Depression and the emotions associated with it can be contagious, according to a new study.
Researchers have found that the gloomy mindset of students vulnerable to depression can be catching, making their friends more likely to suffer the condition six months later.
The research follows studies showing that people who respond negatively to stressful life events - interpreting them as the result of factors they can't change and as a reflection of their own shortcomings - are more vulnerable to depression.
This "cognitive vulnerability" is such a strong risk factor for depression that it can be used to predict who is likely to experience depression in the future.
Doctors Gerald Haeffel and Jennifer Hames, of Indiana's University of Notre Dame, said that this vulnerability seemed to establish itself in early adolescence but remain stable throughout adulthood.
They decided to investigate whether it might be "contagious" during major life transitions such as starting at university.
They followed 206 room mates who had been paired up randomly, all of whom had just started their first year of university.
The results revealed that students who were assigned to a room mate with high levels of cognitive vulnerability were likely to "catch" their room mate's style of thinking and develop a vulnerability to depression themselves.
The reverse was also true. Those assigned to room mates who were not prone to depression experienced decreases in their own levels negative thinking.
The result showed that students who developed an increase in depressive thinking in the first three months of college, had nearly twice the level of depressive symptoms at six months than those who didn't show such an increase.
Dr Haeffel said it provided "striking evidence" for the contagion theory.
He added that the findings suggest that altering a person's environment could be used a part of a treatment for depression because a person's vulnerability fluctuates over time.
"Our study demonstrates that cognitive vulnerability has the potential to wax and wane over time depending on the social context," he said.
"This means that cognitive vulnerability should be thought of as plastic rather than immutable."
The research is published in the journal Clinical Psychological Science.
- DAILY MAIL