Monday June 22 2015
Prolonged sitting is thought to slow the metabolism
“Being a couch potato is bad for your mental health,” the Mail Online reports. However, the evidence gathered by a new review is not as clear-cut as the headline would lead you to believe.
The review summarised the results of nine studies on the link between anxiety symptoms and sedentary behaviour, such as using a computer or watching TV.
Overall, five of the nine studies found a positive link – that as time spent sitting went up, so did the risk of anxiety symptoms.
However, the results of a review are only as reliable as the studies it includes, and in this case they weren’t very good. The majority of studies looked at sitting and anxiety at one time.
This can’t prove cause and effect, as we are faced with the classic “chicken and egg” dilemma: does sedentary behaviour cause anxiety symptoms, or are anxious people likely to spend more time sitting?
Importantly, we don’t know whether the studies took account of other factors that could be influencing the results, and most looked only at anxiety symptoms, not a diagnosis of anxiety.
Overall, this review doesn’t provide conclusive proof of a definitive link. The occasional boxset binge is probably not going to trigger general anxiety disorder by itself, but it is important to balance this out with regular exercise. Aside from the physical health benefits of exercise, it can also often reduce feelings of depression and anxiety.
Where did the story come from?
The study was carried out by researchers from the School of Exercise and Nutrition Sciences at Deakin University in Burwood, Australia. No sources of funding are reported and the authors declare no conflicts of interest.
The study was published in the peer-reviewed medical journal BioMed Central Public Health. BioMed Central (BMC) publishes all its articles on an open-access basis. This means you can read the original research for free online, or download the PDF.
In concluding that being a couch potato is bad for your mental health and can cause anxiety, the Mail does not consider the important limitations of the studies on which this review is based. This includes that they cannot prove causation, and the majority have not looked at diagnoses of mental health illnesses.
What kind of research was this?
This was a systematic review aiming to look at the links between sedentary behaviour and anxiety levels.
Sedentary behaviour encompasses activities that require limited or no body movement, such as sitting (e.g. for work, travel), and screen-based activities, such as computer use, computer gaming and watching TV.
The researchers discuss how time spent sedentary has been associated with worse health in adults, irrespective of whether people do the recommended level of physical activity. Research has linked it to various chronic diseases, such as cardiovascular disease, diabetes and cancer. Studies have also looked into links with depression, but have not looked into other mental health illnesses, such as anxiety. Therefore, the research team decided to explore the potential effect of sedentary behaviour on anxiety.
A systematic review is one of the best ways of identifying and summarising all the available research on a particular issue. However, the review findings are only as good as the quality of the evidence they include. If the evidence is shaky, the review findings may be similarly unreliable.
What did the research involve?
The researchers searched literature databases for studies published from 1990 to end-2014. They looked for studies reporting keywords such as mental health or anxiety linked to sedentary behaviour, or computer or TV viewing. Eligible studies could be observational, including cross-sectional studies or prospective cohorts, or experimental study designs. The study populations could be children or adult, provided they only had anxiety or anxiety symptoms and did not have chronic medical conditions that could be affecting mental health.
The researchers assessed quality of the included studies and extracted the relevant data.
A total of nine relevant studies were eligible for inclusion in the review, seven of which were cross-sectional studies and two had a prospective (follow-up) design.
The studies varied in their included populations, measures and assessments. Seven studies included adults and two included children. Study sample sizes ranged from 189 to 13,470. Two of the studies came from Australia, two from the Netherlands, and the remaining came individually from the UK, US, Spain, China and Singapore.
Seven of the studies assessed sedentary behaviour by self-reporting questionnaires, asking people questions such as how much time they spent sitting, watching TV or viewing a computer screen. One of the studies in children had used parent reporting of the time the child spent in front of a screen. Four of the studies had looked specifically at leisure viewing, one looked at occupational viewing, and the others measured total daily time spent sedentary.
Only one of the studies used an accelerometer to objectively measure sedentary time and activity. When looking at anxiety, only one of the studies actually used a diagnostic interview to look for the presence of an anxiety disorder; the others all looked at symptoms. One of the studies used parent reporting of their child’s emotional symptoms on the Strengths and Difficulties Question; the other studies all assessed self-reported anxiety symptoms on a range of questionnaires.
What were the basic results?
Of the nine included studies, five – four cross-sectional and one prospective – found a positive link between sedentary behaviour and risk of anxiety. The other prospective study found no link, and the remaining three cross-sectional studies found either no link or the opposite link.
The researchers considered that, overall, there was moderate evidence for a link between sedentary behaviour and anxiety risk. Moderate evidence was defined as consistent results in one high-quality study and at least one weak-quality study; or consistent results in two or more weak-quality studies.
Looking more specifically into the results, four of five studies examining sitting times had found positive links. Two of four studies had found positive links with screen time (TV, gaming or computer). Two of three studies had found positive links with TV viewing, and one of two with computer use.
How did the researchers interpret the results?
The researchers conclude: “Limited evidence is available on the association between sedentary behaviour and risk of anxiety. However, our findings suggest a positive association (i.e. anxiety risk increases as sedentary behaviour time increases) may exist (particularly between sitting time and risk of anxiety). Further high-quality longitudinal/interventional research is needed to confirm findings and determine the direction of these relationships.”
This systematic review suggests that the more time people are sedentary (not moving much), the higher the risk of anxiety symptoms.
It has strengths in its systematic review methods, searching the literature for studies published over 25 years that examined the association, and assessing the quality of these studies. However, the results are only as reliable as the studies it includes. There are also important limitations to consider:
- The majority of studies in this review – seven of nine – were cross sectional. This means they questioned sedentary time and anxiety symptoms at once. These studies can show associations, but they cannot prove cause and effect. It is possible that sedentary time caused the anxiety symptoms, but just as possible that anxiety symptoms could have led to more sedentary behaviour.
- The possibility of confounding is another important limitation – both in the cross-sectional studies and the cohorts. From the information in the review, we have no idea whether the studies have taken into account the range of other factors that could be influencing any links between sedentary behaviour and anxiety symptoms. This could include physical and mental health illnesses, lifestyle (including diet and physical activity), environment and life events.
- The studies varied in their study methods, but most of them relied on self-reporting questionnaires, both for sedentary time and for the assessment of anxiety symptoms. For assessments of sedentary time, this could be inaccurate. For anxiety symptoms, this means the person doesn’t necessarily have anxiety. It is important to note that only one of the nine studies actually diagnosed anxiety; the other studies were looking at symptoms of anxiety. Without being an actual diagnosis of anxiety, is not known how many symptoms there were, or whether it would have actually be having an influence on the person’s daily life and wellbeing.
- The variations across the nine studies, including differences in age, nationality and type of sedentary time examined, mean the review conclusions aren’t particularly reliable. As the researchers say, further high-quality evidence is needed to confirm the links.
Despite the limitations, it is known that taking regular exercise has many health benefits, so reducing the time you spend sitting at work, while travelling or at home is a good thing.
Read more about why sitting too much is bad for your health.