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Nicotine is a highly addictive drug, and it is extremely difficult to quit smoking. Underscoring the addictive properties of nicotine, current estimates indicate that smoking just 100 cigarettes puts an individual at high risk of becoming a nicotine-dependent smoker. The good news is that the percent of the U.S. population who are active smokers has decreased substantially since the early 1960s. The bad news is that 20 to 25% of adults still smoke.
Survey studies suggest that a large majority of persons who smoke would like to quit. However, fewer than 10% of those attempting to quit are successful. Current treatment approaches can perhaps double this quit rate; nevertheless, overall success remains low and relapse is high.
A person becomes addicted to cigarettes because brain pathways are rewired as a result of repeated nicotine exposure. The nicotine-induced rewiring of emotional, motivational, and cognitive brain circuits leads to the need for continued, repeated, nicotine exposure in order for the addicted person to avoid very uncomfortable emotional and physical withdrawal symptoms.
In recent years, transcranial magnetic stimulation (TMS) has been explored as a treatment for a variety of psychiatric disorders, including major depression. This procedure utilizes electromagnets to stimulate specific brain regions, typically in the superficial layers of the neocortex (the outermost regions of the brain). Recently, TMS devices have been developed that are capable of influencing deeper regions of the cerebral cortex than had been accessible previously. Certain brain regions involved in addictive behaviors, including part of the cortex called the insula, can now be modulated with TMS.
Researchers from Israel recently published a potentially important study exploring the effect of TMS on smoking cessation. These investigators directed TMS to deep brain regions, including the insula, and compared the effects of high frequency magnetic pulses, low frequency magnetic pulses, and no (sham) magnetic pulses.
Initial results are promising. Administration of 13 TMS sessions over a 3-week period utilizing high frequency stimulation led to substantially higher rates of abstinence. Low frequency stimulation and sham stimulation had no influence. Following the 13 sessions, 35% of those in the high frequency stimulation group were abstinent compared to 7% in the low frequency and sham groups. Six months later, 28% of those who had received high frequency treatments remained abstinent, compared to 7% in the low frequency group and 5% in the sham group.
How does high frequency TMS work? It is thought that electrical currents induced in deep brain regions by magnetic stimulation alter the function of pathways that were rewired by nicotine. Better definition of these pathways is a goal of future research.
Naturally, the results of this pilot study must be replicated by other investigators in larger groups of subjects, but the present results indicate that TMS might help a significant percentage of people quit smoking. Many questions remain unanswered. Would individual or group psychotherapy and pharmacotherapy together with TMS lead to even better outcomes? Will further work varying the number of treatments, frequency of pulses, and location of magnets lead to treatment modifications that improve outcomes?
Despite limitations in the present study, it is clear that more effective and longer-lasting treatments for nicotine dependence are needed to reduce the individual and public health costs of cigarette smoking.
This column was co-written by Eugene Rubin MD, PhD and Charles Zorumski MD.
