Watching TV, Passive Sitting, Linked to a 43% Higher Risk of Depression

Not all sitting is created equal. Lounging mindlessly in front of a TV is more likely to lead to depression than engaging in desk-bound office tasks, according to new research in the Journal of Affective Disorders.

Led by Brazilian scientists, the study stands out for its nuanced approach to how sedentary activities may differ in how they affect mental health. It defined mentally-passive activities such as channel surfing as those requiring little cognitive engagement. Mentally-active behaviors were defined as those that involve more cognitive stimulation, like office work or reading.

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Exploring Inflammation’s Role

To explore sitting-related depression, the researchers analyzed data from the 1958 National Child Development Study, which records individuals born in a specific week of that year in the United Kingdom. From here, the researchers analyzed information from a total of 4607 participants, roughly divided between men and women. They then examined the subjects’ inflammatory markers, such as waist circumference, C-reactive protein, and glycated hemoglobin, to determine their role in linking sedentary behavior with depression.

The study revealed that participating in mentally-passive pastimes increased the likelihood of developing depression by 43 percent, compared to those who avoided such inactivities. On the other hand, the study found no significant association between mentally-active sedentary time and depression.

Waist circumference and levels of C-reactive protein, both markers of inflammation in the body, may partially explain how mentally-passivity is associated with depression. Each unit increase in waist circumference and C-reactive protein levels led to a 9.2 percent and 8.3 percent increase in the risk of depression, respectively. 

However, glycated hemoglobin, another inflammation marker, showed no statistical link between mentally-passive sedentary behavior and depression. The authors concluded that the absence of effect, evidenced by a less than 5 percent difference in depression risk regardless of glycated hemoglobin levels, underscored the intricacies of biological processes at play. Not all markers of inflammation seem to make the same contribution to depression risk, the researchers concluded. 

“Our findings also suggest that those at risk for depression and with high levels of mentally-passive sedentary behaviors could benefit from assistance to reduce waist circumference and C-reactive protein via increased levels of physical activity,” the authors wrote. 

Why It Matters

This study underscored the importance of distinguishing between different types of sedentary behavior in mental health research. The study challenges the common perception that all forms of sedentary behavior bestow the same level of harm. It suggests that the nature of the activity matters, and that the pathways affecting them, are complex and poorly understood. The distinction between cognitively-passive and cognitively-active behaviors is particularly crucial, as it implies that both physical and mental engagement while seated help shape mental health outcomes.

The implications of these findings are particularly relevant in the modern world where slothful lifestyles are the norm. According to a study published by the American Journal of Epidemiology, American adults, on average, spend about 6.4 hours a day parked in the seated position, though this varies based on factors like age, lifestyle and occupation. The typical office worker spends about 8.2 hours per day in a chair.

The researchers advocate for simple changes to make sitting time more engaging – and perhaps a more positive influence on mental health. For instance, they recommended replacing at least some TV time with more brain-stimulating endeavors like puzzle-solving or reading.

Furthermore, the study’s findings on the role of inflammation in linking sedentary behavior to depression could pave the way for novel preventative strategies. By focusing on reducing inflammation through lifestyle changes, such as diet and exercise, individuals could potentially mitigate the psychological risks associated with lack of movement. This “mind and body” approach may foster a more holistic view of health management, simultaneously addressing the mental and physical.

“While physical activity guidelines recommend reducing and breaking up sedentary time, our findings suggest that recommendations specific to mental health could emphasize reducing mentally-passive sedentary time,” the authors wrote.