Scott, S.B., Whitehead, B.R., Bergeman, C.S., & Pitzer, L. (2013). Combinations of stressors in midlife: Examining role and domain stressors using regression trees and random forests. Journals of
Gerontology, Series B: Psychological Sciences and Social Sciences, 68(3), 464–475, doi:10.1093/geronb/gbs166. Advance Access publication January 22, 2013
© The Author 2013. Published by Oxford University Press on behalf of The Gerontological Society of America.
All rights reserved. For permissions, please e-mail: email@example.com.
Received September 23, 2011; Accepted December 19, 2012
Decision Editor: Merril Silverstein, PhD
Combinations of Stressors in Midlife: Examining Role
and Domain Stressors Using Regression Trees and
Stacey B. Scott,1 Brenda R. Whitehead,2 Cindy. S. Bergeman,2 and Lindsay Pitzer2
1Center for Healthy Aging, The Pennsylvania State University, University Park.
2Department of Psychology, University of Notre Dame, Indiana.
Lindsay Pitzer is now at Western Psychiatric Clinic and Institute at the University of Pittsburgh Medical Center.
Objectives. Global perceptions of stress (GPS) have major implications for mental and physical health, and stress
in midlife may influence adaptation in later life. Thus, it is important to determine the unique and interactive effects of
diverse influences of role stress (at work or in personal relationships), loneliness, life events, time pressure, caregiving,
finances, discrimination, and neighborhood circumstances on these GPS.
Method. Exploratory regression trees and random forests were used to examine complex interactions among myriad
events and chronic stressors in middle-aged participants’ (N = 410; mean age = 52.12) GPS.
Results. Different role and domain stressors were influential at high and low levels of loneliness. Varied combinations
of these stressors resulting in similar levels of perceived stress are also outlined as examples of equifinality. Loneliness
emerged as an important predictor across trees.
Discussion. Exploring multiple stressors simultaneously provides insights into the diversity of stressor combinations
across individuals—even those with similar levels of global perceived stress—and answers theoretical mandates to better
understand the influence of stress by sampling from many domain and role stressors. Further, the unique influences of
each predictor relative to the others inform theory and applied work. Finally, examples of equifinality and multifinality
call for targeted interventions.
Key Words: Loneliness—Random forests—Regression trees—Stress.
peting demands, including roles as workers, spouses, par-
ents, and adult children. They may experience precursors
to health problems (e.g., high cholesterol) or some of the
same conditions as their parents (e.g., diabetes). A range
of expected (e.g., retirement, children leaving home) and
unexpected (e.g., loss of spouse, being laid off) events may
occur during midlife. Aldwin and Levenson (2001) propose
that stress and coping processes in midlife contribute to the
individual differences in chronic health problems found in
middle age and later life. Stressful experiences in adulthood
may provide a context for development (Aldwin, 1994),
with challenging experiences in midlife serving as oppor-
tunities to adapt and hone emotion regulation skills for later
life periods (Magai & Halpern, 2001).
In the short term, however, the “fullness” of everyday life
during middle age, with its diverse roles, responsibilities,
and demands, may contribute to global perceptions of stress
(GPS). GPS reports reflect individuals’ feelings of overload,
uncontrollability, unpredictability, and distress about life.
As measured by the Perceived Stress Scale (PSS), this
IDDLE age is a period of marked diversity (Lachman,
2004). During midlife, individuals juggle many com-
instrument uses a 30-day recall period and is designed to
detect current levels of strain from ongoing chronic stressors,
impending events, and past events (Cohen, Kamarck, &
Mermelstein, 1983). GPS predicts a number of physical
and mental health outcomes including depressive symptoms
(Cohen et al., 1983), susceptibility to colds (Cohen, Tyrrell,
& Smith, 1993), changes in smoking rate (Cohen et al.,
1983), decreased gray matter volume in the hippocampus
(Gianaros et al., 2007), and telomere length and oxidative
stress as biological correlates of longevity (Epel et al., 2004).
