Poor adherence with antipsychotic

Assertive Community Treatment in Veterans Affairs Settings: Impact on Adherence to Antipsychotic Medication Marcia Valenstein, M.D., M.S. John F. McCarthy, Ph.D. Dara Ganoczy, M.P.H. Nicholas W. Bowersox, Ph.D. Lisa B. Dixon, M.D., M.P.H. Richard Miller, M.D. Stephanie Visnic, B.A. Eric P. Slade, Ph.D. Objectives: Assertive community treatment (ACT) programs may improve patients outcomes, in part by increasing adherence to antipsychotic medication. This study assessed the association between ACT enrollment and subsequent antipsychotic adherence. Methods: The authors identified a national sample of 763 Veterans Affairs (VA) patients with schizophrenia who were newly enrolled in ACT in fiscal years 2001to2004andhadvalidantipsychotic medication possession ratios (MPRs) for five sequential six-month periods, the first occurring before ACT enrollment. Propensity scores were used to match ACT patients 1:1 with eligible veterans who did not initiate ACT. Logistic regression analyses and generalized estimating equations (GEE) were used to assess the association between ACT enrollment and subsequent antipsychotic adherence. Antipsychotic adherence was compared among ACT enrollees with high, partial, or no participation in ACT services. Results: Before the index date, there was no significant difference in rates of good adherence (MPR.8) among subsequent ACT enrollees (72%) and patients in the control group (70%). However, in each of the four periods after enrollment, ACT enrollees were more likely to have MPRs.8.InGEEanalyses,ACTenrollment was associated with 2.3 greater odds of MPRs.8 (95% confidence interval=1.9 2.7). Among ACT enrollees, higher levels of participation were associated with MPRs.8. Conclusions: In this large, national study, ACT enrollment was associated with higher levels of antipsychotic adherence among VA patients with schizophrenia. This association persisted over time and was greatest among those with higher levels of ACT use. (Psychiatric Services 64:445 451, 2013; doi: 10.1176/appi.ps.201100543) Dr. Valenstein, Dr. McCarthy, Ms. Ganoczy, Dr. Bowersox, and Ms. Visnic are affiliated with the U.S. Department of Veterans Affairs Health Services Research and Development Service and the Serious Mental Illness Treatment, Resource and Evaluation Center, University of Michigan North Campus Research Complex, Building 16, Ann Arbor, MI 48109 (e-mail: marciav@umich.edu). Dr. Valenstein, Dr. McCarthy, and Dr. Bowersox are also with the Department of Psychiatry, University of Michigan Medical School, Ann Arbor, where Dr. Miller was formerly affiliated. Dr. Miller is currently with Our Lady of Fatima Hospital, North Providence, Rhode Island. Dr. Dixon is with the Department of Psychiatry, Columbia University, and with the Center for Practice Innovations, New York State Psychiatric Institute, both in New York City. Dr. Slade is with the Department of Psychiatry, University of Maryland School of Medicine, Baltimore. Poor adherence with antipsychotic medication is common among patients with schizophrenia and is associated with increased risk of psychiatric hospitalization. A structured review of studies assessing antipsychotic adherence among patients with schizophrenia in a variety of settings found that approximately 40% of patients were not fully adherent with antipsychotic medications (1). Data from the U.S. Department of Veterans Affairs (VA) indicated that over a 12- month period, approximately 40% of VA patients with schizophrenia filled less than 80% of the medication supplies needed to take antipsychotics in the doses prescribed (2). Furthermore, over a four-year period, 60% of VA patients with schizophrenia had at least one year in which they filled less than 80% of the supplies needed to take their antipsychotic in the doses prescribed (3). Several large observational studies indicated that patients with poor adherence have 1.4 to 3.9 greater odds of psychiatric hospitalization than patients with good adherence, depending on the time frame used for defining poor adherence (2,4 7). Given that in the VA, fully 18% to 25% of all patients with a diagnosis of schizophrenia are hospitalized each year (8,9), interventions that increase adherence may be important for improving symptoms and for reducing risks of hospitalization. PSYCHIATRIC SERVICES ' ps.psychiatryonline.org ' May 2013 Vol. 64 No. 5 445

