People who habitually use stimulants like cocaine and methamphetamine (also known as crystal meth) may find it trickier to make moral judgments as a result of changes to their brain connectivity. According to the authors of two new studies published in the journal Psychopharmacology, this may help to explain why such a high proportion of violent criminals in the US are also regular drug users.
Of course, the researchers do not rule out the possibility that they may have got things the wrong way round, and that faulty brain activity may actually be the reason for both the moral hesitancy and drug use of many criminals. However, the fact that they found a direct correlation between the duration of drug abuse and the degree of abnormal neural connectivity suggests that they may indeed be onto something.
To conduct their research, they recruited male inmates from prisons in New Mexico and Wisconsin, some of whom were substance users while others were not. Using MRI, they observed the brain activity of these prisoners as they took part in a “moral decision-making task”, during which they were presented with a range of hypothetical scenarios such as murder, slavery, charity and kindness, and asked to rate them as either morally positive or negative.
Compared to the non-drug users, those with a history of cocaine and methamphetamine use exhibit abnormal activity in several areas of the brain that are strongly associated with emotional regulation and decision making while making these distinctions.
For instance, the amygdala, which plays an important role in both fear and pleasure responses, normally works together with a brain region called the ventromedial prefrontal cortex (mvPFC) to reinforce learning experiences related to moral transgressions. However, cocaine and crystal meth users showed a reduction in activity in the amygdala and an increase in the mvPFC, creating a type of imbalance that has previously been associated with a heightened tendency to act immorally.
Activity in other brain regions involved in similar processes – such as the anterior (ACC) and posterior cingulate (PCC) – was also found to be reduced in long term drug users. As such, the researchers conclude that “poor decision-making, including antisocial behavior, in stimulant users may be related to abnormalities in the neural network responsible for evaluating and making decisions about moral situations.”
Exactly how drugs like cocaine and crystal meth generate these neurological imbalances in not yet known, however, so much more work is still needed before scientists can truly claim to have got to the bottom of this issue.