Further, individuals who report high levels of GPS are more
affected by the experience of daily events (Stawski, Sliwinski,
Almeida, & Smyth, 2008; van Eck, Nicolson, & Berkhof,
1998). These ratings also change within persons across time;
in longitudinal studies, individuals are more responsive to
daily events during periods when they report higher levels
of GPS than during periods when they report lower GPS
(Sliwinski, Almeida, Smyth, & Stawski, 2009). Despite the
theoretical assumption that GPS serves to aggregate life
stress from multiple sources and evidence for it as a predictor
of a range of outcomes, little is known about the situations
that actually contribute to appraising life this way.
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The goal of this study is to identify combinations of
chronic stressors and life events that middle-aged persons
face and to explore how these relate to their overall per-
ceptions of current life stress. We have particular interest
in systems theory’s (Von Bertalanffy, 1969) concepts of
multifinality (i.e., shared stressor profiles resulting in differ-
ent levels of GPS) and equifinality (i.e., different combina-
tions of stressors related to similar levels of GPS). Evidence
for multifinality and equifinality has implications for both
stress theory and intervention.
Examining Multiple Stressors Together
Wheaton (1994) has described continua (Wheaton &
Montazer, 2010) over which components of the “stress
universe” can vary: discreteness (e.g., acute life events and
chronic stressors), macrolevel to microlevel, life course
(e.g., time at which stressor occurs relative to developmental
period), and severity. This orientation, as well as others’—
including notions of stress proliferation (Pearlin, Schieman,
Fazio, & Meersman, 2005) and life course perspective
(Aneshensel, 1992; Elder, George, & Shanahan, 1996;
Pearlin et al., 2005)—emphasizes that stress experiences
are contemporaneously and temporally contextualized. An
implication of this is that acute and chronic stressors are
experienced in concert with one another rather than indi-
vidually (Pearlin & Skaff, 1996; Wheaton, 1997); therefore,
it is unlikely that any one stressful experience is the sole
determinant of well-being. Indeed, Pearlin (1989, p. 241)
encouraged examining the “constellations of stressors made
up of both events and strains.” Researchers have responded,
documenting that middle-aged women balancing care for
relatives with AIDS with their other role commitments
(Wight, LeBlanc, & Aneshensel, 1998), bidirectional effects
between stress in work and family roles (Eckenrode & Gore,
1990), and the impact of individual traumas is attenuated by
prior stress histories (Wheaton, Roszell, & Hall, 1997).
According to the stress domain hypothesis (Wheaton,
1999), modest results found in past studies linking life
events to mental and physical health may be due to their
assessing a single source of stress that does not embody the
full effect of a stressor embedded in a social context. When
a variety of stress types (e.g., traumas, life events, chronic
stressors, and daily hassles) have been examined simulta-
neously, both unique and indirect effects on distress were
found (Wheaton & Montazer, 2010). Stress studies have
primarily been main effect focused (Wheaton & Montazer,
2010) or, in the case of the notable studies mentioned ear-
lier, limited in the number of predictors and interactions.
This was due, in part, to power constraints and analytic
techniques that limit the number of interactions that can be
examined. In this study, we employ regression trees (RT)
and random forests (RF) to build on the rich theory on the
various and mutually influencing stressors to document
how these diverse stressors relate to one other and influence
perceptions of stress. Subsequently, we overview chronic
stressors and life events from many domains particularly
relevant to midlife; then, we introduce an analytic approach,
relatively novel to stress research, to examine how complex
interactions between events and chronic stressors across
domains may be related to individuals’ subjective percep-
tions of life stress.
Chronic stressors include enduring problems, con-
flicts, and threats that people face in their everyday lives
(Cohen, Kessler, & Gordon, 1997; Turner, Wheaton, &
Lloyd, 1995); these stressors persist over time (Pearlin &
Skaff, 1996) and have been described as a continuous real-
ity or state (Wheaton, 1999). Role strains include ongoing
problems that arise from social roles, particularly family
relationships, whereas ambient strains pertain to problem-
atic facets of person–environment interactions (Pearlin &
Skaff, 1996). Highlighting the overlapping nature of stress-
ful experiences (Lepore, 1997), acute life events may be
particularly stressful when they lead to more chronic role
strains (Krause, 1994), such as job loss (Elder & Liker,
1982), divorce (Pearlin & Johnson, 1977), and widowhood
(Pearlin & Lieberman, 1979).
