You can 'pick up' a good or bad mood from your friends.

 Fortunately, depression doesn't have the same effect.

The new research suggests that both good and bad moods can be 'picked up' from friends, but depression can't.

What the researchers say: The team analyzed data from the National Longitudinal Study of Adolescent to Adult Health which incorporates the moods and friendship networks in the US. Their paper has been published in the journal Royal Society Open Science. The team's findings imply that mood does spread over friendship networks, as do various different symptoms of depression such as helplessness and loss of interest. However, they also found that the effect from lower or worse mood friends was not strong enough to push the other friends into depression. This is interesting because it contradicts earlier (from the 1990s) research that tended to show that depression could be spread rather like an epidemic among friendship or work groups.

Using mathematical modeling they found that having more friends who suffer worse moods is associated with a higher probability of an individual experiencing low moods and a decreased probability of improving. They found the opposite applied to those who had a more positive social circle.

“We investigated whether there is evidence for the individual components of mood (such as appetite, tiredness, and sleep) spreading through US adolescent friendship networks while adjusting for confounding by modeling the transition probabilities of changing mood state over time,” said the research leader. “Evidence suggests mood may spread from person to person via a process known as social contagion. Previous studies have found social support and befriending to be beneficial to mood disorders while recent experiments suggest that an individual's emotional state can be affected by exposure to the emotional expressions of social contacts.

“Clearly, a greater understanding of how changes in the mood of adolescents are affected by the mood of their friends would be beneficial in informing interventions tackling adolescent depression.”

The World Health Organization has estimated that depression affects 350 million people across the world, impacting on individual's abilities to work and socialize. This study's findings emphasize the need to also consider those who exhibit levels of depressive symptoms just below those needed for a diagnosis of actual depression when designing public health interventions.

The study also helps confirm that there is more to depression than simply low mood. At the individual level, these findings imply that following the evidence-based advice for improving mood, e.g. exercise, sleeping well, and managing stress, can help a person’s friends as well as themselves. Whilst for depression, depressed friends do not put an individual at risk of depressive illness so a recommended course of action would be to show them support.

Although the research was done primarily with adolescent friendship circles, the researchers claim that their findings would apply to all friendship or work colleague groups.

“The results found here can inform public health policy and the design of interventions for depression in adolescents. Sub-threshold levels of depressive symptoms in adolescents is an issue of great current concern as they have been found to be very common, to cause a reduced quality of life and to lead to greater risk of depression later on in life than having no symptoms at all,” noted the researchers.

“Understanding that these components of mood can spread socially suggests that while the primary target of social interventions should be to increase friendships because of their benefits in reducing the risk of depression, a secondary aim could be to reduce spreading of negative mood,” they concluded.

So what? It has been known for some time that moods were contagious—indeed it was something that Alicia and I wrote about in our book “Creating Optimism” (McGraw-Hill) a few years ago. Other research has indicated that moods can spread through workplaces and even societies. A number of corporations have been described as “depressed,” and this pervading negative mood has certainly affected their productivity, profitability and share price.

It has also been shown by prior recent research that other mental states—especially optimism, pessimism, defeatism, and resilience can be contagious. It all points to the fact that humans are social animals and as such we are profoundly affected by the mood as well as the attitudes of the people we are surrounded by.

Research has also shown that we physically as well as mentally synchronize with those that we work closely with or live with. We fall into step when walking with people we’re close to. Further, a woman’s menstrual cycle will tend to fall into line with those of her fellow workers. It might be said that the timing of that, too, was contagious.

Other research—detailed in previous TRs—has shown that the mood of a leader can have a profound effect on his or her followers. A pessimistic CEO can create an underperforming company or firm.

What now? Far too little research has been done in this area. However what we do know is that if you take a depressed, pessimistic employee and move them into a group of colleagues who are upbeat and optimistic their mood will most likely improve over time. It’s important also to be aware of the mood of leaders at all levels because of the knock-on effect mood and mental outlook—however, I am not suggesting manic supervisors!