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What are the mechanisms of action in determining how exercise can benefit those with a mental health disorder? There are two paths of thought on this. According to (insert reference point), "Hypothesized mechanisms of action fall into two broad categories: physiological and psychological factors. Proposed physiological mediators of the relationship between exercise and mental health include changes in the metabolism and availability of central neurotransmitters (e.g., serotonin, endogenous opioids) and sleep regulation. Psychological mediational hypotheses that have received some empirical attention include changes in coping self-efficacy and the interruption of negative thoughts. In the next section, we discuss the preliminary findings pertaining to these hypotheses."(pg. 186) For the physiological theory, physical activity has been shown to increase the available amount of serotonin in the human brain. Support for their hypothesis comes from a neuroendocrine challenge study in which they compared marathon runners to sedentary controls on their responses to metachlorophenylpiperazine (m-CPP), a 5-HT agonist that produces anxiogenic symptoms via 5-HT2C receptors (Broocks et al., 1999). They found that, relative to sedentary participants, marathon runners showed a diminishedcortisol response to m-CPP. This reduction in cortisol response among exercising participants suggests a reduced hormonal reaction to m-CPP mediated by postsynaptic 5-HT2C receptors, thus suggesting that anxiolytic and antidepressant effects of exercise may be mediated by the down-regulation of 5-HT2C receptors. Based on the observation that physical activity causes a release of endogenous opioids (Morgan, 1985; Ransford, 1982), it has been hypothesized that the inhibitory effects of beta-endorphins on the central nervous system are in part responsible for antidepressant and anxiolytic effects of exercise (Thoren, Floras, Hoffman, & Seals, 1990). Indeed, several studies have shown that participants who engage in aerobic exercise are more likely to be calmer and less depressed than those participants who did not engage in exercise following administration of an opiate antagonist (Allen & Coen, 1987; Daniel, Martin, & Carter, 1992; Janal, Colt, Clark, & Glusman, 1984). Markoff, Ryan, and Young (1982), however, failed to find this effect. The question whether changes in central neurotransmitter function account for the therapeutic effects of exercise awaits further examination in clinical samples.

Cognitive Factors

Cognitive Factors Craft (2005) proposed that engaging in an exercise program may provide the mastery experiences needed to promote the perceived ability to cope with depression, and thereby, improve mood. Employing a quasi-experimental design, Craft (2005) found that women who exercised showed significantly higher coping self-efficacy and lower depression scores compared to nonexercising controls. An increase in perceived coping ability and a decrease in anxiety have also been observed in anxious individuals who initiated an exercise program (Steptoe, Edwards, Moses, & Mathews, 1989). Similarly, Bodin and Martinsen (2004) found that exercise that targeted self-efficacy (e.g., 45 min of martial arts) corresponded with significantly greater improvements in positive affect and state anxiety compared to exercise that did not target self-efficacy (e.g., 45 min of stationary bike exercise). Instead of directly increasing a sense of coping ability, physical exercise may alter the accessibility or intensity of ruminations, worries, and anxiety (Bahrke & Morgan, 1978; Leith, 1994). Craft (2005) found that exercise was associated with greater use of distraction techniques early in treatment and a decrease in rumination throughout the course of treatment. However, there was no significant association between distraction and depression in this study. A possible explanation for these results comes from a study by Goode and Roth (1993), who found that it is not distraction per se but the content of the distraction techniques in which people engage that is associated with changes in emotional well-being. More specifically, they reported that runners who focused on nonassociative thoughts (those not relating to exercising) showed less fatigue and, in some cases, decreases in tension and anxiety, compared to runners who focused on associative thoughts (monitoring the body and the exercise itself). The authors suggest that the effect could be described in terms of a stress-and-coping perspective, where physical activity improves mood because it evokes physiological release while allowing the mind to engage in anxiolytic thoughts (Goode & Roth, 1993). This hypothesis receives interesting but circumstantial support from recent neuropsychological studies. Affective disorders have been associated with hyperactivity in select prefrontal areas (Mayberg, 1997; Baxter et al., 1987), and several EEG studies provide evidence that exercise reduces prefrontal activation (for a review, see Kubitz & Pothakos, 1997). Also, Dietrich and Sparling (2004), using neuropsychological tests (the Wisconsin Card Sorting Task, the Brief Kaufman Intelligence Test, the Paced Auditory Serial Addition Task, and the Peabody Picture Vocabulary Test), recently demonstrated that during moderate exercise, prefrontal-dependent cognitive function becomes impaired while prefrontal-nondependent cognitive processes remain intact. Accordingly, one potential mechanism of the anxiolytic and antidepressant effects of exercise may be through the modification of prefrontal cognitive processes (Dietrich & Sparling, 2004), although this accounting does not yet take into account the complexity of frontal circuits (e.g., left versus right hemisphere activation, activation in the orbitofrontal versus dorsolatoral prefrontal contex) in relation to emotional regulation and mood disturbances (Siegle, Ghinassi, & Thase, in press)

{Stathopoulou, G., Powers, M. B., Berry, A. C., Smits, J. A., & Otto, M. W. (2006). Exercise interventions for mental health: a quantitative and qualitative review. Clinical Psychology: Science and Practice, 13(2), 179-193.}