Role stressors.—Family, caregiving, romantic relation-
ships, and work. The consequences of recurring stressors
may be particularly severe when they surface within major
social domains, such as work or family (Pearlin, 1989;
Wheaton, 1994). Emergent role strains, such as caregiv-
ing, peak in midlife—one in five provides some degree
of caregiving (Brody, 1985; Marks, 1998)—and can be a
source of enduring stress. Moreover, events like children’s
departure, parents’ death, and retirement may exacerbate
strains produced by the multiple roles held during midlife
(Wethington, Kessler, & Pixley, 2004; Willis & Reid,
1999). Although some role combinations can lead to ben-
eficial effects on well-being (Moen, Dempster-McClain, &
Williams, 1989, 1992; Thoits, 1983; Vandewater, Ostrove,
& Stewart, 1997), occupying multiple roles may intro-
duce conflicting expectations leading to overload or con-
flict (Coverman, 1989). Because caregiving is often done
in combination with the potentially conflicting demands
of paid employment (Marks, 1998), women in the work-
place may find it difficult to satisfy their work requirements
along with the demands of caregiving for children and
frail parents (Aneshensel et al., 1995; Pearlin & Johnson,
1997). Apart from its conflict with other roles, work itself
is a significant source of stress in midlife, as adults in this
period are still likely to be involved in full-time employ-
ment, with many having reached positions involving con-
siderable management responsibilities and time demands.
Chronic stressors related to one’s job or career negatively
affect both short-term health indicators and long-term
STRESSORS IN MIDLIFE
by guest on January 2, 2016
Ormel, J., Lindenberg, S., Steverink, N., & Verbrugge, L. M. (1999).
Subjective well-being and social production functions. Social
Indicators Research, 46(1), 61–90.
Pearlin, L. I. (1989). The sociological study of stress. Journal of Health
and Social Behavior, 30(3), 241–256. doi:10.2307/2136956
Pearlin, L. I., Aneshensel, C. S., & Leblanc, A. J. (1997). The forms
and mechanisms of stress proliferation: The case of AIDS car-
egivers. Journal of Health and Social Behavior, 38(3), 223–236.
Pearlin, L. I., & Johnson, J. S. (1977). Marital status, life-strains and
depression. American Sociological Review, 42(5), 704–715.
Pearlin, L. I., & Lieberman, M. A. (1979). Social sources of emotional
distress. In R. Simmons (Ed.), Research in community and mental
health (Vol. 1, pp. 217–248). Greenwich, CT: JAI Press.
Pearlin, L. I., Menaghan, E. G., Morton A. Lieberman, & Mullan, J. T.
(1981). The stress process. Journal of Health and Social Behavior,
22(4), 337–356. doi:10.2307/2136676
Pearlin, L. I., Schieman, S., Fazio, E. M., & Meersman, S. C. (2005).
Stress, health, and the life course: Some conceptual perspec-
tives. Journal of Health and Social Behavior, 46(2), 205–219.
Pearlin, L. I., & Skaff, M. M. (1996). Stress and the life course: A paradig-
matic alliance. The Gerontologist, 36(2), 239.
Potter, P. T., & Zautra, A. J. (1997). Stressful life events’ effects on rheu-
matoid arthritis disease activity. Journal of Consulting and Clinical
Psychology, 65(2), 319–323. doi:10.1037/0022-006X.65.2.319
R Core Development Team. (2012). R: A language and environment for
statistical computing. Vienna, Austria: R Foundation for Statistical
Computing. Retrieved from http://www.R-project.org
Rook, K. S. (1984). Promoting social bonding: Strategies for helping the
lonely and socially isolated. American Psychologist, 39(12), 1389–
Russell, D., Peplau, L. A., & Cutrona, C. E. (1980). The revised UCLA
loneliness scale: Concurrent and discriminant validity evidence.