The impact of a variety of intervention approaches on antipsychotic medication adherence has been assessed (10 12), but only a few approaches have demonstrated improvements in both adherence and outcomes. Interventions that have behavioral components, focus on problem solving, and target specific adherence behaviors may be more likely to be successful (10). Assertive community treatment (ACT), called mental health intensive case management in the VA health system, is a complex set of services designed to reduce inpatient use among individuals with serious mental illness (13). ACT may affect inpatient use, in part, through improving adherence. ACT emphasizes a team-based approach, a low patient-to-staff ratio, individualized services, and frequent contacts between patients and staff in the community (13). ACT teams accept full responsibility for addressing their clients health care, emphasize the importance of medication adherence, and often provide practical assistance for medication management. Some teams may facilitate fills and deliver medications to patients, although this practice likely would not continue without interruption if staff regularly assessed adherence and found nonadherence or partial adherence and extra medication stored. Most, although not all, studies indicate that ACT decreases use of inpatient services among individuals with serious mental illness, particularly if inpatient use is high before ACT enrollment (14 17). However, the mechanisms underlying ACT s impact on rehospitalization are less clear, including whether changes in adherence associated with ACT enrollment may be important in reducing hospital use. To date, the literature regarding ACT s impact on antipsychotic adherence is mixed, although modestly promising (10). The studies that have examined the relationship between ACT enrollment and medication adherence usually have been small (,100 participants), have examined selected subpopulations (such as patients enrolled in randomized controlled trials that assess another primary outcome or patients with specific comorbidities), have not specified how adherence was measured, or have used subjective adherence measures, such as clinician or patient reports (10,18,19). This study built upon prior work by using national VA administrative data (including pharmacy fill data) to compare medication adherence for a large, comprehensive sample of VA patients with schizophrenia who enrolled in usual-care ACT programs or were eligible but did not enroll. Pharmacy data were used to construct a well-defined and validated measure of adherence, the medication possession ratio (MPR), and adherence was assessed at multiple points over an extended period (24 months). Among ACT enrollees, the level of program participation and adherence were examined. Finally, exploratory analyses examined the relationship between antipsychotic medication adherence in the first year after the study entry date and the number of inpatient psychiatric admissions in the second year. Methods The study was approved by the human subjects committees at the Veterans Health Administration medical centers in Ann Arbor, Michigan, and Baltimore. Data sources Study data were obtained from the VA National Psychosis Registry (NPR), which is developed and maintained by the VA Serious Mental Illness Treatment Resource and Evaluation Center in Ann Arbor, Michigan. The NPR includes national VA health system records for all VA patients with diagnoses of schizophrenia, bipolar disorder, and other psychoses. Study participants Using the VA ACT programs enrollment registry and data from the VA NPR, we identified all 763 VA patients newly enrolling in ACT between fiscal years 2001 and 2004 (October 1, 2000 September 30, 2004) who had a diagnosis of schizophrenia in the 12 months before enrollment, were alive for 12 months after enrollment, met VA-defined criteria for high hospital use (three or more mental health inpatient admissions or 30 or more mental health inpatient days in the prior 12 months) (20), lived within 60 miles of a VA ACT team (the usual operating area of VA ACT teams), and had 90 or more outpatient days in each of five sequential six-month periods of interest (zero to six months before the date of ACT entry or index date for the control group and zero to six, seven to 12,13to18,and19to24monthsafter ACT entry date or the index date). To have MPRs calculated during these study periods, patients needed to have had an antipsychotic fill six to 12 months before ACT entry or the index date and also to have had 90 or more outpatient days in each six-month period. Propensity scores for the probability of enrolling in ACT were used to match ACT enrollees 1:1 with patients who met all of the same inclusion criteria but did not enter an ACT program. Propensity scores were calculated on the basis of adherence at baseline, age, sex, race, marital status, homelessness, substance use disorder diagnosis, Charlson comorbidity