It is quite well established that excessive (over 8 hours), particularly uninterrupted, sedentary behaviour (basically sitting) is associated with a range of adverse physical health conditions. But what about the impact of sedentary behaviour on the mind?
We and several other research groups have looked at this over the last few years and the results and actions we can take are important.
What does the research show?
1. Excessive sedentary behaviour appears to be slightly associated with an increased risk of depression
This meta-analysis found that overall sedentary behaviour is associated with ~25% increased risk of depression over time. This finding has been implicated in a number of other observational studies, but we really need additional data to see if this correlation is a potential “causative” factor. So we have an indication that there is a potential relationship.
2. “Enforcing” sedentary behaviour on healthy exercisers in trials increases stress and lowers mood
What adds some strength to the observational data is that there are several trials, which are needed to deduce causation, that have built upon this observational data.
In this first study, a group of 39 young students in their 20’s who were all healthy, regular exercisers, were randomly grouped to be more sedentary (cease all exercise and reduce their steps below 5000) whilst the other (control) group carried on as usual (i.e. exercising and being active). What they found is that after just one week, the group that engaged in sedentary behaviour had mood decreases (i.e. became more depressed on the PHQ scale) whereas unsurprisingly the control group mental health remained good. Thankfully the “intervention” only lasted one week and when the sedentary group were allowed to exercise again their mental health quickly improved back to baseline levels.
In a second randomised trial, a group in the UK showed that enforcing sedentary behaviour on healthy people in their 20’s over two weeks resulted in the young people becoming more stressed. But what was interesting was they were able to elucidate some of the underlying neurobiological reasons for this relationship. Specifically they found that there was an increase in the inflammatory cytokine interleukin-6 (IL-6) and we and others have shown that depression is associated with peripheral inflammation.
3. We have a huge problem in young people (but there is hope).
Among our other recent work, I am particularly concerned about the data in young people. In the recent paper in the Lancet, we measured physical activity and sedentary behaviour levels in over 4,200 children using accelerometers at age 12, 14 and 16. What we found, illustrated below, is really concerning.
Essentially, the only measure going up over time is Sedentary behaviour (in blue) which is not good. The levels of moderate and vigorous physical activity were virtually non-existent, and the level of light physical activity declined sharply as the children got older (in red).
Perhaps unsurprisingly, we showed that the children who were persistently engaged in high sedentary behaviour were more likely to have depression in the future. But, there is some hope and a call to action. We were able to demonstrate that if the children could replace one hour of sedentary behaviour time with activity, we could potentially reduce new cases of depression by approximately 10%. We know that the burden of poor mental health is high in young people and early intervention is key, so we must really start developing fun and engaging ways to get children to be more active. Of potential interest, we have shown a similar relationship in adults – if we replaced 30-60 minutes of sedentary time with activity we can reduce the new cases of depression.
4. The type of sedentary behaviour – “active” or “passive” makes a difference
We have undertaken a number of studies which have suggested that not all sedentary behaviour is equally bad for our mental health. In this research, we have categorised the context of sedentary behaviour and cognitive load/engagement. Passive sedentary behaviour is when our cognitive load is not high, for instance sitting and watching TV. Active sedentary behaviour includes activities where our minds are engaged, think working on a laptop or reading a stimulating article 😊.
In the first study, we investigated active and passive sedentary behaviours and future cases of depression in over 40,000 adults in Sweden over a 14 year period. We found that people who engaged in over 3 hours a day of mentally active sedentary behaviour were less likely to have depression in the future than those who engaged in under 3 hours of mentally active sedentary behaviour. We also showed a potential relationship with higher passive sedentary behaviour and an increased risk of depression.
In an associated study, we showed that if we replaced 30 minutes of passive sedentary behaviour with 30 minutes of mentally active behaviour we can potentially reduce 5% of cases of future depression.
As a person who sits a lot “thinking” or writing, I was particularly pleased about this emerging data.
To conclude, sedentary behaviour does appear to be associated with poor mental health. However, we can change this. Making small changes such as swapping activity for sitting time or reading a book instead of watching the TV could protect your mental health.
If you are keen to talk about harnessing the power of movement in practice, get in touch. For those interested I spend a lot of time talking about this topic and others in the courses I teach.
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