How common is mental illness?
Psychological illnesses are extraordinarily common. The most common forms are anxiety and depression. A European study of depression found prevalence rates varying from 2.5% in Santander to 17% in Liverpool, while a worldwide study found rates of up to 29.5%. Anxiety is almost as common, affecting as many as 16% of the population over a lifetime.
At least in part, all of this misery would be lessened if as a society we took more regular exercise.
And its impact?
The severity of anxiety varies from low level disquiet to a state of panic or permanent terror. Depression can progress from mild unhappiness to profound despair. In their worst forms these illnesses can be totally incapacitating and sometimes fatal. Depression is the main cause of suicide which is commonest among men aged 40 to 50. There are about 6,500 deaths by suicide annually in the UK and the rate is rising.
Mental health problems are associated with enormous direct costs for individuals and society, including the provision of health and social care, and indirect costs such as lost employment. They are the third most important cause of sick leave. They account for about 18 million days’ sick leave, or 12.7% of the total sick days taken each year in the UK. The UK GDP could be over £25 billion higher if it were not for the economic consequences of mental health problems both to individuals and to businesses.
Exercise in the prevention of psychological disease:
A number of studies have indicated that regular exercise can reduce the risk of future depression. In the Norwegian HUNT study, 34,000 people without either mental or physical illness were followed up for 11 years and their exercise habit was compared with the risk of developing psychological symptoms. Undertaking regular leisure-time exercise was associated with reduced incidence of future depression. The majority of this protective effect occurred at low levels of exercise and was observed regardless of intensity. The findings suggested that about 12% of future cases of depression could have been prevented if all participants had engaged in at least one hour of physical activity each week.
A number of well conducted studies have confirmed this definite, if modest, reduction in risk of depression in regular exercisers. A 2012 meta-analysis of the association between regular exercise and subsequent depression included some 30 studies. 25 of these confirmed the association with a reduction in depression of between 8 and 67% in those doing less than 150 mins/week exercise and 19 – 27% in those doing more than 150 mins. A survey of more than a million adults in the US found that people who said that they took exercise experienced more than 50% fewer days of poor mental health. The effect was greatest in those with diagnosed depression and the optimal exercise dose was 45 minutes three to five times weekly. Exercising more than three hours daily was not helpful.
As I have emphasised so often in the past, most studies of the effects of exercise are based on self-reported levels of physical activity. A more reliable measure of exercise taking is provided by measuring cardio-respiratory fitness (CRF). This may explain the better relationship found for fitness and risk of mental illness. One review compared the association between risk of common mental illness and physical fitness in 27 million person years of data. Compared with those with a high level of fitness, those with a low level had a 47% greater risk of mental health disorders and those with a moderate level had a 23% greater risk. The revue also found a dose-response relationship between CRF and the risk of common mental health disorders.
Exercise in the treatment of psychological disease:
There is a general belief that physical activity and exercise have positive effects on mood and anxiety and a great number of publications describe an association of physical activity with general well-being, improved mood and lessened anxiety. Some intervention studies describe an anxiolytic (lessening of anxiety) and antidepressive activity of exercise in healthy subjects and in patients with mental illness. Exercise training has its greatest effect in major depression and panic disorder and can be particularly helpful in those with drug resistant depression.. A Cochrane report found that exercise can be as effective as either psychological therapies or antidepressant drugs.
Medical use of exercise in mental illness:
Although the evidence for positive effects of exercise on depression and anxiety is growing, its clinical use is still at a very early stage.
However exercise as treatment for anxiety and depression is becoming more mainstream. The Royal College of Psychiatrists recommends regular exercise as part of the treatment of of these conditions. They explain some possible mechanisms for benefit:
- Exercise seems to have an effect on certain chemicals in the brain, like dopamine and serotonin. Brain cells use these chemicals to communicate with each other, so they affect your mood and thinking.
- Exercise can stimulate other chemicals in the brain called “brain derived neurotrophic factors”. These help new brain cells to grow and develop. Moderate exercise seems to work better than vigorous exercise.
- Exercise seems to reduce harmful changes in the brain caused by stress.
I have no doubt that, with the increasing use of “social prescribing”, exercise prescription will grow and grow.