Drug Addiction: Is Brain Stimulation the Answer?

Transcranial magnetic brain stimulation has allowed researchers to reduce how "excited" the brains of chronic cocaine and alcohol users become in response to drug cues.

Drug addiction is a chronic disease affecting 5.4 percent of the population worldwide.

In 2016, more than 64,000 people in the United States are thought to have died from a drug overdose.

According to most recent estimates, about 21.5 million U.S. individuals aged 12 and above live with a substance abuse disorder.

While the exact causes of drug addiction are unknown and researchers do not yet fully understand what causes someone to become addicted to a drug, we do know that, over time, drug abuse triggers changes in the brain that perpetuate the addiction cycle.

For example, we now know that the brain's reward-processing circuits are thrown off balance in drug addiction, as the brain gets an excessive amount of the neurotransmitter dopamine.

Sometimes dubbed the "sex, drugs, and rock 'n' roll" neurotransmitter, dopamine plays a crucial role in reward-mediated motivation and learning, as well as in experiencing pleasure.

When the brain gets too much dopamine from drugs, it learns to continue to search for that "high" in favor of the "lesser" pleasure that it would normally get from other, daily rewards, such as consuming a chocolate bar or getting recognition at work.

These neurobiological underpinnings make addiction a so-called brain disease. Despite this, until now, researchers had not come up with treatments aimed at the neural circuits involved in the condition.

Now, however, researchers at the Medical University of South Carolina in Charleston may have found a treatment that successfully targets these brain circuits.

Supervised by Colleen Hanlon, Ph.D., researchers successfully used a noninvasive brain stimulation technique called transcranial magnetic stimulation (TMS) to blunt the brain's response to the appeal of alcohol and cocaine in chronic users.

Treating the brain's reward center

The researchers carried out two experiments at once, both of which were led by first study author Tonisha Kearney-Ramos, Ph.D. One study involved 24 participants with alcohol use disorder, and the second involved 25 participants with cocaine use disorder.

The study participants had one session of TMS and one control, or "sham," session that imitated a TMS session without delivering any stimulation to the brain.

TMS allows for specific targeting of brain areas. In these experiments, both groups of participants received stimulation that focused on a brain region key for addiction and reward-processing: the ventromedial prefrontal cortex.

After the sessions, Kearney-Ramos and colleagues took scans of the participants' brains using functional MRI in an effort to assess their response to drug cues such as seeing a liquor bottle.

TMS was found to have significantly reduced the brain's reactivity to drug cues.

Dr. Cameron Carter, the editor of the journal that published the findings, explains what the results mean for treating drug addiction.

"Since cue reactivity has previously been associated with abstinence," he says, "these [findings] suggest a common mechanism for treatment effects across disorders."

Kearney-Ramos and her colleagues conclude, "This is the first sham-controlled investigation to demonstrate, in two populations, that VMPFC [stimulation] can attenuate neural reactivity to drug and alcohol cues in frontostriatal circuits."

Hanlon also weighs in, saying, "Here, for the first time, we demonstrate that a new noninvasive brain stimulation technique may be the first tool available to fill [a] critical void in addiction treatment development."

"Therefore, these results have a tremendous potential to impact both basic discovery neuroscience as well as targeted clinical treatment development for substance dependence."

Colleen Hanlon, Ph.D.

"These results," the study authors conclude, "provide an empirical foundation for future clinical trials that may evaluate the efficacy, durability, and clinical implications of VMPFC [stimulation] to treat addictions."