A group of smokers were suddenly relieved of their nicotine addiction following brain damage, suggesting a network of interconnected brain regions may be the underlying basis of many addictions, according to a new study published in Nature Medicine.
Study details and key findings
For the study, researchers analyzed two cohorts of patients from the University of Iowa and the University of Rochester who were addicted to nicotine cigarettes at the time of focal brain damage. In total, 129 patients were included in the analysis, and 53% had continued smoking while 26% met the criteria for addiction remission. On average, patients had smoked 23.1 cigarettes per day at the time of their brain injury.
Initially, the researchers found that the location of lesions were quite variable among patients who had experienced smoking remission. However, after using a technique called lesion network mapping, they were able to determine the lesions found in patients who quit smoking were mapped to a connected brain circuit, which the researchers called the "addiction remission network."
In particular, lesions positively connected to the cingulate and insula and negatively connected to the medial prefrontal cortex were more likely to be associated with smoking remission in patients. Conversely, legions with opposite connectivity profiles were the least likely to lead to remission.
To determine the generalizability of their findings, the researchers also examined 186 patients with brain lesions who had completed an alcoholism risk assessment. They found that lesions associated with lower alcoholism risk had similar connectivity to lesions that disrupted nicotine addiction in the first group of patients, even after controlling for smoking status—suggesting that this particular brain circuit may be the underlying basis of many addictive behaviors.
According to the New York Times, some independent experts said the study's findings were "an unusually powerful demonstration of the brain's role in substance use disorders."
"I think this could be one of the most influential publications not only of the year, but of the decade," said A. Thomas McLellan, professor emeritus of psychiatry at the University of Pennsylvania and a former deputy director of the Office of National Drug Control Policy. "It puts to rest so many of the stereotypes that still pervade the field of addiction: that addiction is bad parenting, addiction is weak personality, addiction is a lack of morality."
In addition, Juho Joutsa, one of the study's lead authors and a neurologist at the University of Turku in Finland, said the study's findings may help researchers develop more targeted treatments for people with smoking or other addictions.
"One of the biggest problems in addiction is that we don't really know where in the brain the main problem lies that we should target with treatment," Joutsa said. "We are hoping that after this, we have a very good idea of those regions and networks."
So far, electrical stimulation of the brain, which can mimic the effect of an injury or excite activity in different regions, has been used to treat depression and obsessive-compulsive disorder, but similar therapies for addictions remain sparse.
According to Judy Luigjes, an assistant professor of psychiatry at Amsterdam University Medical Centers, some patients with substance use disorders may be reluctant to participate in trials of brain stimulation treatments because their motivation to treat the disease can fluctuate and make it more difficult to take part in time-intensive treatments.
Structural challenges may also limit patients' access to these treatments, although some researchers are working to address these concerns. For example, an addiction team at Mount Sinai Health System have begun administering less invasive brain stimulation treatments to patients in their homes or at community centers rather than in hospitals.
However, Luigjes noted that while the brain is an important entry point for addiction treatment, addressing social and environmental factors that contribute to addiction may ultimately be more beneficial and impactful for patients.
"We've put too much of our hopes and money and energy into one side [brain stimulation]," she said. "I don't know if it will pay out in the way we thought it would." (Mueller, New York Times, 6/13; Fauzia, Daily Beast, 6/13; Joutsa et al., Nature Medicine, 6/13)