Dr. MJ Bazos MD,
Influence of Exercise on Mental Health
"We now have evidence to support the claim
that exercise is related to positive mental health as indicated by relief in
sympotoms of depression and anxiety."
Mental health as discussed in this
handout, focuses on conditions sometimes considered to be illness states (i.e.,
pathological depression) as well as conditions that limit wellness or quality of
life (i.e., anxiety, low self-esteem). To aid the reader, some basic terms used
in this paper are outlined in the boxes below.
Acute. Acute refers to something that
occurs at a specific time often for a relatively short duration. For example,
acute exercise refers to a bout of exercise done at a specific time for a
specific amount of time. Acute anxiety is anxiety that exists in a person in
response to a specific event (same as state anxiety).
Anxiety. Anxiety is a form of negative
self-appraisal characterized by worry, self-doubt, and apprehension.
Chronic. Chronic refers to something that
persists for a relatively long period of time. Chronic depression, for example,
would be depression that lasts a long time. A chronic exerciser is someone who
does exercise on a regular basis.
Depression. Depression is a state of
being associated with feelings of hopelessness or a sense of defeat. People with
depression often feel “down” or “blue” even when
circumstances would dictate otherwise. All people feel “depressed”
at times, but a “depressed” person feels this way much of the time.
Clinical depression. This is depression
(see definition) that persists for a relatively long period of time or becomes
so severe that a person needs special help to cope with day-to-day affairs.
Meta-analysis. A type of statistical
analysis that researchers use to make sense of many different research studies
done on the same topic. By analyzing findings from many different studies,
conclusions can be drawn concerning the results of all studies considered
together. Both unpublished and published studies can be included in this type of
Positive mood. Positive self-assessments
associated with feelings of vigor, happiness, and/or other positive feelings of
State anxiety. State anxiety is anxiety
present in very specific situations. For example, state sports anxiety is
present when a person is anxious in a specific sports situation even if the
person is not generally anxious.
Trait anxiety. Trait anxiety is the level
of anxiety present in a person on a regular basis. A person with high trait
anxiety is anxious much of the time while a person low in trait anxiety tends to
be anxious less often and in fewer situations.
Mental Health Benefits of Physical
- Best results with “aerobic
- Best after weeks of regular exercise
- Best benefits to those who are low fit to begin
- Best benefits for those high in anxiety to begin
- Best after weeks of regular exercise
- Best when done several times a week
- Best with more vigorous exercise
- Best for those who are more depressed (needs more
and depression) similar to those for other treatments
Activity associated with positive self-esteem
Activity associated with restful sleep
Activity associated with ability to respond to stress
For some time now, it has been common knowledge
that exercise is good for one’s physical health. It has only been in
recent years, however, that it has become commonplace to read in magazines and
health newsletters that exercise can also be of value in promoting sound mental
health. Although this optimistic appraisal has attracted a great deal of
attention, the scientific community has been much more cautious in offering such
a blanket endorsement. Consider the tentative conclusions from the Surgeon
General’s Report on Physical Activity and Health (PCPFS Research
Digest, 1996) that “physical activity appears to relieve symptoms of
depression and anxiety and improve mood” and that “regular physical
activity may reduce the risk of developing depression, although further research
is needed on this topic.”
The use of carefully chosen words, such as
“appears to” and “may” illustrate the caution that
people in the scientific community have when it comes to claiming mental health
benefits derived from exercise. Part of the problem in interpreting the
scientific literature is that there are over 100 scientific studies dealing with
exercise and depression or exercise and anxiety and not all of these studies
show statistically significant benefits with exercise training. The paucity of
clinical trial studies and the fact that a “mixed bag” of
significant and nonsignificant findings exists makes it difficult for scientists
to give a strong endorsement for the positive influence of exercise on mental
health. There is no doubt that the mental health area needs more clinical trial
studies. This would be particularly useful in determining if exercise
“causes” improvements in variables associated with sound mental
health. However, until these clinical trial studies materialize, there is still
much that can be done to strengthen statements made about exercise and mental
What evidence would prompt some scientists to
“stick their necks out” in favor of more definitive statements? One
reason for greater optimism is the recent appearance of quantitative reviews
(i.e., meta-analyses) of the literature on a number of mental health topics.
These reviews differ in several ways from the traditional narrative reviews. A
meta-analysis allows for a summary of results across studies. By including all
published and unpublished studies and combining their results, statistical power
is increased. Another advantage of using this type of review process is that a
clearly defined sequence of steps is followed and included in the final report
so that anyone can replicate the studies. Two additional advantages that
meta-analysis has over other types of reviews include: (a) the use of a
quantification technique that gives an objective estimate of the magnitude of
the exercise treatment effect; and (b) its ability to examine potential
moderating variables to determine if they influence exercise-mental health
relationships. Given these advantages, this paper will focus primarily on
results derived from large-scale meta-analytic reviews.
