A Prospective Study of Risk Factors for Nonadherence With Antipsychotic Medication in the Treatment of Schizophrenia
J Clin Psychiatry 2006;67(7):1114-1123
© Copyright 2015 Physicians Postgraduate Press, Inc.
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Objectives: This study aimed to
prospectively identify the best single predictor and the best
set of predictors of risk for nonadherence with
antipsychotic medication in the treatment of
patients with schizophrenia.
Method: We used data from 1579 patients in
a 3-year, prospective, naturalistic,
nonrandomized, multisite study of schizophrenia patients
conducted from July 1997 to September 2003 (U.S. Schizophrenia Care and Assessment
Program). Adherence with any oral antipsychotic
medication was assessed using patient-reported
medication adherence and an indirect adherence
measure based on medical record prescription
information. Patients who reported poor medication
adherence or had a medication possession ratio
< = 80% (percentage of days with prescriptions for
any oral antipsychotic) during the first year after
enrollment were defined as nonadherent (N = 296, 18.8%). Thirty-nine previously reported
potential risk factors of nonadherence with
antipsychotic medication were assessed at enrollment
with valid and reliable measures. Risk factors
represented patient-, environment-, and
treatment-related domains, including
sociodemographics, symptom severity, substance use, threat to
safety of self and others, other illness-related
factors, need for supervision, medication-related
adverse events, and prior medication-utilization patterns.
Results: The best single predictor of
future nonadherence was nonadherence during the 6 months prior to enrollment (odds ratio = 4.1,
95% confidence interval = 3.1 to 5.6, p < .001).
The best set of predictors of nonadherence, ordered
by strength of association, included prior
nonadherence, recent illicit drug use, recent alcohol
use, prior treatment with antidepressants, and
greater patient-reported, medication-related
Conclusion: Nonadherence with
antipsychotic medication is associated with a well-defined
set of risk factors that can be used to identify
patients who are predisposed to poor adherence.