score, number of inpatient psychiatric stays in the past year, number of inpatient psychiatric days in the past year, service connection, number of domiciliary days in the past year, number of residential rehabilitation days in the past year, number of mental health visits in the past year, number of substance abuse visits in the past year, and the Veterans Integrated Service Network (VISN) in which the patient received care. Propensity score matching is often used to balance between-group differences in the distribution of the key covariates, allowing matching on multiple factors (21). Measure of antipsychotic medication adherence As in prior studies, data on the days supply of antipsychotic medication dispensed during each six-month study period were used to calculate MPRs. The MPR is defined as the number of days supply of antipsychotic received from an outpatient pharmacy divided by the number of days supply needed for continuous outpatient antipsychotic use. For each period, MPRs were calculated by adding the number of days supply of antipsychotic medication dispensed by the outpatient pharmacy during the six-month period plus any remaining days supply from fills in 446 PSYCHIATRIC SERVICES ' ps.psychiatryonline.org ' May 2013 Vol. 64 No. 5

the prior six months that would have covered days during the period of interest. Medications received at the time of discharge from inpatient settings were included in outpatient pharmacy supplies. Days that patients spent in institutional settings (VA hospitals or nursing homes) were subtracted from the outpatient days supply needed. MPRs calculated from VA pharmacy data have been shown to correlate with important intermediate patient outcomes, including psychiatric admission of patients with schizophrenia to VA facilities and other health care settings (2,22). Covariates Data for all covariates were obtained from administrative data in the VA NPR. Measures included patients demographic data (age, sex, race, and marital status). Other covariates were constructed from data from the 12 months before the index date, including an indicator for homelessness (ICD-9 code V60.0 or services utilization in specific clinics or bed sections ) (23), number of psychiatric inpatient days, number of psychiatric inpatient admissions, number of antipsychotics prescribed, and a substance use disorder diagnosis (ICD-9 codes 291.X, 292.X, 303.0, 303.9 305.0, and 305.2 305.9 without a fifth digit of 3 to signify remission). A modified version of the Charlson Comorbidity Index indicating the presence of 19 medical diagnoses in the year before the index date was included as a measure of medical comorbidity (24). For an exploratory analysis of the level of ACT participation among enrollees and medication adherence, we constructed a variable for full and partial ACT participation. Level of participation was measured by the frequency of contact between the ACT team and the client. Patients who completed at least 42 ACT visits in a 12-month period were considered to be fully participating in ACT treatment, whereas patients who completed 41 visits or fewer in a 12- month period were considered to be partially participating in ACT care. This represents a relatively conservative estimate for full ACT involvement. VA criteria for ACT programs indicate that ACT usually involves two Table 1 Characteristics of patients enrolled or not enrolled in assertive community treatment (ACT) Total (N=1,526) or three contacts per week, with lower levels of contact only after a year of treatment. VA health system regulations also specify that VA ACT programs must have at least 41 contacts per client per year to qualify for a higher-than-normal budgetary allowance for these patients (25). Data analyses Univariate analyses of patient characteristics and good adherence (MPR $.8) at various points were described by means and frequencies. Bivariate analyses assessing the relationship between good adherence and ACT enrollment were completed by using chi square statistics. To assess differences in rates of good antipsychotic adherence among patients who entered or did not enter ACT, we used a generalized linear model with ACT Non-ACT Characteristic N % N % N % p Male 1,361 89 690 90 671 88.117 Female 165 11 73 10 92 12 Age (mean6sd) 50.269.7 50.268.8 50.2610.4.279 Race-ethnicity White 868 57 440 58 428 56.870 Black 530 35 263 35 267 35 Hispanic 79 5 39 5 40 5 Other 11 1 5 1 6 1 Unknown 38 3 16 2 22 3 Marital status Divorced 452 30 223 29 229 30.941 Married 195 13 96 13 99 13 Never married 719 47 362 47 357 47 Separated 119 8 59 8 60 8 Widowed 41 3 23 3 18 2 Homeless in past year 340 22 179 24 161 21.268 Substance abuse 662 43 343 45 