ANXIETY REDUCTION FOLLOWING EXERCISE
It is estimated that in the United States
approximately 7.3% of the adult population has an anxiety disorder that
necessitates some form of treatment. In addition, stress-related emotions, such
as anxiety, are common among healthy individuals. The current interest in
prevention has heightened interest in exercise as an alternative or adjunct to
traditional interventions such as psychotherapy or drug therapies.
Anxiety is associated with the emergence of a
negative form of cognitive appraisal typified by worry, self-doubt, and
apprehension. According to one study, it usually arises “...in the face of
demands that tax or exceed the resources of the system or ... demands to
which there are no readily available or automatic adaptive responses”.
Anxiety is a cognitive phenomenon and is usually measured by questionnaire
instruments. These questionnaires are sometimes accompanied by physiological
measures that are associated with heightened arousal/anxiety (e.g., heart rate,
blood pressure, skin conductance, muscle tension). A common distinction in this
literature is between state and trait questionnaire measures of anxiety. Trait
anxiety is the general predisposition to respond across many situations with
high levels of anxiety. State anxiety, on the other hand, is much more specific
and refers to the person’s anxiety at a particular moment. Although
“trait” and “state” aspects of anxiety are conceptually
distinct, the available operational measures show a considerable amount of
overlap among these subcomponents of anxiety.
For meta-analytic reviews of this topic, the
inclusion criterion has been that only studies examining anxiety measures before
and after either acute or chronic exercise have been included in the review.
Studies with experiment-imposed psychosocial stressors during the postexercise
period have not been included since this would confound the effects of exercise
with the effects of stressors (e.g., Stoop color-word test, active physical
performance). One meta-analysis, however, included some stress-reactivity
studies and therefore was not interpretable.
Another study examined the results of 27
narrative reviews that had been conducted between 1960 and 1991 and found that
in 81% of them the authors had concluded that physical activity/fitness was
related to anxiety reduction following exercise and there was little or no
conflicting data presented in these reviews. For the other 19%, the authors had
concluded that most of the findings were supportive of exercise being related to
a reduction in anxiety, but there were some divergent results. None of these
narrative reviews concluded that there was no relationship.
There have been six meta-analyses examining the
relationship between exercise and anxiety reduction (Calfas & Taylor, 1994;
Kugler, Seelback, & Krüskemper, 1994; Landers & Petruzzello, 1994;
Long & van Stavel, 1995; McDonald & Hodgdon, 1991; Petruzzello, Landers,
Hatfield, Kubitz, & Salazar, 1991). These meta-analyses ranged from 159
studies (Landers & Petruzzello, 1994; Petruzzello et al., 1991) to five
studies (Calfas & Taylor, 1994) reviewed. All six of these meta-analyses
found that across all studies examined, exercise was significantly related to a
reduction in anxiety. These effects ranged from “small” to
“moderate” in size and were consistent for trait, state, and
psychophysiological measures of anxiety. The vast majority of the narrative
reviews and all of the meta-analytic reviews support the conclusion that across
studies published between 1960 and 1995 there is a small to moderate
relationship showing that both acute and chronic exercise reduces anxiety. This
reduction occurs for all types of subjects, regardless of the measures of
anxiety being employed (i.e., state, trait or psychophysiological), the
intensity or the duration of the exercise, the type of exercise paradigm (i.e.,
acute or chronic), and the scientific quality of the studies. Another
meta-analysis (Kelley & Tran, 1995) of 35 clinical trial studies involving
1,076 subjects has confirmed the psychophysiological findings in showing small
(–4/–3 mm Hg), but statistically significant, postexercise
reductions for both systolic and diastolic blood pressure among normal
In addition to these general effects, some of
these meta-analyses (Landers & Petruzzello, 1994; Petruzzello et al., 1991)
that examined more studies and therefore had more findings to consider were able
to identify several variables that moderated the relationship between exercise
and anxiety reduction. Compared to the overall conclusion noted above, which is
based on hundreds of studies involving thousands of subjects, the findings for
the moderating variables are based on a much smaller database. More research,
therefore, is warranted to examine further the conclusions derived from the
following moderating variables.
The meta-analyses show that the larger
effects of exercise on anxiety reduction are shown when:
(a) the exercise is “aerobic” (e.g.,
running, swimming, cycling) as opposed to nonaerobic (e.g., handball,
(b) the length of the aerobic training program
is at least 10 weeks and preferably greater than 15 weeks, and
(c) subjects have initially lower levels of
fitness or higher levels of anxiety. The “higher levels of anxiety”
includes coronary and panic disorder patients.
