W.H.O. reports that 1 in 20 adults will experience a form of depression at some point in their life, and major depressive disorder poses a significant burden on global public health. Factors that influence the onset of depression can vary from person to person and they can be complicated as well as include a mixture of biological and lifestyle factors.
To gain a better understanding between these factors and depression the researchers leveraged data from the UK Biobank. The team of international researchers looked at a combination of factors which included brain structure, genetics, lifestyle factors, and the immune and metabolic systems to identify the underlying mechanisms that might explain the link between depression and a healthy lifestyle.
The team analyzed data from almost 290,000 individuals, of whom 13,000 had depression, and they were followed for a 9-year study period, during which time 7 healthy lifestyle factors were identified that were linked to a lower risk of depression: never smoking, frequent social connection, regular physical activity, a healthful diet, low alcohol consumption in moderation, good sleep hygiene, and limited sedentary behavior.
However, out of the seven health factors, getting good sleep, between 7-9 hours a night, was observed to make the biggest difference in helping to reduce the risk of depression, including single-depressive episodes and treatment-resistant depression by 22%. Additionally, frequent social interactions in general were found to decrease the risk of depression by 18% and it was the most protective against recurrent depressive disorder.
Never smoking was found to have decreased the risk by 20%, regular physical activity reduced the risk by 14%, limiting sedentary behaviors decreased the risk by 13%, low consumption of alcohol in moderation reduced the risk of depression by 11%, and maintaining a healthful diet decreased the risk of depression by 6%.
According to the researchers, the participants were assigned to one of three groups according to the number of healthy lifestyle factors they adhered to: Favorable, intermediate, and unfavorable. Those in the intermediate groups were found to be 41% less likely to develop depression compared to those in the unfavorable lifestyle groups, and those in the favorable lifestyle group were found to be 57% less likely.
Participants were also assigned a genetic risk score after the researchers examined the DNA of each person. Scores were based on the number of genetic variants carried by the person that have known links to depression. The researchers report that those with the lowest risk scores were 25% less likely to develop depression compared to those with the highest scores. Additionally, in those at low, medium, and high genetic risk for depression further investigation revealed that a healthy lifestyle can help to lower the risk of depression, underlying the importance of maintaining a healthy lifestyle to prevention against depression, regardless of genetic risk.
“Although our DNA – the genetic hand we’ve been dealt – can increase our risk of depression, we’ve shown that a healthy lifestyle is potentially more important,” said Professor Barbara Sahakian, from the Department of Psychiatry at the University of Cambridge. “Some of these lifestyle factors are things we have a degree control over, so trying to find ways to improve them – making sure we have a good night’s sleep and getting out to see friends, for example – could make a real difference to people’s lives.”
To investigate why a healthy lifestyle may help to reduce the risk of depression a number of factors were examined, including analyzing close to 33,000 MRIs which revealed a number of regions in the brain where a larger volume of neurons of connections was linked to maintaining a healthy lifestyle. These regions included the hippocampus, amygdala, pallidum, and the thalamus.
When examining markers in the blood for markers indicating problems with the immune system or metabolism, among those found to be linked to lifestyle were C-reactive protein and triglycerides, and previous studies are supportive of these links.
Overall, numerous previous studies support all of the researchers’ links found in this study. For example, exposure to stress can affect how well blood sugar is regulated, which can lead to the deterioration of immune functions and accelerated age-related damage to cells and molecules within the body. Maintaining a sedentary lifestyle and insufficient sleep can restrict the body’s ability to respond to stress, and loneliness/lack of social support have been found to increase the risk of infections as well as increase markers of immune deficiency.
The researchers suggest that the pathway from lifestyle to immune and metabolic functions was found to be the most significant, meaning that a poorer lifestyle impacts our immune system as well as our metabolism which in turn increases the risk of depression.
“We’re used to thinking of a healthy lifestyle as being important to our physical health, but it’s just as important for our mental health. It’s good for our brain health and cognition, but also indirectly by promoting a healthier immune system and better metabolism,” said Dr Christelle Langley, who is also from the Department of Psychiatry at the University of Cambridge.
Professor Jianfeng Feng, from Fudan University and Warwick University, added: “We know that depression can start as early as in adolescence or young adulthood, so educating young people on the importance of a healthy lifestyle and its impact on mental health should begin in schools.”
