The serotonin syndrome: investigation using the Japanese version of the Serotonin Syndrome Scale

Abstract This preliminary study was performed to investigate the prevalence of the serotonin syndrome in a group of Japanese patients in a clinical setting and to test the reliability and value of the Serotonin Syndrome Scale (SSS) as an assessment tool in a Japanese-language version (JSSS). Twenty-three patients, all being treated with serotonin agonists, gave informed consent to participate. Only one patient fulfilled strict diagnostic criteria of the serotonin syndrome and none of the JSSS scores reached the cutoff point of the SSS. Cronbach's α coefficient for the JSSS was 0.56. All inter-rater reliability coefficients were in the excellent range, and the JSSS had a high stability over time. The mean dose of fluvoxamine in the subgroup with high scores on the JSSS was significantly larger than that in the subgroup with low scores and there was a positive but non-significant correlation between total JSSS scores and doses of fluvoxamine. This preliminary study indicates that (1) a full serotonin syndrome was a rare phenomenon in a group of Japanese patients in a clinical setting and (2) the JSSS is a simple and reliable scale for evaluating the serotonin syndrome.