Delirium in psychiatric inpatients: a case-control study.
OBJECTIVE: To investigate the clinical and pharmacoepidemiological determinants of delirium in a psychiatric inpatient population. METHOD: A case-control study design was used. Potential cases and potential controls were identified using hospital discharge data. The clinical record of each subject was reviewed using a validated protocol to confirm case and control status. Subsequently, exposure data were recorded from clinical records. RESULTS: Subjects admitted to hospital with delirium tended to be older, to have pre-existing cognitive deficits, and to have diagnoses of substance use disorders. Subjects who developed delirium after their admission to hospital were older than control subjects, more likely to have a history of cognitive impairment, and were significantly more likely to be treated during the hospitalization with lithium or anticholinergic antiparkinsonian medications. Antipsychotic medication exposures were also associated with delirium, but only at standard or above-standard dosage levels. Antidepressant and sedative-hypnotic medications were not associated with delirium. CONCLUSIONS: These findings indicate that using conservative dosages of antipsychotic medications and minimizing the use of anticholinergic medications for parkinsonian symptoms may help to prevent delirium in psychiatric inpatients. Anticonvulsant mood stabilizers may convey less delirium risk than lithium. Antidepressant medications and sedative-hypnotics were not important determinants of delirium in this population.