A new review of research into anxiety disorders has reported that women and adults under the age of 35 are more likely to experience anxiety than other groups.

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The researchers found that women, young adults, and people with other medical conditions were most at risk for anxiety disorders.

In particular, the researchers state that women are almost twice as likely to be affected as men. This difference did not change over time.

The aim of the review was to understand the prevalence of anxiety disorders in both the general public as well as among specific groups of people.

"Anxiety disorders can make life extremely difficult for some people and it is important for our health services to understand how common they are and which groups of people are at greatest risk," explains first author Olivia Remes, of the University of Cambridge in the United Kingdom.

According to the Centers for Disease Control and Prevention (CDC), anxiety disorders are the most common type of mental disorders present in the general population. Examples of anxiety disorders include post-traumatic stress disorder, obsessive-compulsive disorder (OCD), and social anxiety disorder.

The CDC estimate that the lifetime prevalence of anxiety disorders is more than 15 percent.

Typical symptoms of anxiety disorders include increased worrying, tension, tiredness, and fear. These symptoms can prevent people from keeping to their everyday routines. The study authors report that the annual cost of these disorders to the United States is estimated to be $42.3 billion.

Many more scientific reviews have examined the effects of depression than the effects of anxiety, despite this impact on society. The new review, published in Brain and Behavior, aims to shed further light on this area of research.

The team, led by the University of Cambridge, examined the findings of 48 reviews of anxiety studies. These included reviews on the development of anxiety, anxiety in relation to addiction, and anxiety alongside other conditions such as cancer and heart disease.

The reviews also looked at anxiety in different settings - both clinical and in the community - and in different places across the globe.

Anxiety rates largely unchanged from 1990-2010

Around 4 in every 100 people overall were reported to experience anxiety. Rates of anxiety were highest in North America (8 in every 100) and lowest in East Asia (less than 3 in every 100). These proportions remained largely the same from 1990-2010.

The groups of people who were most affected by anxiety disorders were women, adults under the age of 35, and people with other health conditions.

Around 10.9 percent of adults with cardiovascular disease in Western countries also had generalized anxiety disorder. Elsewhere, around 32 percent of people with multiple sclerosis also had an anxiety disorder.

OCD was found to be most prevalent in pregnant women and in women who had recently given birth. While around 1 in 100 people in the general population had OCD, the rate was raised in those who had recently given birth and almost double in pregnant women.

"By collecting all these data together, we see that these disorders are common across all groups, but women and young people are disproportionately affected," Remes says. "Also, people who have a chronic health condition are at a particular risk, adding a double burden on their lives."

The authors acknowledge that while anxiety disorders is a growing area of interest, there are some limitations to existing research. In particular, marginalized groups were underrepresented in the reviews the researchers looked at.

While anxiety disorders are an important issue among people identifying as lesbian, gay, or bisexual (LGB), for example, only one of the 48 reviews looked at LGB groups.

Prof. Carol Brayne, Director of the Cambridge Institute of Public Health, expands on this problem:

"Even with a reasonably large number of studies of anxiety disorder, data about marginalized groups is hard to find, and these are people who are likely to be at an even greater risk than the general population."

"We hope that, by identifying these gaps, future research can be directed towards these groups and include greater understanding of how such evidence can help reduce individual and population burdens," she concludes.

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