A genetic link between stress and depression has been discovered by researchers.
The study, led by scientists at the University of Michigan, found that individuals who produce lower amounts of brain chemical neuropeptide Y (NPY) may have an increased chance of developing a major depressive disorder.
It was found that those with lower levels of NPY, which helps to restore calm following stressful events, experience significantly stronger brain responses to negative stimuli.
In addition, they also exhibited more powerful psychological responses to physical pain.
Lead author Dr Brian Mickey said: "These are genetic features that can be measured in any person. We hope they can guide us toward assessing an individual's risk for developing depression and anxiety."
Meanwhile, the government's mental health strategy has failed to take into account the impact of dysfunctional families, critics have said.
According to think tank The Centre for Social Justice, ministers should have assessed the effects of family breakdown as it is considered to be a major factor in mental health.