A new study in the American Journal of Psychiatry has identified social connection as the strongest protective factor against depression, while also revealing that those who take fewer daytime naps and spend less time watching TV face a reduced risk of suffering from the condition. Significantly, results showed that even individuals with a genetic vulnerability to depression and those who have experienced early life trauma are less likely to develop depression if they have regular meaningful contact with other people.

Depression is the leading cause of disability worldwide and is treated with varying degrees of success using a range of different therapies and pharmaceuticals. Yet the authors of this latest study insist that the condition is still poorly understood, as a full investigation into the numerous risk factors for depression has never been conducted.

To remedy this, the researchers looked at data from a total of 123,794 adults who enrolled in the UK Biobank program, which aims to investigate how genetics and environmental factors combine to generate various illnesses. Specifically, the study authors examined information relating to individuals who displayed no depressive symptoms upon enrollment, but who went on to develop clinical depression six to eight years later.

This enabled the researchers to identify 106 lifestyle factors that appear to influence a person’s risk of developing depression. These include sleep patterns, exercise habits, social interactions, media use, diet, and environmental conditions.

Next, the team used a statistical analysis method known as Mendelian randomization (MR) in order to determine which of these risk factors had a causal relationship to depression and which were simply correlated with depression. Only a few of the original 106 lifestyle elements were found to be genuine risk factors, with social interaction being the most significant.

“Far and away the most prominent of these factors was frequency of confiding in others, but also visits with family and friends, all of which highlighted the important protective effect of social connection and social cohesion,” explained study author Jordan Smoller, associate chief for research at the Massachusetts General Hospital's Department of Psychiatry, in a statement.

Meanwhile, a tendency to take daytime naps was also found to increase the risk of depression, although the study authors say that more research is needed to verify this, as it could be that depression actually causes increased napping.

Similarly, the amount of time spent watching television appears to partially determine a person’s odds of suffering from depression, yet the researchers say this may not necessarily have anything to do with screen time per se as watching TV could in fact just be a proxy for being sedentary. The effects of sedentary behavior were not examined in their own right in this study, although the authors concede that this has previously been identified as a risk factor for depression.

Summing up their findings, the researchers insist that “efforts to counteract disconnection at the societal and individual levels – whether by social activity prescriptions or reducing the stigma of seeking emotional support – should be central to an effective depression prevention agenda.”