Among the many promising treatments for addiction that researchers are actively pursuing, transcranial magnetic stimulation (TMS) may be the most intriguing. TMS may not only potentially suppress cravings for smoking or drinking, but also may reveal brain locations and activities related to addiction.
“TMS is a noninvasive tool for modulating brain activity in a living person,” David Gorelick, M.D., Ph.D., a staff clinician at the Intramural Research Program at the National Institute on Drug Abuse (NIDA) told Psychiatric News. Gorelick is leading a clinical trial to assess whether TMS can suppress cravings in people who are addicted to nicotine. If the answer is yes, TMS might help smokers quit and prevent relapses.
Unlike psychoactive drugs, which alter brain activities chemically, TMS does so with electricity. A magnetic field, generated by an electrical current running through a coil inside the device, is applied to the scalp and induces a weak electrical current in the corresponding brain region.
TMS has been used primarily to treat major depressive disorder since it was approved by the Food and Drug Administration in 2008. However, researchers hope it can also work for other neurological and psychiatric disorders.
“[TMS] can have some practical and safety advantages over ECT [electroconvulsive therapy] and medications,” Gorelick explained. Unlike ECT, TMS does not require general anesthesia or cause seizures. And it is safer than some psychoactive medications during pregnancy.
The possible effect of TMS on addictions has been tested in several small studies. For example, Jed Rose and colleagues reported in the October 15, 2011, Biological Psychiatry that repetitive TMS (rTMS) significantly suppressed cravings in 15 smokers given visual cues, in this case, pictures of smoking.
Revital Amiaz and others gave 48 chronic smokers either high-frequency rTMS or sham stimulation for 10 days. The rTMS treatment was shown to significantly reduce both cue-induced craving and the number of cigarettes smoked. The study appeared in the April 2009 Addiction.
In a study published in the January 2010 Addiction, Biswa Mishra and colleagues gave rTMS to 30 patients with alcohol dependence. After 10 sessions, these patients reported statistically significant decreases in cravings for alcohol compared with 15 patients who received sham stimulation.
Currently, TMS research on addiction tends to aim the magnetic field at the dorsolateral prefrontal cortex (DLPFC), the same region targeted in depression. In the ongoing NIDA-funded study, Gorelick adds an extra step of neuronavigation before TMS to find and target the exact brain region associated with nicotine cravings.
Gorelick credits Paul Fitzgerald, M.B.B.S., Ph.D., and collaborators at the Alfred and Monash University in Melbourne, Australia, for laying the groundwork of functional magnetic resonance (fMRI)-guided TMS treatment. They demonstrated that the commonly used method of finding the scalp location directly above DLPFC, known as the “5 cm method,” is crude and inaccurate. “In up to half of the treated patients, you miss the target region,” said Gorelick. Fitzgerald’s study was published in Neuropsychopharmacology in April 2009.
To find the right location to stimulate, Gorelick and colleagues first give their study participants an MRI scan while they look at smoking-related photos (cues). The brain scans are compared with scans taken with neutral cues to identify the brain regions activated by smoking cues. Only the cortical regions can be affected by TMS treatment, because the magnetic pulses can reach only 2 cm deep into the brain.
“We have seen great variations in the target region,” said Gorelick. “Some people have their greatest activities on the right side, and some on the left side.” Once the target location in each person is mapped, he or she receives daily TMS sessions for five days. High-frequency magnetic pulses are applied to an individual target region while the participant is looking at visual cues. The hypothesis is that cue-induced cravings are tempered by the stimulation.
Upon study conclusion, the study participants undergo the fMRI again to compare their brain activity in response to smoking cues with baseline data. Actual reduction in nicotine use, measured by urine and breath tests, is also analyzed.
Because the study is double blind, Gorelick does not yet know whether TMS is more effective than sham stimulation. However, in participants who have completed the study, “we are seeing brain changes…. We just don’t know whether these came from the active treatment group or the sham group,” he said.
Even if the study is successful, other questions remain before TMS can be used for smoking cessation in clinics, Gorelick cautioned. It is unknown how long the effectiveness lasts or whether suppressing cue-induced craving is sufficient to significantly reduce or stop smoking. The fMRI scan can add cost to personalized TMS treatment, but it may also illuminate individual variations in the addicted brain.
On the horizon is a “deep TMS” device that can penetrate the brain deeper than conventional TMS, purportedly below the cortex. The unique shape and organization of current flow within the coils induce a summation of electromagnetic fields that are larger than those from standard TMS coils, according to Prof. Abraham Zangen, one of the inventors of the device and chair of the Biology-Psychology Program at Ben Gurion University in Israel. “In addition, these coils are more flexible to allow tight attachment to the scalp and avoid non-tangential coil elements in the parts that are closer to the brain target,” Zangen explained.
Brainsway, an Israeli company, is testing this deep TMS device in clinical trials to treat several neuropsychiatric disorders, including addiction and eating disorders.
In 2011, Brainsway announced favorable interim results from a study in which deep TMS therapy significantly reduced alcohol consumption compared with sham stimulation in 13 patients with alcohol dependence. In another study, high-frequency stimulation from the deep TMS therapy was more effective than sham stimulation in reducing cigarette smoking in 46 smokers with chronic obstructive pulmonary disease.
“These were heavy smokers who did not respond to previous treatments,” Zangen noted. “The group treated at high frequency [TMS] had a very significant reduction in smoking, and 40 percent stopped smoking already in the interim analysis.”