Before we dive into the benefits of exercise on mental health it is helpful to define what we consider to be positive mental health. The World Health Organisation (WHO) has defined positive mental health as “a state of well-being in which the individual realises his or her own abilities, can cope with the normal stresses of life, can work productively and fruitfully, and is able to make a contribution to his or her community.”
By this definition, positive mental health is a resource for well being, not just the absence of mental illness. Put simply, positive mental health encompasses feeling good and functioning well and includes aspects such as self esteem, optimism, self efficacy, satisfying personal relationships and resilience – the ability to cope with adversity and face stressors.
Research has proven that positive mental health is associated with reduced risk of mortality, better physical health, better academic achievement and social functioning and reduced risk of mental illness.
Mental illness is a diagnosable mental health condition that affects a person’s thinking, feeling, mood or behaviour. Our mental health reflects our emotional, psychological and social well-being. Affecting how we think, feel and act, mental health has a strong impact on the way we interact with others, handle problems and make decisions.
Many people with poor mental health have not been formally diagnosed with mental illness. People without mental illness can have periods during which they experience low mood and a decreased sense of well being. This does not mean that they have a mental illness. Conversely, people who have been diagnosed with mental illness can experience periods of physical, mental and social well being.
Mental health is a continuum from being asymptomatic and fully functional to having severe mental illness. Mental illnesses such as depression and anxiety lay on the continuum where symptoms are longer lasting and cause disability.
According to the Australian Institute of Health and Welfare 44% of Australians aged 16-85 are estimated to have experienced a mental disorder at some point in their life. Anxiety disorders are the most common affecting 17%, followed by Affective disorders such as depression (8%). In fact mental illness is the third largest source of disease burden in Australia after cancers and cardiovascular disease.
Depression is a mood disorder that causes a persistent feeling of sadness or hopelessness. Depression ranges from mild, temporary episodes of sadness to severe, persistent depression. Clinical Depression, also known as Major Depressive Disorder, is the most severe form of depression. A person with clinical depression needs special help to cope with day-to-day affairs.
Anxiety is a form of negative self appraisal characterised by worry, self doubt and apprehension. Everyone experiences anxiety from time to time. Having an anxiety disorder is not the same as feeling too anxious. The main features of an anxiety disorder are fears or thoughts that are chronic and distressing and that interfere with daily life.
Having clarified our understanding of mental health and mental illness let us investigate the link between exercise and mental health.
A meta-analysis of multiple studies investigating the correlation between physical activity and mental health strongly supports the link between regular physical activity and positive mental health. Conversely research has clearly established the association between physical inactivity and lower levels of positive mental health which potentially presents a risk for the development of mental illness.
It should be noted that, while some studies focus on the link between physical activity and mental health, others look more specifically at exercise. So, what is the difference? Physical activity is any movement a person does, including activities of daily living. Exercise is planned, structured, intentional movement, intended to improve or maintain physical fitness.
While physical activity has been proven to enhance mental health, exercise is the most beneficial, especially when considering the effectiveness for the alleviation of symptoms of depression and anxiety.
Research agrees that exercise does indeed have a positive influence on mental health. It is thought to:
While current evidence points to a consensus that exercise positively influences mental health there is less consensus on the mechanisms by which this is achieved, especially for conditions such as depression and anxiety. Further research is required before a definitive explanation can be provided. Studies conducted to date point to the synergistic influences of both neurobiological and behavioural mechanisms.
Exercise promotes physiological changes in the human brain via an increase in metabolism, oxygenation and blood flow in the brain. It is associated with increased synthesis and release of both neurotransmitters and neurotrophic factors which may be associated with the following processes:
Exercise has been found to modulate some of the major CNS neurotransmitters associated with alertness and well being. These include:
These neurotransmitters are released by the hippocampus. The hippocampus is intrinsic to regulating feedback of stress responses. This is impaired in those with depression and anxiety. Exercise has a particularly potent impact on hippocampus functioning. It is thought to enhance neurogenesis in the hippocampus, increasing synaptic plasticity and promoting hippocampal growth. These changes help to block or reverse the detrimental effects of chronic stress on the brain, which contributes to symptoms of depression and anxiety. This could be a key factor in its benefit for the management of symptoms of mental illness.
The neurotrophic growth factors enhanced by exercise and linked to neuroplasticity include modulation of brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF) and Insulin-like growth factor (IGF-1). These growth factors have systemic effects in regulating cellular bioenergetic function. This is disrupted in multiple mental health conditions including depression and anxiety, making it difficult to facilitate mood control.
Other neurochemicals released during exercise are endogenous opioids, produced by the pituitary glands and hypothalamus and endocannabinoids, produced and released in small quantities from a variety of tissues in the body, including the brain, muscle, fatty tissue and immune cells. Both endogenous opioids and endocannabinoids promote a sense of well being, decreased anxiety, sedation and decreased sensitivity to pain. The most well known of the endogenous opioids are endorphins. They are the body’s natural painkillers.
Endocannabinoids are also thought to have a role in hippocampus neurogenesis. An increase in endocannabinoid levels is typically associated with aerobic exercise, especially prolonged activity such as endurance running. It is this elevated level of endocannabinoids that is associated with the ‘runner’s high’, a state of euphoria and well being experienced after long bouts of exercise.
The final neurobiological mechanism to consider is the reduction of inflammation that results from exercise. Anxiety disorders, in particular, are associated with elevated levels of proinflammatory cytokine c-reactive protein (CRP) which cause chronic systemic inflammation. CRP is produced by the liver. Exercise has been proven to reduce CRP levels in the blood, which may reduce symptoms of anxiety related to the inflammatory state.
