People with high lifetime exposure to psychosocial stress had an impaired ability to produce the dopamine necessary for coping with a stressful situation, according to an imaging study published online in eLife.
The finding may shed light on why long-term psychological trauma and abuse increase a person’s risk of experiencing mental health and addiction disorders.
“We already know that chronic psychosocial adversity can induce vulnerability to mental illnesses such as schizophrenia and depression,” explained lead author Michael Bloomfield, PhD, of University College London in the United Kingdom. “What we’re missing is a precise mechanistic understanding of how this risk is increased.”
The study included 34 participants, half with high lifetime exposure to psychosocial stress and half with low exposure. The participants underwent a stress task that consisted of mentally solving math problems while receiving criticism. Two hours later, they were injected with a small amount of a radioactive tracer and underwent positron emission tomography (PET) brain scans so researchers could look at dopamine production.
Participants with high exposure to chronic adversity had an exaggerated perception of threat combined with impaired production of dopamine, while those with lower exposure to adversity had dopamine production proportionate to the degree of threat they perceived, according to the study.
Participants with chronic adversity also showed other dampened physiological responses to stress, including lower increases in blood pressure and cortisol levels compared with other participants.
“This study can’t prove that chronic psychosocial stress causes mental illness or substance abuse later in life by lowering dopamine levels,” said Dr. Bloomfield. “But we have provided a plausible mechanism for how chronic stress may increase the risk of mental illnesses by altering the brain’s dopamine system.”