Evolutionary Lifestyle and Mental Health

Evolutionary Psychology
www.epjournal.net – 2008. 6(1): 67-76
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Original Article
Evolutionary Lifestyle and Mental Health
Christopher J. Heath, Department of Psychology, University of Memphis, Memphis, USA.
Jeffrey S. Berman, Department of Psychology, University of Memphis, Memphis, USA. Email:
jberman@memphis.edu (Corresponding author)
Abstract: Some have suggested that psychological distress may be lower if individuals
adopt a lifestyle more similar to our evolutionary past. In this study, we assessed
relationships between distress and six lifestyle elements (sleep, omega-3 consumption,
exercise, rumination, sunlight exposure, and socialization). A large sample (N = 495) of
college undergraduates reported levels of each lifestyle element and their distress on the
Beck Depression Inventory and Hopkins Symptom Checklist. Analysis revealed a positive
relationship for rumination and a curvilinear relationship for sleep. In contrast, none of the
other elements correlated reliably with distress. The findings raise the possibility that
relationships between these lifestyle elements and distress may not be critical for the range
of exposure typically experienced in a normal, nonclinical population.
Keywords: mental health, evolutionary psychology, health behavior, treatment, lifestyle.
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Introduction
Modern life differs in a number of respects from the physical and social
environment likely experienced by our Paleolithic ancestors. These differences between the
current environment and that of the past could affect our psychological well-being (e.g., see
Buss, 2000; Cosmides and Tooby, 1999; Eaton, Konner, and Shostak, 1988). Such
differences include efficient means of transportation, machinery that can replace physical
labor, a constant progression of technologies to improve communications, and numerous
other resources that afford a greater level of convenience and efficiency than found in the
premodern world. However, these societal and technological advances have concurrently
deprived modern man of exposure to various factors that were present in the evolutionary
past. Many of these factors may have served as natural facilitators of mental health.
For example, in the premodern environment early man would have likely had a
sleep pattern more attuned to natural circadian rhythms not influenced by artificial light
(e.g., Bower, 1999), foods with higher levels of omega-3 fatty acids (e.g., Eaton, Eaton,
Sinclair, Cordain, and Mann, 1998; Eaton and Konner, 1985), higher levels of physical
activity (e.g., Cordain, Gotshall, Eaton, and Eaton, 1998), less ruminative thought
processes (e.g., Hollan, 1992; Schieffelin, 1985), more time exposed to sunlight (e.g.,

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Evolutionary lifestyle and mental health

