly in several ways. First, in addition to the anticipated effect of Neuroticism, our findings highlight the role of low Conscientiousness in predicting incident depression among the frail elderly. Individuals low in Conscientiousness may be more challenged by needing to manage their own care, navigating the complexities of the health care delivery system, and achieving personal goals despite limitations.(53
) Second, our findings highlight the importance of considering styles or combinations of personality domains. The analysis of styles suggests that rather than high Conscientiousness being protective, low Conscientiousness confers risk for mood disorders in this sample. Moreover, this risk is not solely specific to combinations of low Conscientiousness with high Neuroticism, but is also seen in combination with high or low scores on Extraversion, Agreeableness, and Openness. The findings that both low and high levels of Extraversion confer risk for depression in this context is particularly noteworthy as prior research on the role of low Extraversion in depression have been conflicting.(26
) Too often it is erroneously assumed that either high or low levels of a trait are pathogenic. The analysis of personality styles is not based on this assumption. Instead, it is consistent with the idea that high and
low levels of traits can be pathogenic, and that all traits have adaptive and maladaptive consequences.(48
) Third, while Neuroticism is strongly related to depression risk, many individuals who are high in Neuroticism live depression-free lives even in extreme old age, as data from this sample attest. Our findings suggest the intriguing possibility that those who live depression-free despite high levels of Neuroticism possess particular traits that serve to protect them, such as average to high Conscientiousness.
These findings should be of interest to treatment-providers. It is the rare clinician who ignores patient personality in creating and sustaining patient relationships, formulating assessments, and planning prevention, treatment or service-delivery strategies. Rather, clinicians adopt nuanced and complex views of their patients. By introducing the idea of personality styles to geriatric psychiatry, we aim to avoid the Scylla of the standard one-trait emphasis on, for example, Neuroticism and the Charybdis of examining personality disorders with dubious validity and relevance to older adults.(55
) Moreover, an emphasis on styles points to different approaches to depression prevention and treatment in the elderly. Because low Conscientiousness by itself or in combination with other domains confers risk for incident depression over and above that posed by Neuroticism, strategies to enhance the ability of individuals to identify or maintain roles, hobbies, and routines may be particularly effective,(56
) as deficits in these goal-oriented behaviors are distinguishing features of patients low in Conscientiousness. Our findings point to the potential utility of personality styles in identifying patients who might benefit from a trial targeting the prevention of major depression. Such an approach should be the focus of future intervention research.
The analysis of styles also has practical utility in daily practice. In contrast to personality scientists, who are trained to think dimensionally, clinicians tend to think categorically. Style membership is a source of conceptual economy for the clinician, as it conveys information about two or more variables simultaneously.(57
The present study was not without limitations. First, while we reduced the number of significance tests for the styles analyses by focusing only on styles related to Neuroticism and Conscientiousness, we did not use a formal correction to control for Type I errors. We chose this approach because, in the presence of a large number of predictors, standard methods of correcting for Type I errors (e.g., the Bonferroni) overcorrect and lead to a preponderance of Type II errors. While Type I errors are serious in clinical intervention studies, as they can lead to the implementation of costly programs that may be ineffective, Type II errors are more serious when they impair capacity to identify at-risk individuals. Given the significant unmet need for services among the depressed elderly, statistical procedures that further obscure risk detection are highly questionable. To alleviate concerns about Type I errors, however, we did note which findings were significant at a more stringent p-value (p < .01) and focus discussion on findings that were theoretically meaningful. Second, the present sample was mostly white and unique in its advanced age, poor health, and lower educational achievement. Therefore, the present findings may not describe general characteristics of major and minor depression or apply to other populations. Third, the MINI-MDE has not been used to assess minor depression nor validated against measures of minor depression. As such, the results for minor depression should be interpreted more cautiously than those with respect to major depression. Finally, data on prior depressive episodes were unavailable.
In conclusion, the present research demonstrates that combinations of traits influence risk for depression in the frail elderly. Our findings suggest that assessment of all five personality domains could improve the quality of care in geriatric depression and underscore the need for prevention studies that target participants who are high in Neuroticism and low in Conscientiousness. To gain a better, more nuanced understanding of depression and to be able to better predict who is at risk for major or minor depression requires the assessment of the full FFM and other clinical measures. Studying how these factors work synergistically and examining predictors that are common to and unique to different mood disorders will enable us to understand the biopsychosocial causes of depression and help insure the psychological and perhaps even the physical well-being of the oldest members of our communities.