A healthy lifestyle that includes moderate alcohol consumption, a nutritious diet, regular physical activity, restful sleep and frequent socialising, while avoiding smoking and too much sedentary behaviour, reduces the risk of depression, new research suggests.
In research published today in Nature Mental Health, an international team of researchers, including from the University of Cambridge and Fudan University, looked at a combination of factors, including lifestyle, genetics, brain structure and our immune and metabolic systems, to identify the underlying mechanisms that might explain this link.
According to the World Health Organization, depression affects around one in 20 adults and is a significant public health burden worldwide. The factors that influence the onset of depression are complex and include a mixture of biological and lifestyle factors.
To better understand the relationship between these factors and depression, the researchers turned to the UK Biobank, a biomedical database and research resource containing anonymised genetic, lifestyle and health information about its participants.
Looking at data from almost 290,000 people – 13,000 of whom had depression – who were followed over a nine-year period, the team identified seven healthy lifestyle factors that were associated with a lower risk of depression. These were
- moderate alcohol consumption
- a healthy diet
- regular physical activity
- healthy sleep
- never smoking
- Low to moderate sedentary behaviour
- frequent social contact
Of all these factors, getting a good night’s sleep – between seven and nine hours a night – made the biggest difference, reducing the risk of depression, including single depressive episodes and treatment-resistant depression, by 22%.
Frequent social contact, which generally reduced the risk of depression by 18%, was the most protective against recurrent depression.
Moderate alcohol consumption reduced the risk of depression by 11%, a healthy diet by 6%, regular physical activity by 14%, never smoking by 20% and low-to-moderate physical activity by 13%.
Based on the number of healthy lifestyle factors an individual adhered to, they were assigned to one of three groups: unfavourable, intermediate and favourable lifestyle. People in the intermediate group were about 41% less likely to develop depression than those in the unfavourable lifestyle group, while those in the favourable lifestyle group were 57% less likely.
The team then examined the participants’ DNA and gave each a genetic risk score. This score was based on the number of genetic variants a person carried that are known to be associated with the risk of depression. Those with the lowest genetic risk score were 25% less likely to develop depression than those with the highest score – a much smaller effect than lifestyle.
The team also found that a healthy lifestyle can reduce the risk of depression in people at high, medium and low genetic risk for depression. This research highlights the importance of a healthy lifestyle in preventing depression, regardless of a person’s genetic risk.
Professor Barbara Sahakian, from the Department of Psychiatry at the University of Cambridge, said: “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.
“Some of these lifestyle factors are things we have some control over, so finding ways to improve them – for example, making sure we get a good night’s sleep and getting out to see friends – could make a real difference to people’s lives.”
To understand why a healthy lifestyle might reduce the risk of depression, the team looked at a number of other factors.
First, they looked at MRI brain scans of nearly 33,000 participants and found a number of regions of the brain where greater volume – more neurons and connections – was associated with a healthy lifestyle. These included the pallidum, thalamus, amygdala and hippocampus.
The team then looked for markers in the blood that indicated problems with the immune system or metabolism (how we process food and produce energy). Among the markers found to be related to lifestyle were C-reactive protein, a molecule produced in the body in response to stress, and triglycerides, one of the main forms of fat used by the body to store energy for later use.
A number of previous studies support these links. For example, exposure to stress in life can affect how well we are able to regulate blood sugar, which can lead to a deterioration in immune function and accelerate age-related damage to cells and molecules in the body. Physical inactivity and lack of sleep can damage the body’s ability to respond to stress. Loneliness and lack of social support have been shown to increase the risk of infection and increase markers of immune deficiency.
The team found that the pathway from lifestyle to immune and metabolic function was the most significant. In other words, a poorer lifestyle affects our immune system and metabolism, which in turn increases our risk of depression.
Dr Christelle Langley, also from the University of Cambridge’s Department of Psychiatry, said: “We’re used to thinking that a healthy lifestyle is important for 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”.
Professor Jianfeng Feng, from Fudan University and the University of Warwick, added: “We know that depression can start in adolescence or young adulthood, so educating young people about the importance of a healthy lifestyle and its impact on mental health should start in schools.
This study was supported by grants from organisations including the National Natural Science Foundation of China and the Ministry of Science, China.
