In their recent editorial, Carter & Hall  propose that the trial of deep brain stimulation (DBS) for addiction is premature due to expenses, possible risks and the assumed poor scientific rationale of the method in this field. Because our groups have published the first reports on the benefit of DBS of the nucleus accumbens (NAcc) for the treatment of otherwise treatment-resistant addiction [2–5], we would like to take this opportunity to clarify our view on the scientific base for the use of DBS in addiction. Undoubtedly, the invasiveness of the method and the accompanying risks should be kept in mind and always require extensive evaluation (Primum non nocere!). A recent comprehensive review of DBS for Parkinson disease  estimated the risk of an intracerebral haemorrhage as less than 2%, whereas the Cologne centre reported this rate to be as low as 0.2% , with perioperative intricacies cumulating to 4.2%. Adverse effects not related directly to the surgical procedure (assumed cognitive, behavioural or emotional changes) are not generalizable, but are specific to the stimulated target region. Reports on larger (>10 patients) series with NAcc stimulation for obsessive–compulsive disorder and depression are sparse, but none reports adverse permanent changes or impairment [8–11]. Only one study reported mild permanent side effects of the stimulation, such as forgetfulness or difficulties finding words in some patients .
The high effect size of improvement in mobility through DBS of the nucleus subthalamicus in Parkinson disease , the associated improvement in quality of life led, besides other aspects, to the study of DBS in mental disorders that proved to be refractory to any other treatment options. In the past, specific targets for new indications were chosen based on experiences with lesional procedures. Nowadays, profound hypotheses and translational support, for example by valid animal models, are needed and stipulated before choosing a new target for DBS. In addiction, the use of the NAcc as a novel target for DBS fulfils these criteria: the role of the NAcc in addiction seems to be established (e.g. ) and recent valid animal studies show significant induced improvement in cocaine, morphine and alcohol addition behaviour following DBS of the NAcc [14–17]. Coincidental single-case findings  and retrospective inquiries  may support the translational generalization to humans. Fewer than 50% of all patients with alcohol addiction achieve long-term abstinence by currently available therapies, and direct as well as indirect costs associated with addiction are very high . By contrast, the few patients who underwent DBS surgery for addiction remained abstinent or had a major reduction of relapses [3–5].
Concluding, the trial of DBS as potential treatment option for alcohol dependence (and potentially other addictions) through large multi-centred studies is reasonable and necessary. With the low risk of harm as described above it is a scientific and ethical imperative (e.g. ) to strive for a potentially promising new treatment in a disorder with a high number of patients who cannot be helped otherwise and of whom much too large a number end their lives by committing suicide.