Researchers noted that a low-cost one-time intervention that educates teens about the changeable nature of personality traits helps  lower depression symptoms among them.

The study was conducted by researchers from The University of Texas at Austin. The researchers said their findings were important because till date few interventions have successfully prevented the onset of depressive symptoms among high schoolers.

"We were amazed that a brief exposure to the message that people can change, during a key transition - the first few weeks of high school - could prevent increases in symptoms of depression," said lead author David Scott Yeager in apress statement. "It doesn't come close to solving the whole problem. Yet finding anything promising has the potential to be important because prevention is far better than treatment - not only for financial reasons but also because it avoids human suffering."

The study was conducted in  about 600 ninth graders across three different high schools. The study started at the beginning of a school year, which is usually in September. The students were randomly assigned to participate in the treatment intervention or a similar control activity, though they were not aware of the group assignment. Both activities took place during a normal class period and required only paper or a computer. No one at the school knew the messages or reinforced them.

A follow-up study was conducted 9 months later. Researchers found that rates of clinically significant depressive symptoms rose by roughly 39 percent among students in the control group. On the other hand, students who learnt about the malleability of personality showed no such increase in depressive symptoms, even if they were bullied.

"The findings replicate in three independent samples, but we know almost nothing about the boundary conditions of these effects or whether they will continue to show up in future studies," said Yeager. "For example, will this intervention work equally well for all students? What symptoms are most affected or least affected? Are there any negative side-effects? We think timing really matters - will the intervention work even just a few months later in freshman year? Could you do it one-on-one in clinical practice? We don't have good answers to these questions yet."

The study was published online in journal Clinical Psychological Science, a journal of the Association for Psychological Science.  The project received funding from the Thrive Foundation for Youth, the Spencer Foundation, and the Raikes Foundation.