A particular style of thinking that makes people vulnerable to depression can actually "rub off" on others, increasing their symptoms of depression six months later, a study has found.

Studies had shown that people, who respond negatively to stressful life events, interpreting the events as the result of factors they can`t change and as a reflection of their own deficiency, are more vulnerable to depression.
This "cognitive vulnerability" is such a potent risk factor for depression that it can be used to predict which individuals are likely to experience a depressive episode in the future, even if they`ve never had a depressive episode before.

Individual differences in this cognitive vulnerability seem to solidify in early adolescence and remain stable throughout adulthood, but psychological scientists Gerald Haeffel and Jennifer Hames of the University of Notre Dame predicted that it might still be malleable under certain circumstances.

The researchers hypothesized that cognitive vulnerability might be "contagious" during major life transitions, when our social environments are in flux. They tested their hypothesis using data from 103 randomly assigned roommate pairs, all of whom had just started college as freshmen.

Within one month of arriving on campus, the roommates completed an online questionnaire that included measures of cognitive vulnerability and depressive symptoms. They completed the same measures again 3 months and 6 months later; they also completed a measure of stressful life events at the two time points.

The results revealed that freshmen who were randomly assigned to a roommate with high levels of cognitive vulnerability were likely to "catch" their roommate`s cognitive style and develop higher levels of cognitive vulnerability; those assigned to roommates who had low initial levels of cognitive vulnerability experienced decreases in their own levels. The contagion effect was evident at both the 3-month and 6-month assessments.

Most importantly, changes in cognitive vulnerability affected risk for future depressive symptoms: Students who showed an increase in cognitive vulnerability in the first 3 months of college had nearly twice the level of depressive symptoms at 6 months than those who didn`t show such an increase.

The findings provide striking evidence for the contagion effect, confirming the researchers` initial hypothesis.

Based on these findings, Haeffel and Hames suggested that the contagion effect might be harnessed to help treat symptoms of depression.

According to the researchers, the results of this study indicate that it may be time to reconsider how we think about cognitive vulnerability.

The research has been published in Clinical Psychological Science, a journal of the Association for Psychological Science.