319 42.215 CCI score a 0 857 56 420 55 437 57.605 1 488 32 253 33 235 31.1 181 12 90 12 91 12 Inpatient psychiatric admissions in past year (mean6sd) 2.862 2.862 2.8 2.355 Inpatient psychiatric days in past year (mean6sd) 51.8639.3 53.1642.3 50.6636.0.102 MPR at baseline (mean6sd) b.816.29.836.28.806.30.111 a A modified version of the Charlson Comorbidity Index (CCI) indicating the presence of 19 medical diagnoses in the year before study enrollment b Medication possession ratios $.80 indicate good adherence. logit link and a generalized estimating equation (GEE) method. These analyses adjusted for patient demographic variables, baseline adherence, homelessness, substance use diagnosis, medical comorbidity score, number of antipsychotics prescribed, and prior inpatient utilization. GEE analyses more appropriately estimate regression coefficients and variance when correlated data are used (26). We used a GEE approach because adherence observations were nested within patients over the two-and-one-half years of the study. In exploratory analyses, we used chi square statistics to explore whether patients who enrolled in ACT showed significant differences in medication adherence by level of participation in ACT. We used GEEs to assess whether adherence (MPR) in the first PSYCHIATRIC SERVICES ' ps.psychiatryonline.org ' May 2013 Vol. 64 No. 5 447

Table 2 Patients enrolled or not enrolled in assertive community treatment (ACT) with good adherence to antipsychotic medication, by study period a Total (N=1,526) year after the index date predicted inpatient admissions in the second year after the index date. A mixed-effects model was used to account for correlation of inpatient days within patient. Statistical analyses were completed by using SAS software, version 9.2. Results Patient sample Table 1 shows the characteristics of ACT enrollees and ACT-eligible ACT Non-ACT Study period N % N % N % p 6 months before ACT entry or index date 1,082 71 549 72 533 70.367 After ACT entry 0 6 months 1,072 70 617 81 455 60,.001 7 12 months 1,019 67 580 76 439 58,.001 13 18 months 993 65 559 73 434 57,.001 19 24 months 965 63 553 73 412 54,.001 a Medication possession ratios $.8 indicated good adherence. nonenrollees after propensity score matching. After propensity matching, there were no significant group differences across any covariates that might be associated with both adherence and with ACT enrollment. The study sample (N=1,526) was predominantly male (89%) and older, with a mean6sd age of 50610 years. Most patients were white (57%), but black patients constituted a substantial minority (35%). Approximately 22% of patients had an indicator for homelessness in the year before the index date, and 43% had a concurrent substance use diagnosis. Medication adherence by ACT enrollment In the six months before the study index date, there were no differences in adherence (MPR $.8) among patients who enrolled (72%) or did not enroll (70%) in ACT. However, in all six-month periods that followed the index date, the percentage of patients with MPRs $.8 was higher among ACT enrollees than among nonenrollees, both in unadjusted (Table 2) and adjusted analyses (Table 3). In multivariate logistic regression analyses, the odds of good adherence among ACT enrollees were greatest in the six-month period immediately following enrollment. However, the odds of good adherence were twice as high or higher among ACT enrollees versus nonenrollees across all periods following enrollment. After adjustment for demographic and clinical variables, GEE analyses Table 3 Association of good adherence with medication and enrollment in assertive community treatment (ACT), by patient characteristic and study period a 0 6 months 7 12 months 13 18 months 19 24 months Characteristic OR 95% CI OR 95% CI OR 95% CI OR 95% CI ACT (reference: no) 2.97 2.25 3.92 2.27 1.77 2.92 2.00 1.55 2.59 2.11 1.63 2.74 Baseline MPR $.8 (reference:,.8) 4.69 3.58 6.15 3.94 3.01 5.15 2.98 2.28 3.90 2.23 1.70 2.92 Age.99.97 1.00 1.00.99 1.02 1.01.99 1.02 1.01 1.00 1.03 Male (reference: female).90.57 1.42 1.11.72 1.70.74.49 1.10.81.53 1.24 Race-ethnicity (reference: white) Black.64.48.84.75.58.98.53.40.69.47.36.62 Hispanic.87.49 1.53 1.25.66 2.36 1.92.99 3.73 1.29.74 2.25 Other 1.23.31 4.83.14.03.63.26.08.87.62.22 1.80 Unknown.94.40 2.18.47.21 1.06.77.40 1.51.67.30 1.51 Marital status (reference: married) Divorced.88.57 1.36 1.02.66 1.58 1.37.90 2.11 1.20.79 1.81 Never married.96.62 1.48 1.11.74 1.67 1.56 1.03 2.35 1.30.89 1.90 Separated.66.37 1.18.85.49 1.47.86.50 1.49.78.44 1.38 Widowed 3.25 1.16 9.07.83.30 2.24 1.92.80 4.58 2.07.84 5.05 Homeless (reference: no) 1.07.78 1.48.84.62 1.15.70.51.97.78.57 