Deacon, 1999) and fewer periods of social isolation (e.g., Gat, 1999). Research, in fact, has
established that all these factors are related to mental health (e.g., for sleep, see Cukrowicz
et al., 2006; Fava, 2004; for intake of omega-3, see Hibbeln and Salem, 1995; Keller, 2002;
for physical activity, see Doyne et al, 1987; Dunn, Trivedi, Kampert, Clark, and Chambliss,
2005; Freemont and Craighead, 1987; for rumination, see Beck, Rush, Shaw, and Emery,
1979; Teasdale, 1983; for light exposure, see Golden et al., 2005; Kripke, 1998; for
socialization, see Cohen, 2004).
Such evidence suggests that mental health could be impaired when levels in modern
life of these six elements—sleep, omega-3, exercise, rumination, sunlight, and
socialization—differ from that found in the evolutionary past. Recently, Ilardi and
colleagues (Ilardi, Karwoski, Lehman, Stites, and Steidtmann, 2007) have argued that a
modern lifestyle no longer provides adequate amounts of these factors and proposed a
novel treatment for individuals suffering from depression. The therapy prompts individuals
to make lifestyle changes by adjusting the six factors in their lives, and preliminary
evidence suggests the success of this approach (Ilardi et al., 2007; Karwoski, 2006).
Although research has linked each of the six individual lifestyle elements with
mental health, their relationship with mental health has not yet been evaluated
simultaneously for the same individuals. The aim of the present research was to assess
claims about these elements by examining whether their levels are related to mental health
in the general population. Further, by including multiple elements, the research allowed an
assessment of the possible combined effect of the elements. In the study, a large sample of
college undergraduates were asked to report levels of the lifestyle elements as well as
perceived psychological distress. We then evaluated whether there were linear or
curvilinear effects for each element and whether any of the findings varied by age or sex.
Method
Participants
Participants were 495 college students recruited from undergraduate psychology
courses at a large university.1 Their mean age was 20.9 years (SD = 4.3, range = 17–55)
and 70% were female.
Procedure
Participants were recruited from undergraduate psychology courses.
Announcements informed students that at the beginning or end of their next scheduled
class, they would have the opportunity to participate in a self-report survey in exchange for
extra course credit. For those who wished to participate, the survey was administered at the
next class meeting or an alternative time for students who could not attend the class
administration.
Each participant first completed the Lifestyle Elements Scale, which asked them to
indicate daily amounts of the six lifestyle elements experienced for the last week. They
then indicated their level of distress by completing the Beck Depression Inventory and the
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Hopkins Symptom Checklist.
The sample included only those who completed at least 20 of the 21 items on the
Beck Depression Inventory, 55 of the 58 items on the Hopkins Symptom Checklist, and an
entry for at least one day for each of the lifestyle elements. Missing scores were handled by
estimating the missing value from the mean of the other items on the measure.
When responding to the daily entries on the Lifestyle Elements Scale, a few
participants entered a verbal designation instead of a number. Verbal responses for a small
amount such as “a little” were assigned a value one standard deviation below the mean for
that day, terms for a large amount such as “a lot” were given a value one standard deviation
above the mean, and a response of “all day” was scored as the maximum reported number
for the day.2
Measures
Beck Depression Inventory. The Beck Depression Inventory II (Beck, Steer, and
Brown, 1996) is a widely used self-report measure for depression that includes 21 items.
Each item is scored from 0 to 3 to reflect the presence and severity of a depressive
symptom, with higher scores indicating a greater severity of depression.
Hopkins Symptom Checklist. The 58-item version of the Hopkins Symptom
Checklist (Derogatis, Lipman, Rickels, Uhlenhuth, and Covi, 1974a, 1974b) is a self-report
measure of symptoms commonly reported by individuals seeking psychological help. Each
symptom item is scored on a 4-point scale, indicating that the symptom bothered them not
at all (1), a little (2), quite a bit (3), or extremely (4).
Lifestyle Elements Scale. The Lifestyle Elements Scale is a self-report questionnaire
developed for this research to assess the amount of sleep, omega-3, exercise, rumination,
sunlight, and socialization that individuals have over the course of a week. Respondents
first indicate their age and sex. Then, for each day of the week, they enter a numerical value
in response to the following six questions: (a) “How many hours did you sleep each
night?”; (b) “How many servings of the following did you consume: fresh fish, canned fish,
an omega-3, or fish oil dietary supplement (pills)?”; (c) “How many minutes of physical
exercise did you receive each day? (i.e. aerobics programs, weightlifting, jogging, lap
swimming, sports such as basketball, soccer, racquetball, or similar exercise activities)”;
(d) “How many minutes during the day did you find yourself thinking or worrying over any
particular issue(s) in a nonproductive manner? (i.e. stressing, ruminating, obsessing, etc.)”;
(e) “How many minutes did you spend directly exposed to sunlight? Please only consider
times you were directly outdoors (not in the car, not sitting in shade, etc.)”; (f) “How many
minutes each day did you spend socializing outside of class? (i.e. attending parties,
shopping with friends, going to movies with friends, attending study groups, etc.).”




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Table 1. Mean, Standard Deviation, and Range for Lifestyle Elements and
Measures of Psychological Distress.




Variable
M SD Range




Lifestyle elementsa
Sleep hrs
6.7
1.1
2.9–13.7
Omega-3 servings
0.3
0.7
0.0–11.6
Exercise hrs
0.4
0.6
0.0–5.3
Rumination hrs
0.6
1.0
0.0–12.0
Sunlight hrs
0.6
0.8
0.0–8.3
Socialization hrs
2.0
1.9
0.0–11.0
Psychological distress
BDIb
11.4 8.1 0.0–51.5
SCLc
1.6 0.4 1.0–3.3