Journal of Personality and Social Psychology, 39(3), 472–480.
Ryff, C. D., Magee, W. J., Kling, K. C., & Wing, E. H. (1999). Forging
macro-micro linkages in the study of psychological well-being. In
The self and society in aging processes (pp. 247–278). New York,
Schlotz, W., Hellhammer, J., Schulz, P., & Stone, A. A. (2004). Perceived
work overload and chronic worrying predict weekend–weekday dif-
ferences in the cortisol awakening response. Psychosomatic Medicine,
66(2), 207–214. doi:10.1097/01.psy.0000116715.78238.56
Scott, S. B., Bergeman, C. S., Whitehead, B. R., & Pitzer, L. (in
press). Understanding global perceptions of stress in adulthood
through tree-based exploratory data mining. In J. J. McArdle & G.
Ritschard (Eds.), Contemporary issues in explorartory data min-
ing in the behavioral sciences. New York, NY: Taylor & Francis/
Scott, S. B., Jackson, B. R., & Bergeman, C. S. (2011). What contributes
to perceived stress in later life? A recursive partitioning approach.
Psychology and Aging, 26(4), 830–843. doi:10.1037/a0023180
Seeman, T. E., Berkman, L. F., Kohout, F., Lacroix, A., Glynn, R., &
Blazer, D. (1993). Intercommunity variations in the association
between social ties and mortality in the elderly: A comparative anal-
ysis of three communities. Annals of Epidemiology, 3(4), 325–335.
Seroczynski, A. D., Cole, D. A., & Maxwell, S. E. (1997). Cumulative and
compensatory effects of competence and incompetence on depres-
sive symptoms in children. Journal of Abnormal Psychology, 106(4),
Sliwinski, M. J., Almeida, D. M., Smyth, J., & Stawski, R. S. (2009).
Intraindividual change and variability in daily stress processes:
Findings from two measurement-burst diary studies. Psychology and
Aging, 24(4), 828–840. doi:10.1037/a0017925
Sroufe, L. A. (1997). Psychopathology as an outcome of development.
Development and Psychopathology, 9(02), 251–268. doi:10.1017/
Stawski, R. S., Sliwinski, M. J., Almeida, D. M., & Smyth, J. M. (2008).
Reported exposure and emotional reactivity to daily stressors: The
roles of adult age and global perceived stress. Psychology and Aging,
23(1), 52–61. doi:10.1037/0882-79126.96.36.199
Steinberg, D., & Colla, P. (1997). CART: Classification and regression
tress. San Diego, CA: Salford Systems.
Steverink, N., Veenstra, R., Oldehinkel, A., Gans, R., & Rosmalen, J.
(2011). Is social stress in the first half of life detrimental to later
physical and mental health in both men and women? European
Journal of Ageing, 8(1), 21–30. doi:10.1007/s10433-011-0178-4
Strobl, C., Boulesteix, A.-L., Kneib, T., Augustin, T., & Zeileis, A.
(2008). Conditional variable importance for random forests. BMC
Bioinformatics, 9(1), 307. doi:10.1186/1471-2105-9-307
Strobl, C., Boulesteix, A.-L., Zeileis, A., & Hothorn, T. (2007). Bias in ran-
dom forest variable importance measures: Illustrations, sources and a
solution. BMC Bioinformatics, 8(1), 25. doi:10.1186/1471-2105-8-25
Strobl, C., Hothorn, T., & Zeileis, A. (2009). Party on! A new, condi-
tional variable importance measure for random forests available in
the party package (Technical Report No. 050) (pp. 1–5). Munich:
Department of Statistics, University of Munich. Retrieved from
Strobl, C., Malley, J., & Tutz, G. (2009). An introduction to recursive par-
titioning: Rationale, application, and characteristics of classification
and regression trees, bagging, and random forests. Psychological
Methods, 14(4), 323–348. doi:10.1037/a0016973
Thoits, P. A. (1983). Multiple identities and psychological well-being:
A reformulation and test of the social isolation hypothesis. American
Sociological Review, 48(2), 174–187. doi:10.2307/2095103
Thoits, P. A. (1995). Stress, coping, and social support processes: Where
are we? What next? Journal of Health and Social Behavior, 35, 53–
Turner, R. J., Wheaton, B., & Lloyd, D. A. (1995). The epidemiology
of social stress. American Sociological Review, 60(1), 104–125.
