Children whose grandmothers were stressed during pregnancy have an increased chance of mental health problems, a study suggests.
The effects of maternal stress during pregnancy can be transmitted to both the first and second generation of offspring, research carried out in rats has shown.
The study found that increased anxiety is linked to changes in genes expressed in the part of the brain that regulates emotions such as fear and anxiety.
Previous research suggests that stress during pregnancy is harmful to developing babies' brains and is linked to a greater risk of mental health disorders.
However, until now it was not known that the harmful effects of prenatal stress could present themselves in future generations, the team says.
Researchers found that the second generation of offspring from rats who had experienced social stress during pregnancy - caused by short periods of exposure to unfamiliar female rats - were more anxious than those whose grandmothers had not experienced stress.
These offspring showed a pattern of gene expression in a region of the brain - known as the amygdala - that is linked with an increased risk of anxiety disorders.
The findings provide researchers with greater insight into the origins of mood disorders. Understanding the mechanisms that allow the effects of stress to be transmitted to future generations could help researchers find new ways of treating some mental health conditions, the team says.
The research, published in the journal Psychoneuroendocrinology, was supported by the Biotechnology and Biological Sciences Research Council.
Dr. Paula Brunton, of The Roslin Institute at the University of Edinburgh, who led the study, said: "It appears from this work that stress during pregnancy has long term health implications not only for the unborn child but also for future generations."