• neuroleptic malignant syndrome;
  • risk factors;
  • psychomotor agitation;
  • mental retardation;
  • dose–response relationship;
  • drug

Objective: To determine whether environmental temperature, agitation, neuroleptic use, mental retardation, and affective disorders were risk factors for neuroleptic malignant syndrome (NMS).

Method: Cases and age- and sex-matched psychiatric controls admitted to a regional acute psychiatric unit over a 10-year period.

Results: Both uni- and multivariate analysis revealed statistically significant differences between patients with NMS (n=15) and controls (n=45) with regard to the presence of mental retardation, psychomotor agitation, and a number of variables relating to neuroleptic use (newly introduced or increased, intramuscular administration, and dosage). We found no differences between NMS patients and psychiatric controls in respect of changes in environmental temperature.

Conclusion: Our study supports the need for caution when using intramuscularly administered, abruptly increasing, high-dose neuroleptics, particularly in mentally retarded or agitated patients, regardless of environmental temperature.