Chronic adversity dampens dopamine production

People exposed to a lifetime of psychosocial adversity may have an impaired ability to produce the dopamine levels needed for coping with acutely stressful situations according to a new study. The findings, published today in eLife, may help explain why long-term exposure to psychological trauma and abuse increases the risk of mental illness and addiction.

What the researchers say: "We already know that chronic psychosocial adversity can induce vulnerability to mental illnesses such as schizophrenia and depression," explains the lead author. "What we're missing is a precise mechanistic understanding of how this risk is increased."

To address this question, the researchers used an imaging technique called positron emission tomography (PET) to compare the production of dopamine in 34 volunteers exposed to an acute stress. Half of the participants had a high lifetime exposure to psychosocial stress, while the other half had low exposure. All of them undertook the Montréal Imaging Stress Task, which involved receiving criticism as they tried to complete mental arithmetic.

Two hours after this stress task, the participants were injected with small amounts of a radioactive tracer that allowed the scientists to view dopamine production in their brains using PET. The scans revealed that in those with low exposure to chronic adversity, dopamine production was proportional to the degree of threat that the person perceived.

In people with high exposure to chronic adversity, however, the perception of threat was exaggerated whilst their production of dopamine was impaired. The researchers found that other physiological responses to stress were also dampened in this group. For example, their blood pressure and cortisol levels did not increase as much as in the low-adversity group in response to stress.

"This study can't prove that chronic psychosocial stress causes mental illness or substance abuse later in life by lowering dopamine levels," the lead author cautions. "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."

So, what? From the results of past studies (reported in TR) this finding seems pretty obvious. What I would add is that the stress can well be from work experience not necessarily just childhood trauma. I would argue that the nature of modern-day work is so inherently stressful (the rate of workstress is increasing by 70% every 4 years according to recent studies) that the depletion of dopamine leading to addiction and anhedonia is a natural result. Indeed, in almost all studies—of which there have been many—have indicated that this is the case.