Note. N = 495.
aPer day across 1 week. bTotal score on Beck Depression Inventory. cMean
item score on Hopkins Symptom Checklist.
Results
Table 1 displays the mean, standard deviation, and range for the lifestyle elements
and measures of psychological distress. As can be seen, participants reported relatively low
daily averages of each element: approximately seven hours of sleep; less than half a serving
of omega-3; one-half hour of exercise, rumination, and exposure to sunlight; and two hours
socializing.
Because the Beck Depression Inventory and symptom checklist were highly
correlated, r(493) = .80, p < .001, a primary measure of overall distress was created by
transforming depression inventory scores and symptom checklist scores into standard
scores and then averaging these standard scores. To normalize their distributions, values for
the lifestyle elements were transformed by the square root.
Table 2 displays correlations between the lifestyle elements and the measure of
overall distress, Beck Depression Inventory, and Hopkins Symptom Checklist. Only levels
of rumination related reliably with either the overall distress measure or the component
measures of the depression inventory and symptom checklist. Correlations for the other
five elements were all close to zero. Moreover, a regression analysis of all the elements
except for rumination failed to predict overall distress reliably, R2 = .01, F(5, 489) = 1.22, p
= .3. Given the size of the sample, any substantial relationship would likely have been
detected. In fact, power analysis indicates that a sample of this size has a 95% chance of
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detecting correlations greater than .16 at the .05 confidence level.
It is possible that moderate levels of some of the lifestyle elements are associated
with better mental health, whereas extreme levels are related to greater distress. We
therefore assessed this possibility of curvilinear effects. Analysis revealed a curvilinear
pattern for sleep, t(492) = 2.61, p = .009. Participants reporting moderate levels of sleep (5–
9 hours) had lower levels of distress (mean overall distress = 0.0, n = 468) than those with
sleep values outside this range (mean overall distress = 0.4, n = 27), t(493) = 2.71 p = .007.
There was no similarly strong evidence of a curvilinear pattern for the remaining five
elements (ps > .07).
Although the age of our college sample was fairly homogeneous, some older
students were involved. We therefore assessed whether participant age might moderate
relationships between the lifestyle elements and distress. These analyses failed to indicate
that the relationship of any of the elements with distress varied as a function of age (all
interaction ps > .1).

Table 2. Correlations of Lifestyle Elements with Overall Distress,
Beck Depression Inventory, and Hopkins Symptom Checklist.




Distress
measure




Elementa Overallb
BDI SCL




Sleep
-.06 -.08 -.03
Omega-3
.07 .06 .07
Exercise
-.04 -.06 -.02
Rumination
.40* .35* .40*
Sunlight
-.04 -.05 -.03
Socialization
-.06 -.08 -.04




Note. N = 495 (df = 493).
aAll elements except omega-3 are square root of hours per day.
Omega-3 is square root of servings per day. bOverall distress is
mean of standardized scores for BDI and SCL.
*p < .05.