In addition, there is limited evidence which
suggests that the anxiety reduction is not an artifact “due more to the
cessation of a potentially threatening activity than to the exercise
itself” (Petruzzello, 1995, p. 109), and the time course for postexercise
anxiety reduction is somewhere between four to six hours before anxiety returns
to pre-exercise levels (Landers & Petruzzello, 1994). It also appears that
although exercise differs from no treatment control groups, it is usually not
shown to differ from other known anxiety-reducing treatments (e.g., relaxation
training). The finding that exercise can produce an anxiety reduction similar in
magnitude to other commonly employed anxiety treatments is noteworthy since
exercise can be considered at least as good as these techniques, but in
addition, it has many other physical benefits.
EXERCISE AND DEPRESSION
Depression is a prevalent problem in
today’s society. Clinical depression affects 2–5% of Americans each
year and it is estimated that patients suffering from clinical depression make
up 6–8% of general medical practices. Depression is also costly to the
health care system in that depressed individuals annually spend 1.5 times more
on health care than nondepressed individuals, and those being treated with
antidepressants spend three times more on outpatient pharmacy costs than those
not on drug therapy. These costs have led to increased governmental pressure to
reduce health care costs in America. If available and effective, alternative
low-cost therapies that do not have negative side effects need to be
incorporated into treatment plans. Exercise has been proposed as an alternative
or adjunct to more traditional approaches for treating depression.
The research on exercise and depression has a
long history of investigators suggesting a relationship between exercise and
decreased depression. Since the early 1900s, there have been over 100 studies
examining this relationship, and many narrative reviews on this topic have also
been conducted. During the 1990s there have been at least five meta-analytic
reviews (Craft, 1997; Calfas & Taylor, 1994; Kugler et al., 1994; McDonald
& Hodgdon, 1991; North, McCullagh, & Tran, 1990) that have examined
studies ranging from as few as nine (Calfas & Taylor, 1994) to as many as 80
(North et al., 1990). Across these five meta-analytic reviews, the results
consistently show that both acute and chronic exercise are related to a
significant reduction in depression. These effects are generally
“moderate” in magnitude (i.e., larger than the anxiety-reducing
effects noted earlier) and occur for subjects who were classified as
nondepressed, clinically depressed, or mentally ill. The findings indicate that
the antidepressant effect of exercise begins as early as the first session of
exercise and persists beyond the end of the exercise program (Craft, 1997; North
et al., 1990). These effects are also consistent across age, gender, exercise
group size, and type of depression inventory.
Exercise was shown to produce larger
antidepressant effects when:
(a) the exercise training program was longer
than nine weeks and involved more sessions;
(b) exercise was of longer duration, higher
intensity, and performed a greater number of days per week; and
(c) subjects were classified as medical
rehabilitation patients and, based on questionnaire instruments, were classified
as moderately/severely depressed compared to mildly/moderately depressed.
The latter effect is limited since only one
study used individuals who were classified as severely depressed and only two
studies used individuals who were classified as moderately to severely
depressed. Although limited at this time, this finding calls into question the
conclusions of several narrative reviews, which indicate that exercise has
antidepressant effects only for those who are initially mild to moderately
The meta-analyses are inconsistent when
comparing exercise to the more traditional treatments for depression, such as
psychotherapy and behavioral interventions (e.g., relaxation, meditation), and
this may be related to the types of subjects employed. In examining all types of
subjects, North et al. (1990) found that exercise decreased depression more than
relaxation training or engaging in enjoyable activities, but did not produce
effects that were different from psychotherapy. Craft (1997), using only
clinically depressed subjects, found that exercise produced the same effects as
psychotherapy, behavioral interventions, and social contact. Exercise used in
combination with individual psychotherapy or exercise together with drug therapy
produced the largest effects; however, these effects were not significantly
different from the effect produced by exercise alone (Craft, 1997).
That exercise is at least as effective as more
traditional therapies is encouraging, especially considering the time and cost
involved with treatments like psychotherapy. Exercise may be a positive adjunct
for the treatment of depression since exercise provides additional health
benefits (e.g., increase in muscle tone and decreased incidence of heart disease
and obesity) that behavioral interventions do not. Thus, since exercise is cost
effective, has positive health benefits, and is effective in alleviating
depression, it is a viable adjunct or alternative to many of the more
traditional therapies. Future research also needs to examine the possibility of
systematically lowering antidepressant medication dosages while concurrently
supplementing treatment with exercise.
