It’s estimated that one in fifteen Americans, about 21 million adults, is living with major . Yes, most of us feel down in the dumps from time to time, but depression is different. Depression is a never ending feeling of sadness that affects how you think, how you feel, and how you behave. For people living with a major depressive disorder, life seems bleak, not worth living. Everything is grey.

A variety of factors, ranging from to , are known to contribute to the likelihood you will develop depression. New research published last month in the journal Clinical Psychological Science adds to this list of factors by showing that the company you keep can affect how likely you are to develop depressive symptoms. That’s right, just being around someone with a cognitive vulnerability to depression—a tendency to focus on one's negative mood and to ruminate about it—seems to have a contagion effect, whereby this vulnerability to depression can rub off and make you more likely to develop depressive symptoms yourself.

What’s the evidence to support the idea that a cognitive vulnerability to depression can be contagious? Researchers at Notre Dame University recruited over 100 pairs of roommates just starting off their freshman year. Roommates at the large Midwestern university the researchers studied, by the way, are randomly assigned to live together via a computer selection system. People don’t pick who they are going to live with and all freshman are required to live on campus.

The researchers asked both roommates to complete measures of cognitive vulnerability (basically their tendency to focus on their negative mood and to ruminate about it), measures of the occurrence of events in their lives, and questionnaires intended to capture their depressive symptoms 3 times over a six month period. The first time the roommates filled out the measures was within one month of arriving on campus.

So, what did they find? In short, a student’s level of cognitive vulnerability three and six months out was significantly affected by his/her roommate’s cognitive vulnerability at initial testing (and vice versa). And, the more someone increased in cognitive variability across the school year, the more likely they were to develop symptoms of depression in response to stressful life events.

The take home: cognitive vulnerability to depression seems to be contagious. College students’ level of cognitive vulnerability, which has implications for developing depressive symptoms, is influenced by their roommates. And, although more work is needed to determine whether these findings hold for people outside their college years and who are not experiencing dramatic changes in their social environments (that is, moving away to college), the work is intriguing in that it suggests that we might “catch” ways of interpreting stressful life events and our resulting moods from those around us.

For more on how our feelings and emotions impact performance, check out my book “Choke”

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Haeffel, . J. et al. (2014). Cognitive vulnerability to depression can be contagious. Clinical Psychological Science.