Previous studies have suggested that glutamatergic dysfunction may play a role in the pathophysiology of compulsive and related disorders, and N-acetylcysteine—an amino acid known to increase extracellular levels of glutamate in the nucleus accumbens—may help to reduce these behaviors.
To test whether N-acetylcysteine was more effective than placebo in decreasing compulsive skin-picking behaviors, Jon Grant, J.D., M.D., M.P.H., a professor of psychiatry and behavioral neuroscience at the University of Chicago, and colleagues randomly assigned 66 adults aged 18 to 65 with a current DSM-5 diagnosis of excoriation disorder to 12 weeks of daily N-acetylcysteine (1,200 mg/day to 3,000 mg/day) or placebo treatment. Every three weeks, researchers evaluated the participants, using measures of skin-picking severity, including the modified Yale-Brown Obsessive Compulsive Scale (NE-YBOCS) and the Clinical Global Impression-Severity Scale.
Of the 66 participants in the trial, 59 were women, with a mean age of 34.8 years. At the end of 12 weeks, the NE-YBOCS total score demonstrated a 38.3% reduction in skin-picking symptoms for the N-acetylcysteine group (from 18.9 at baseline to 11.5 at 12 weeks) compared with 19.3% for placebo (from 17.9 at baseline to 14.1 at 12 weeks). The CGI-Improvement Scale score also demonstrated significant improvement by study end point: of the 32 participants who completed the study, 15 (47%) participants assigned to treatment with N-acetylcysteine were much or very much improved compared with 4 (19%) of the 21 in the placebo group who completed the study. However, treatment with N-acetylcysteine failed to produce statistically significant improvement in measures of psychosocial functioning or quality of life.
The authors offered several explanations as to why significant improvements in psychosocial or quality of life were not seen in the small trial, including the limitations of not assessing functional and quality-of-life improvements over a longer period of time. Another limitation was that the study did not include psychotherapy, which has been found to benefit patients with skin-picking disorder, they noted.
Nonetheless, the authors concluded, “This investigation suggests that N-acetylcysteine appears to be effective and well tolerated in the acute treatment of SPD [skin-picking disorder]. As effective treatments for skin picking emerge, it becomes increasingly important that physicians and other mental health care professionals screen for the disorder to provide timely treatment.”
For related information, see the Psychiatric News article “How to Recognize, Treat Body Dysmorphic Disorder.”