Daniel M. Landers

ARIZONA STATE UNIVERSITY

ORIGINALLY PUBLISHED AS SERIES 2, NUMBER 12, OF THE PCPFS RESEARCH DIGEST
HIGHLIGHT

“We now have evidence to support the claim that exercise is related to positive
mental health as indicated by relief in symptoms of depression and anxiety.”

A NOTE FROM THE EDITORS

Mental health as discussed in this paper by Dr. Daniel Landers, a leading authority on this topic, 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.

Definitions

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 Both unpublished and published studies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 analysis.

Positive mood. Positive self-assessments associated with feelings of vigor, happiness, and/or other
positive feelings of well-being.

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 Activity

Reduced anxiety

• Best results with “aerobic exercise”
• Best after weeks of regular exercise
• Best benefits to those who are low fit to begin with
• Best benefits for those high in anxiety to begin with

Reduced depression

• 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 research)

Benefits (anxiety 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 health.

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., metaanalyses) 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 (Regier et al., 1988). In addition, stress-related
emotions, such as anxiety, are common among healthy individuals (Cohen, Tyrell, & Smith, 1991). 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 Lazarus and Cohen (1977), 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” (p. 109). 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 (Smith, 1989).

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 colorword test, active physical performance). The meta-analysis by Schlicht (1994), however, included some
stress-reactivity studies and therefore was not interpretable.

Landers and Petruzzello (1994) 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 normotensive adults.

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, strength-flexibility training), (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 (Kugler et al., 1994) and panic
disorder patients (Meyer, Broocks, Hillmer-Vogel, Bandelow, & Rüther, 1997). 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 (Kessler et al., 1994) and it is estimated that patients suffering from clinical depression make up 6–
8% of general medical practices (Katon & Schulberg, 1992). 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 (Simon, VonKorff, & Barlow, 1995). 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 (Hales & Travis, 1987; Martinsen, 1987, 1990).

The research on exercise and depression has a long history of investigators (Franz & Hamilton, 1905;
Vaux, 1926) 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 (Craft, 1997; North et al., 1990); (b) exercise was
of longer duration, higher intensity, and performed a greater number of days per week (Craft, 1997); and
(c) subjects were classified as medical rehabilitation patients (North et al., 1991) and, based on
questionnaire instruments, were classified as moderately/severely depressed compared to
mildly/moderately depressed (Craft, 1997). 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 (Gleser & Mendelberg, 1990; Martinsen, 1987,
1993, 1994), which indicate that exercise has antidepressant effects only for those who are initially mild
to moderately depressed.

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

Positive mood . 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.

Self-esteem . 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 selfconcept 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 perceptualmotor skills). Gruber (1986) also found that the effect of physical activity was larger for handicapped
compared to nonhandicapped children.

Restful sleep . 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 conservation
processes” (Kubitz et al., p. 278).

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).

SUMMARY

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 metaanalytic 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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