This is an excerpt from Physical Activity Epidemiology-3rd Edition by Rodney K. Dishman,Gregory W. Heath,Michael D. Schmidt & I-Min Lee.
Magnitude of the Problem
Anxiety disorders are the most common mental illnesses in the United States, affecting about 23 million people (4% of women and 2% of men) each year. In 2016, anxiety disorders were the 7th most burdensome disease based on years lived with disability and ranked 14th in terms of disability-adjusted life years (U.S. Burden of Disease Collaborators 2018). As is the case with depression, young people tend to have more anxiety than do older people. People in the age group of 15 to 24 years experience episodes of anxiety about 40% more often than people 25 to 54 years old, regardless of race. Lifetime prevalence of anxiety disorders in the United States are specific phobia (15.6%); social phobia (anxiety) (10.7%); separation anxiety (6.7%, including children and adolescents); GAD (4.3%); panic disorder with or without agoraphobia (3.8%); agoraphobia with or without panic disorder (2.5%); obsessive-compulsive disorder (2.3%); and 22% for any DSM-5 anxiety disorder in the United States (Kessler et al. 2012). PTSD (5.7%) is no longer classified as an anxiety disorder according to the DSM-5 (Kessler et al. 2012).
Social phobia is the most common anxiety disorder, with reported prevalence rates of up to 18.7%. The onset of social phobia typically occurs in childhood or adolescence; and the clinical course, if it is left untreated, is usually chronic, unremitting, and associated with significant functional impairment. Social phobia exhibits a high degree of comorbidity with other psychiatric disorders, including mood disorders, anxiety disorders, and substance abuse or dependence. Few people with social phobia seek professional help despite the existence of beneficial treatment approaches (Van Ameringen et al. 2003).
One of the most commonly encountered anxiety disorders in the primary care setting, panic disorder is a chronic and debilitating illness. Patients with panic disorder have medically unexplained symptoms that lead to overutilization of health care services (Pollack et al. 2003). Panic disorder is often comorbid with agoraphobia and major depression, and patients may be at increased risk of cardiovascular disease and, possibly, suicide.
Generalized anxiety disorder is a common disorder with a lifetime prevalence of 4% to 7% in the general population. Onset of GAD symptoms usually occurs during an individual’s early 20s; however, high rates of GAD have also been seen in children and adolescents. The clinical course of GAD is often chronic, with 40% of patients reporting illness lasting more than five years. Generalized anxiety disorder is associated with pronounced functional impairment, resulting in decreased vocational function and reduced quality of life. Patients with GAD tend to be high users of outpatient medical care, which contributes significantly to health care costs (Allgulander et al. 2003).
Physical Activity and Anxiety: The Evidence
The 1996 U.S. surgeon general’s report on physical activity and health (U.S. Department of Health and Human Services 1996) concluded that regular physical activity reduces feelings of anxiety. The scientific advisory committee for the 2018 Physical Activity Guidelines for Americans concluded that the evidence to support that physical activity or exercise reduces symptoms in anxiety patients and adults without an anxiety disorder was strong, but there was insufficient evidence for a dose response or whether the effects of exercise occur among youths or were modified by age, sex, race or ethnicity, socioeconomic status, or weight status (Physical Activity Guidelines Advisory Committee 2018). No conclusions were offered about whether regular physical activity protects against the development of an anxiety disorder or elevated symptoms of anxiety, but a subsequent review of the evidence indicates this also to be the case (McDowell et al. 2019).
A systematic review of 24 prospective cohort studies including more than 80,000 people followed for an average of nearly five years concluded that customary physical activity protects against anxiety symptoms and disorder (McDowell et al. 2019). Outcomes of 13 studies could be quantified for meta-analysis, indicating a 13% reduction in odds of elevated anxiety symptoms in nine studies (OR = 0.87), 33% reduction in odds of any anxiety disorder in three studies (OR = 0.66), and 46% reduction in odds of generalized anxiety disorder in three studies (OR = 0.54). The authors noted, though, that the evidence had varying degrees of bias because of the quality of the measures of exposure and outcomes, inconsistent adjustment for confounders, representativeness of samples, and attrition during follow-up. A contemporary review of 11 cohorts reported a similar reduction of 25% in odds of elevated symptoms or diagnosis of an anxiety disorder, but the only statistically significant reduction in a specific disorder was for agoraphobia (Schuch et al. 2019).
In contrast to the work on physical activity and depression, fewer prospective epidemiologic studies have examined whether regular physical activity protects against developing an anxiety disorder, and fewer RCTs have tested whether an exercise program can reduce anxiety symptoms in people diagnosed with an anxiety disorder. In contrast, many studies have experimentally examined the effects of acute exercise on state anxiety or of chronic exercise on trait anxiety among people without anxiety disorders, or in patients with medical conditions other than anxiety who were enrolled in RCTs of exercise mainly to improve their primary medical condition or fitness level.