In addition to the direct neurobiological effects of exercise on the brain, it may also facilitate the learning of adaptive behavioural responses that improve mental health. These may be addressed as two categories – self-regulatory skills and cognitive control.
Exercise may improve an individual’s ability to cope with high levels of arousal. For example, high intensity exercise results in autonomic arousal that mimics anxiety (elevated heart rate and breathing rate). During exercise the person with an anxiety disorder experiences these sensations in a non-threatening context. This may increase their capacity to tolerate these interoceptive sensations.
Effective behavioural engagement, self-monitoring, cognitive flexibility, attention control and vigilance are all impaired in individuals with depression and anxiety. Behavioural change strategies associated with exercise, such as goal setting, activity planning, adaptive problem solving, provision of feedback and self-monitoring may improve cognitive control.
Realistic goal setting (SMART goals) and attainment can assist emotional regulation and increase self-mastery, self-efficacy and self concept. Exercise may also assist a person with mental illness by increasing their ability to direct and sustain attention to the present, decreasing rumination and excessive worry.
Having established that exercise enhances mental health and decreases symptoms of depression and anxiety, we need to determine the exercise prescription that optimises the benefits. Further research is required to definitively determine the type, frequency, duration and intensity of physical activity or exercise that delivers the best mental health benefits.
The truth is that the most effective exercise protocols for depression and anxiety have not yet been established, although it is becoming more widely accepted that exercise is a valid form of treatment for these conditions, either as a stand alone or an adjunct to more traditional treatments such as medication and psychotherapy such as cognitive behaviour therapy (CBT).
To date most studies have investigated the effects of aerobic exercise on mental health. Few have attempted to research the effects of resistance training and mind-body exercise. The small amount of evidence available does indicate a similar positive influence on mental health and reduction of symptoms of depression and anxiety.
There is little data available to guide the recommendation for the frequency, duration and intensity of exercise most beneficial for mental health, with discrepancies between studies. At present the recommended dose is the same as that recommended for general health by the Department of Health and The Heart Foundation of Australia – 150 minutes per week or 30 minutes, 5 times a week at a moderate-vigorous intensity (60 – 80 % HRMax).
It is thought that the greatest factor affecting the success of the use of exercise to enhance mental health is adherence. Although a single bout of exercise can enhance mood, reduce stress and increase feelings of well being, it is prolonged engagement in regular exercise that reaps the most benefit.
Exercise adherence poses a significant problem when advocating its use as a treatment strategy for mental illness, as drop out rates are high in this population. Given this fact, perhaps more important than any specific prescription, is ascertaining the frequency, duration, intensity and type of exercise that the person most enjoys. This may be the best approach to maximising adherence and the potential benefits of exercise.
It is important to note that many individuals with poor mental health or mental illness have lower starting levels of physical fitness. It is unclear as to whether baseline physical fitness influences the effect of exercise as a treatment for mental health disorders. Does physical fitness need to change for an exercise based intervention to be effective? Some evidence suggests that exercise is effective at reducing symptoms of depression and anxiety without a change in physical fitness. Other studies have found that the greatest improvements in symptoms are experienced by participants with lower starting levels of fitness and correlate with an increase of fitness. Is it possible that stand alone exercise interventions for mental illness may be best suited to populations with a low baseline level of fitness and that they may be less effective for those with higher fitness level? More research is required to answer these questions.
Given the neurobiological and behavioural mechanisms by which exercise enhances mental health and the known fact that the prevalence of mental illness is higher in individuals who are less physically active, it could be surmised that exercise, when engaged in regularly over an extended period of time, is preventative for mental illnesses such as depression and anxiety.
Could exercise be used as a primary preventative strategy for mental health conditions? It would certainly be a very cost effective, practical method of reducing the prevalence of depression, anxiety and other mental health disorders. Further research in non-clinical populations is required to support this hypothesis.
Although there is much scope for further research, the benefits of exercise on mental health are well established. While we are yet to fully understand the mechanisms by which exercise enhances mental health and alleviates symptoms of conditions such as depression and anxiety, we have enough evidence to advocate it as a viable form of intervention, if not as a stand alone treatment, certainly as an adjunctive treatment to traditional methods. Considering the prevalence of mental illness in Australia and the known link between positive mental health and physical activity, it is in the best interests of the non-clinical population to adhere to a regular exercise regime. If not preventative for mental illness, at the very least it will enhance stress resilience and promote a sense of well being, much needed in our modern society.
Disclaimer: Where Certificate III in Fitness, Cert III/Cert 3, or Fitness Coach is mentioned, it refers to SIS30321 Certificate III in Fitness. Where Certificate IV in Fitness, Cert IV/Cert 4, or Personal Trainer is mentioned, it refers to SIS40221 Certificate IV in Fitness. Where Master Trainer Program™ is mentioned, it refers to Fitness Essentials and SIS40221 Certificate IV in Fitness. Where Master Trainer Plus+ Program™ is mentioned, it refers to SIS30321 Certificate III in Fitness and SIS40221 Certificate IV in Fitness. Where Certificate IV in Massage or Cert IV/Cert 4 is mentioned, it refers to HLT42021 Certificate IV in Massage Therapy. Where Diploma of Remedial Massage is mentioned, it refers to HLT52021 Diploma of Remedial Massage.