Going behind the headline news

Discussion

1. It was carried out by researchers based at the University of Cambridge and Westminster City Council, and funded by the UK National Institute for Health Research.

2. The study found that women, people under the age of 35, and those living with chronic physical conditions were disproportionately affected by anxiety disorders. Women were found to be almost twice as likely to be affected as men across different countries. However, the lack of representation from developing and under-developed parts of the world and the need for further study of the prevalence of anxiety in these parts of the world were pointed out by the researchers.

3. It was a systematic review (a synthesis of medical research evaluating relevant previously published studies, based on minimum ‘quality’ criteria for inclusion). The research aimed to collate evidence from previous studies looking at the prevalence of anxiety and global burden across subgroups within the population. Studies that were included varied widely in their methods and populations examined. Due to this variation, the researchers did not carry out a meta-analysis (a method that would have combined the results of individual studies), which would have provided a more robust analysis. They reported findings across individual studies instead.

4. Three literature databases, up to May 2015, were searched to identify previous systematic reviews and meta-analyses that had reported the burden of anxiety across the globe. The search covered all anxiety disorders including generalised anxiety disorder, social anxiety and obsessive-compulsive disorder, and methods used to assess anxiety. The researchers focused their search to look for reviews that included individuals suffering from other medical or mental health conditions (chronic or infectious disease, psychiatric conditions and addiction) as well as those from vulnerable populations. Reviews on the treatment of anxiety were excluded. Two researchers assessed the quality of the reviews and eligibility for inclusion, and extracted data. 48 studies were gathered to describe the global distribution of anxiety disorders. Selected reviews included studies of people of all ages, from young children to people of old age, with the overall number of studies and individual study sample sizes varying. Methods of assessment of anxiety varied between studies, from structured and unstructured interviews to self-reported questionnaires.

5. The prevalence of anxiety disorders within the population ranged from 3-25%. Women were found to be twice as likely to be affected as men (female:male ratio of 1.9 to 1). This was consistently the case across different countries and co-existing health conditions. Young adults under the age of 35 were also more often affected (2.5-9.1%). North America, North Africa and the Middle East were found to have the highest prevalence (7.7%, 6.8% and 7.7.% respectively), and East Asia had the lowest prevalence (2.8%) of anxiety disorders. The researchers found that prevalence was specifically higher in individuals who had chronic physical conditions such as cardiovascular disease, cancer, diabetes and respiratory diseases (1.4-70%).

6. They stated that important areas of research remained under-investigated or unexplored and although further studies on the prevalence of anxiety disorders were needed, the findings could serve to guide the research agenda and help develop timely interventions.

7. The study provides a general picture of the prevalence of anxiety disorders worldwide, but does not specify differences between types of anxiety disorder. Anxiety disorders were found to be common across all population groups, but women and young people seemed to be disproportionally affected. Although prevalence was higher in individuals with chronic conditions, there was no indication whether anxiety disorders were considered to be a contributing factor or a consequence of these conditions. The researchers highlighted the large variability in the methods of the reviews and the studies they included, which makes the comparison of prevalence figures between the studies difficult. There was wide variation between reviews in (i) number of studies they included and their sample sizes, (ii) the ages of participants, with some reviews focusing on adults and others on children, (iii) the population samples (general population samples or those with specific physical or mental health conditions), (iv) the assessment of anxiety, and (v) having accounted for confounding factors (i.e. whether the studies took account of other health, environmental or lifestyle factors that may have impacted on the outcomes being measured).

8. The review serves as a useful indicator of the prevalence of anxiety disorders, but cannot be taken to suggest causation. The higher prevalence in women or younger adults could be due to a complex interaction of biological, psychosocial and lifestyle factors. However, the direction of the effect or the extent of influence of different factors remains unknown. The researchers call for further studies to be carried out on the course of the illness, and note the need for research in developing and under-developed parts of the world, and for specific study into vulnerable subgroups of society.

9. No. The claim is based on opinion rather than evidence presented in the study. The Mail Online’s claim that the reason why younger women had higher levels of anxiety was down to being working mothers is not warranted (i.e. not supported by evidence) from the study.