Depression sucks. No one likes to be around someone who is moping and despondent, but can some of that bleak thinking rub off on others? Is it possible to ‘catch’ symptoms of depression just from living with someone?

According to an article in Science Daily, the answer is affirmative. A study from the University of Notre Dame, published in Clinical Psychological Science, found that people who are “cognitively vulnerable”—i.e. respond negatively to stressful happenings in their lives—are more susceptible to depression, even if they’ve never experienced depressive episodes in the past. 

Researchers claim that levels of this so-called cognitive vulnerability (CV) are set in early adolescence and remain thus throughout adulthood. However, certain trigger life events, such as major transitions, can make us more vulnerable to depression. In such circumstances, depression may actually be contagious.

Data from 103 randomly thrown together roommates in college were measured at various stages for cognitive vulnerability and depressive symptoms. You guessed it: those with roommates with higher levels of CV reported more depressive symptoms in the future. And conversely, those rooming with someone having lower levels of CV found a decrease in their own levels over time.

So the contagion theory holds up for the most part, meaning that science may be able to change depressive outcomes simply by manipulating environmental conditions.

"Our findings suggest that it may be possible to use an individual's social environment as part of the intervention process, either as a supplement to existing cognitive interventions or possibly as a stand-alone intervention," wrote the researchers. "Surrounding a person with others who exhibit an adaptive cognitive style should help to facilitate cognitive change in therapy."

So there you have it, surrounding yourself with sunny people may actually serve as a crucial defense mechanism.