OTHER VARIABLES ASSOCIATED WITH MENTAL HEALTH
The Surgeon General’s Report also mentions
the possibility of exercise improving mood. Unfortunately the area of increased
positive mood as a result of acute and chronic exercise has only recently been
investigated and therefore there are no meta-analytic reviews in this area. Many
investigators are currently examining this subject and many of the preliminary
results have been encouraging. It remains to be seen if the additive effects of
these studies will result in conclusions that are as encouraging as the
relationship between exercise and the alleviation of negative mood states like
anxiety and depression.
Related to the area of positive mood states is
the area of physical activity and self-esteem. Although narrative reviews exist
in the area of physical activity and enhancement of self-esteem, there are
currently four meta-analytic reviews on this topic (Calfas & Taylor, 1994;
Gruber, 1986; McDonald & Hodgdon, 1991; Spence, Poon, & Dyck, 1997). The
number of studies in these meta-analyses ranged from 10 studies (Calfas &
Taylor, 1994) to 51 studies (Spence et al., 1997). All four of the reviews found
that physical activity/exercise brought about small, but statistically
significant, increases in physical self-concept or self-esteem. These effects
generalized across gender and age groups. In comparing self-esteem scores in
children, Gruber (1986) found that aerobic fitness produced much larger effects
on self-esteem scores than other types of physical education class activities
(e.g., learning sports skills or perceptual-motor skills). Gruber (1986) also
found that the effect of physical activity was larger for handicapped compared
to nonhandicapped children.
Another area associated with positive mental
health is the relationship between exercise and restful sleep. Two meta-analyses
have been conducted on this topic (Kubitz, Landers, Petruzzello, & Han,
1996; O’Connor & Youngstedt, 1995). The studies reviewed have
primarily examined sleep duration and total sleep time as well as measures
derived from electroencephalographic (EEG) activity while subjects are in
various stages of sleep. Operationally, sleep researchers have predicted that
sleep duration, total sleep time, and the amount of high amplitude, slow wave
EEG activity would be higher in physically fit individuals than those who are
unfit (i.e., chronic effect) and higher on nights following exercise (i.e.,
acute effect). This prediction is based on the “compensatory”
position, which posits that “fatiguing daytime activity (e.g., exercise)
would probably result in a compensatory increase in the need for and depth of
nighttime sleep, thereby facilitating recuperative, restorative and/or energy
The sleep meta-analyses by O’Connor and
Youngstedt (1995) and Kubitz et al. (1996) show support for this prediction.
Both reviews show that exercise significantly increases total sleep time and
aerobic exercise decreases rapid eye movement (REM) sleep. REM sleep is a
paradoxical form in that it is a deep sleep, but it is not as restful as slow
wave sleep (i.e., stages 3 and 4 sleep). Kubitz et al. (1996) found that acute
and chronic exercise was related to an increase in slow wave sleep and total
sleep time, but was also related to a decrease in sleep onset latency and REM
sleep. These findings support the compensatory position in that trained subjects
and those engaging in an acute bout of exercise went to sleep more quickly,
slept longer, and had a more restful sleep than untrained subjects or subjects
who did not exercise. There were moderating variables influencing these results.
Exercise had the biggest impact on sleep when: (a) the individuals were female,
low fit, or older; (b) the exercise was longer in duration; and (c) the exercise
was completed earlier in the day (Kubitz et al., 1996).
The research literature suggests that for many
variables there is now ample evidence that a definite relationship exists
between exercise and improved mental health. This is particularly evident in the
case of a reduction of anxiety and depression. For these topics, there is now
considerable evidence derived from over hundreds of studies with thousands of
subjects to support the claim that “exercise is related to a relief in
symptoms of depression and anxiety.” Obviously, more research is needed to
determine if this overall relationship is “causal,” and there is
also a need to examine further some of the variables that are believed to
moderate the overall relationship.
For many of the other variables related to
mental health, the initial meta-analyses have shown evidence that is promising.
Compared to the area of depression and anxiety, however, there is either a need
for more research on these topics or more quantitative reviews of the expansive
research that already exists. For example, the relatively new research into the
influence of exercise on positive mood states is in need of more research
studies, whereas the area of exercise and self-esteem needs quantitative reviews
of the expansive research literature that already exists. At the present time,
it appears that aerobic exercise enhances physical self-concept and self-esteem,
but more research needs to be done to confirm these initial findings. Exercise
is related not only to a relief in symptoms of depression and anxiety but it
also seems to be beneficial in enhancing self-esteem, producing more restful
sleep, and helping people recover more quickly from psychosocial stressors. None
of these relationships is the result of a single study. They are based on most,
if not all, of the available research in the English language at the time the
meta-analytic review was published. The overall positive patterns of the
meta-analytic findings for these variables lends greater confidence that
exercise has an important role to play in promoting sound mental health.
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