The sex of participants affected the findings of two elements, rumination and
exposure to sunlight. Rumination was related to distress more strongly for males (r = .52, p
< .001) than for females (r = .34, p < .001), interaction partial r =.10, p = .02. Although the
relationship between exposure to sunlight and distress differed between males and females,
interaction partial r = .09, p = .05, neither the relationship for males (r = -.11, p = .2) nor
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for females (r = .08, p = .2) differed reliably from zero.
Discussion
Among participants in the study, time spent ruminating was the only one of the six
lifestyle elements to yield a simple linear relationship with psychological distress. This
finding is consistent with previous research regarding ruminative thought processes (e.g.,
Morrison and O’Conner, 2005; Nolen-Hoeksema, Morrow, and Fredrickson, 1993). In
contrast, levels of sleep, omega-3, exercise, exposure to sunlight, and socialization—either
individually or taken together—did not correlate reliably with the distress measures. The
failure to detect such correlations is especially striking given the substantial statistical
power of the analyses.
Further analysis did indicate that sleep was related to mental health, although in a
nonlinear fashion. There seemed to be an optimum range of sleep: Typical amounts were
associated with lower distress, whereas participants who slept either less or more than the
mid values reported greater distress. This result parallels evidence from other research
suggesting the advantages of an optimum sleep range (e.g., Kaneita et al., 1996).
Participants in the study reported relatively low levels for many of the lifestyle
elements and this may explain the lack of other relationships with distress. For example,
although research has established the effectiveness of light therapy for improving mood
(e.g., Golden et al., 2005), investigators have noted that the time individuals typically spend
exposed to sunlight is rather low—as was the case in the present sample—and the intensity
of natural sunlight is less than that provided in bright light therapy research (Espiritu et al.,
1994). Similarly, investigations that have linked omega-3 and exercise to psychological
distress involved much higher levels than observed in our sample (e.g., for omega-3, see
Nemets, Stahl, and Belmaker, 2002; Peet and Horrobin, 2002; Stoll et al., 1999; for
exercise, see Dunn et al., 2005).
Relationships between the lifestyle elements and distress may also have been
suppressed because of the way the elements were measured. For instance, research focusing
on the quality of social interactions has found that positive social experiences correlate with
better mental health (e.g., Cohen, 2004; Ezquiaga, Garcia, Pallares, and Bravo, 1999). In
this study, however, participants indicated only how much time they spent socializing, not
the quality of those interactions. Also, participants may have been inaccurate in their
reporting of the lifestyle elements. In particular, they may not have been sufficiently
knowledgeable about omega-3 or the amounts of omega-3 typically found in foods (e.g.,
Verbeke, Sioen, Pieniak, Van Camp, and De Henauw, 2005). Further, past research
measuring omega-3 has used biological measures such as blood levels (Edwards, Peet,
Shay, and Horrobin 1997). Measuring the elements using similar biological measures or
daily intake diaries may yield more accurate reports than retrospective recollections.
Nevertheless, if the links with mental health are robust, even a relatively crude self-report
measure of the lifestyle elements would be expected to reveal relationships between these
elements and distress.
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Because our goal was to examine the role of the lifestyle elements in the general
population, participants were drawn from a nonclinical sample. Not surprisingly, the degree
of psychological distress reported by participants in the study was relatively modest
compared to that observed in clinical populations (e.g., see Beck et al., 1996, chap. 3;
Derogatis et al., 1974b). Relationships between the lifestyle elements and distress may
simply not occur within the range of distress levels of a normal population.
We did not find that the pattern of relationships between the lifestyle elements and
distress varied as a function of age. However, this was a college-age sample in which there
were relatively few older participants. Therefore, any moderating effect of age may have
been difficult to detect.
Although rumination was related to distress for both males and females, our
analyses indicated that the relationship was stronger for males. It is unclear why this pattern
differs from other research, which has suggested a stronger relationship among females
(e.g., Nolen-Hoeksema, 1987; Nolen-Hoeksema, Larson, and Grayson 1999).
Because rumination had by far the strongest and most straightforward relationship
with distress, adding other lifestyle elements to traditional anti-rumination strategies may
be unnecessary. Dealing only with problematic thought processes might be as effective as a
therapy combining multiple elements. Of course, this treatment implication presupposes
that our observed correlation between rumination and distress stems from rumination
causing distress rather than the other way around.
Promoting a lifestyle more consistent with that of the evolutionary past seems a
plausible approach to enhancing mental health. In fact, researchers have recently
recommended to the general public just such lifestyle changes for alleviating psychological
distress (e.g., Klein, 2007). However, results from the present study suggest that
relationships between many of these lifestyle elements and distress may not be particularly
prominent within the range of values typically found in the general population. To be
effective in reducing psychological distress, an intervention may need to expose individuals
to these lifestyle elements at the higher levels more similar to those experienced by our
Paleolithic ancestors.
Notes
1 An additional 22 individuals were excluded from the analyses because their questionnaires were not fully
completed.
2 Only 21 individuals used a verbal response when completing the Lifestyle Elements Scale. The pattern of
correlations between the lifestyle elements and the measures of distress were comparable when these
participants were excluded.

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Acknowledgements: The research reported in this article formed the basis for a master’s
thesis (Heath, 2008) completed by the first author under the supervision of the second
author. The research was supported by a Centers of Excellence grant awarded to the
Department of Psychology at the University of Memphis by the state of Tennessee.
Received 9 December 2007; Revision submitted 11 January 2008; Accepted 11
January 2008
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