Van Eck, M., Nicolson, N. A., & Berkhof, J. (1998). Effects of stressful
daily events on mood states: Relationship to global perceived stress.
Journal of Personality and Social Psychology, 75(6), 1572–1585.
Vandewater, E. A., Ostrove, J. M., & Stewart, A. J. (1997). Predicting wom-
en’s well-being in midlife: The importance of personality develop-
ment and social role involvements. Journal of Personality and Social
Psychology, 72(5), 1147–1160. doi:10.1037/0022-35188.8.131.527
Von Bertalanffy, L. (1969). General system theory: Foundations, develop-
ment, applications. New York, NY: G. Braziller.
Wallace, K. A., Bergeman, C. S., & Maxwell, S. E. (2002). Predicting
well-being outcomes in later life: An application of classification and
regression tree (CART) analysis. In Advances in psychology research
(Vol. 17, pp. 71–92). Hauppauge, NY: Nova Science.
Wethington, E., Kessler, R. C., & Pixley, J. E. (2004). Turning points in
adulthood. In O. G. Brim, C. D. Ryff, & R. C. Kessler (Eds.), How
Healthy Are We? A National Study of Well-being at Midlife (pp. 586–
613). Chicago, IL: University of Chicago Press.
Wheaton, B. (1994). Sampling the stress universe. In W. R. Avison (Ed.),
Stress and mental health: Contemporary issues and prospects for the
future (pp. 77–114). New York, NY: Plenum Press.
Wheaton, B. (1997). The nature of chronic stress. In B. H. Gottlieb (Ed.),
Coping with chronic stress (pp. 43–73). New York, NY: Plenum Press.
Wheaton, B. (1999). Social stress. In C. S. Aneshensel & J. C. Phelan
(Eds.), Handbook of the sociology of mental health (pp. 277–300).
New York, NY: Springer US.
Wheaton, B., & Montazer, S. (2010). Stressors, stress, and distress. In T.
L. Scheid (Ed.), A handbook for the study of mental health: Social
contexts, theories, and systems (2nd ed., pp. 171–199). New York,
NY: Cambridge University Press.
SCOTT ET AL.
by guest on January 2, 2016
Wheaton, B., Roszell, P., & Hall, K. (1997). The impact of twenty child-
hood and adult traumatic stressors on the risk of psychiatric disorder.
In I. H. Gotlib & B. Wheaton (Eds.), Stress and adversity over the
life course (pp. 50–72). New York, NY: Cambridge University Press.
Widmer, E. D., & Ritschard, G. (2009). The de-standardization
of the life course: Are men and women equal? Advances in
Life Course Research, 14(1–2), 28–39. doi:10.1016/j.alcr.
Wight, R. G., LeBlanc, A. J., & Aneshensel, C. S. (1998). AIDS caregiv-
ing and health among midlife and older women. Health Psychology,
17(2), 130–137. doi:10.1037/0278-6184.108.40.206
Williams, D. R., Yu, Y., Jackson, J. S., & Anderson, N. B. (1997). Racial
differences in physical and mental health socio-economic status,
stress and discrimination. Journal of Health Psychology, 2(3), 335–
Willis, S. L., & Reid, J. D. (1999). Life in the middle: psychological and
social development in middle age. San Diego, CA: Academic Press.
Yen, I. H., Michael, Y. L., & Perdue, L. (2009). Neighborhood environment
in studies of health of older adults. American Journal of Preventive
Medicine, 37(5), 455–463. doi:10.1016/j.amepre.2009.06.022
Zuckerman, M. (1999). Diathesis-stress models. In Vulnerability to psy-
chopathology: A biosocial model (pp. 3–23). Washington, DC:
American Psychological Association.
STRESSORS IN MIDLIFE
by guest on January 2, 2016