It is not known whether sex and age are risk factors for neuroleptic malignant syndrome (NMS).

To examine sex and age distributions in NMS patients based on a systematic review of the literature.

Estimate the sex-specific relative risk of an NMS diagnosis.

EMBASE and PubMed databases were searched in November 2014 using broad, unrestricted criteria to identify any published observation of NMS. Any physically (online or hard copy) accessible and interpretable (using language translation software) report published from January 1, 1998 through November 1, 2014 was considered for inclusion. Secondary sources (e.g., reviews) were included when primary sources could not be accessed. All cases for which the patient's sex or the sample's sex distribution was provided were included, except for redundant reports and cases in which NMS was not the most likely clinical diagnosis. Sex ratio and age distributions were examined using standard graphical techniques and measures of association.

Twenty-eight independent NMS sex ratio estimates were included. Most sex ratio estimates (75%) indicated male preponderance, with a median of 1.47 (95% CI: 1.20–1.80). NMS incidence peaked at age 20–25 years and declined steadily thereafter; males consistently outnumbered females at all age intervals. Major study limitations are the heterogeneity of case ascertainment procedures and the potential for publication bias.

NMS patients are 50% more likely to be males, and NMS is most likely to occur in young adulthood. Men, and all young adults, appear to be at increased risk for NMS.

The authors have not supplied their declaration of competing interest.