North et al. (1990) reviewed the results of narrative and meta-analytic reviews investigating the effect of exercise on depression. In this review exercise is suggested to improve depression by changing people’s daily routine, increasing their interactions with others, helping them lose weight, participate in outdoor recreation and master difficult physical and psychological challenges. Evidence that biological factors may explain the beneficial effects of exercise on depression derives from research showing that exercise promotes the secretion of neurotransmitters like serotonin (Ransford 1982, Morgan 1985). Also, evidence from animal studies suggests exercise stimulates the secretion of endogenous morphines (‘Endorphins’) and produces a state of euphoria (Pert & Bowie 1979). The narrative reviews reviewed by North et al. (1990) provide evidence for the benefits of exercise on depression but these derived mainly from anecdotal observations. The meta-analytic review, however, supported the anecdotal observations. The effect of acute exercise (single exercise session) was different than for an exercise programme, but both were effective antidepressants. Exercise had a better effect on outcomes for respondents who were most physically and psychologically unhealthy at the outset of the studies. (478)

Petruzzello et al. (1991) conducted three meta-analyses to examine the effect of acute and chronic exercise on state (current) anxiety, trait (dispositional) anxiety and psychophysiological correlates of anxiety derived from published and unpublished studies (n = 104) reported between 1960 and 1989. The results for state anxiety showed that exercise produced a small effect on state anxiety (effect size = 0.24); the effect size was largest when the researchers used the Multiple Affect Adjective Checklist (MAACL) as the outcome measure of anxiety. Chronic exercise had a slightly better effect on anxiety than acute exercise. The effect of exercise was largest in pre–post test within-groups designs, aerobic exercise was better than anaerobic exercise, and high intensity exercise of 21–30 min duration had a better effect than low intensity exercise shorter than 20 min or longer than 30 min. The effect size was largest when anxiety was measured 20 min post-exercise. Effect sizes were largest in studies using matched controls and lowest in studies using random assignment. Effect sizes were largest in participants aged between 31 and 45. When trait anxiety was the outcome measure the effect size for exercise was moderate (0.34) overall. High intensity aerobic exercise of more than 40 min duration, performed for more than 15 weeks produced the highest effect sizes. Effect sizes were largest in participants aged below 18. For trait anxiety, exercise had the largest effect in people with a psychiatric illness. When psychophysiological correlates of anxiety were the outcome measures, exercise had a fairly large effect on anxiety (effect size = 0.56) overall. The effect size was largest when skin measures were used to measure anxiety. Acute exercise had a better effect on psychophysiological outcomes than chronic anxiety. Pre–post within-groups designs produced larger effect sizes than other designs. Lower intensity exercise, of up to 20 min duration, lasting 4–6 weeks produced the largest effect sizes. Effect sizes were largest in studies using matched controls, among 18 to 30-year-olds and those with a psychiatric illness (479)

There are several views that seek to explain the beneficial effects of exercise on anxiety. One view suggests that exercise raises body temperature and reduces muscle tension similar to the effect of having a warm bath – the socalled thermogenic hypothesis (Raglin & Morgan 1985). Another view suggests that exercise stimulates activity in the sympathetic nervous system (SNS); adrenaline levels are increased and this has an arousing effect. When the SNS is activated, it provides a catalyst for parasympathetic nervous system (PNS) activity; acetylcholine is released and this has a calming effect. This is known as the Opponents Process Model (Solomon 1980). Exercise is also thought to distract people from stressful events thereby reducing the anxiety provoking impact of these events (Bakre & Morgan 1978). It is unclear from the studies reviewed by North et al. (1990) how long term are the effects of exercise on anxiety. A recently published study addressed this issue.(479-480)

{Callaghan, P. (2004). Exercise: a neglected intervention in mental health care?. Journal of psychiatric and mental health nursing, 11(4), 476-483.}

). In terms of physical health, individuals with mental health disorders have the same physical health needs as the general population. Individuals with serious mental illness are more likely to be sedentary than the general population (Brown 1999; Chamove 1986; Davidson 2001) and are consequently at high risk for chronic medical conditions associated with inactivity. For example, much of the increase in chronic medical illness among individuals with serious mental illness may be attributed to the increased prevalence of obesity in this population (Goff 2005) and physical inactivity likely contributes to this increased prevalence. In terms of mental health, positive psychological effects from physical activity in clinical populations have been reported even among those individuals who experience no objective diagnostic improvement. Improved quality of life is particularly important for individuals with severe and enduring mental health problems when complete remission may be unrealistic (Faulkner 1999). For example, there is a potential role for exercise in the treatment of schizophrenia, Faulkner 2005 concludes that exercise may alleviate secondary symptoms of schizophrenia such as depression, low self-esteem and social withdrawal. (2)

At present, the plausible mechanisms for psychological change through physical activity and exercise fall into one of three broad perspectives: (1) biochemical changes such as increased levels of neurotransmitters (e.g. endorphins or serotonin), (2) physiological changes such as improved cardiovascular and muscle function, thermogenesis and, (3) psychological changes such as social support, sense of autonomy, improved perceptions of competence, enhanced body image, self-efficacy and distraction (Mutrie 2003) (3)

{Gorczynski, P., & Faulkner, G. (2010). Exercise therapy for schizophrenia. The Cochrane database of systematic reviews, (5), CD004412.}