1.08 Substance abuse (reference: no).77.57 1.02.90.68 1.18.80.61 1.07.91.69 1.21 CCI score (reference: 0) b.1 1.76 1.11 2.80 1.07.70 1.64 1.08.71 1.66.91.60 1.40 1 1.02.77 1.35.90.68 1.20.89.67 1.19.87.65 1.16 Inpatient psychiatric admissions.84.77.90.88.82.95.91.84.99.89.81.98 Inpatient psychiatric days 1.00 1.00 1.01 1.01 1.00 1.01 1.00 1.00 1.01 1.01 1.00 1.01 Number of antipsychotics 2.85 2.30 3.54 3.40 2.63 4.40 4.54 3.44 5.99 5.67 4.36 7.38 a Good adherence was indicated by medication possession ratios (MPR) $.8. b A modified version of the Charlson Comorbidity Index (CCI) indicating the presence of 19 medical diagnoses in the year before study enrollment 448 PSYCHIATRIC SERVICES ' ps.psychiatryonline.org ' May 2013 Vol. 64 No. 5

that examined the impact of ACT enrollment over time indicated that ACT enrollees were 2.3 times more likely than nonenrollees to have good antipsychotic adherence (Table 4). ACT participation and adherence As outlined in Table 5, ACT enrollees who received higher levels of ACT services were more likely to have MPRs $.8. Between seven and 24 months postenrollment, approximately 80% of patients who averaged 42 or more ACT visits in a year had MPRs $.8, compared with 55% to 70% of patients with fewer ACT visits. Only 31% to 42% of patients who discontinued ACT involvement entirely in the second year had good antipsychotic adherence in that year. Adherence and psychiatric inpatient days An exploratory analysis of the study sample indicated that adherence in the first year was not significantly related to the number of inpatient admissions in the second year after enrollment. Only the number of inpatient stays, substance use, patient age, and the number of antipsychotics prescribed in the first year were significantly associated with the number of inpatient stays in the second year after enrollment. [A table presenting the results of this mixed model is available online as a data supplement to this article.] Discussion This study of propensity-matched patients who enrolled or did not enroll in ACT is the largest effort, to date, to assess the relationship between ACT enrollment and subsequent antipsychotic adherence among patients with schizophrenia. Study results indicated that ACT enrollment is strongly associated with the likelihood of good antipsychotic adherence (MPR $.8). Furthermore, the association between ACT enrollment and adherence persisted over a 24-month period. Last, among patients who were enrolled in ACT, higher use of ACT services was associated with higher levels of adherence. The latter association may be due to a participation-related salutary impact of ACT on adherence or to a third factor that influenced Table 4 Association of good adherence with medication and enrollment in ACT over time, by patient characteristic a Characteristic OR 95% CI ACT (reference: no) 2.26 1.90 2.69 Baseline MPR $.8 (reference:,.8) 3.28 2.72 3.95 Study period.94.89 1.00 Age 1.00.99 1.01 Male (reference: female).88.66 1.17 Race-ethnicity (reference: white) Black.59.49.72 Hispanic 1.29.87 1.91 Other.39.24.63 Unknown.68.44 1.05 Marital status (reference: married) Divorced 1.09.81 1.47 Never married 1.20.91 1.60 Separated.78.53 1.15 Widowed 1.69.82 3.47 Homeless (reference: no).84.68 1.03 Substance abuse (reference: no).85.70 1.03 CCI score (reference: 0).1 1.15.86 1.54 1.92.75 1.12 Inpatient psychiatric admissions.88.83.93 Inpatient psychiatric days 1.00 1.00 1.01 Number of antipsychotics 3.95 3.39 4.60 a ACT, assertive community treatment. Medication possession ratios (MPRs) $.8 indicate good adherence. both receipt of ACT services and adherence. However, taken together, the findings suggested that ACT and other similar intensive case management models may improve medication adherence. The results of this study were congruent with most, although not all, prior studies examining adherence after ACT enrollment (10,18,19) and add to the growing literature that suggests that ACT may have a strong and lasting impact on antipsychotic medication adherence. Although the primary study analyses indicated that ACT enrollment was associated with increased likelihood of MPRs $.8, the exploratory analysis examining the relationship between antipsychotic adherence in Table 5 Engagement in ACT services among patients with good medication adherence, by study period a Total No ACT visits b Partial engagement c Full engagement d Study period N % N % N % N % p 0 6 months 617 81 0 98 78 519 82.335 7 12 months 580 76 0 69 55 511 80,.001 13 18 months 559 73 19 31 130 70 410 80,.001 19 24 months 553 73 26 42 121 65 406 79,.001 a A total of 763 patients were enrolled in assertive community treatment (ACT). Good adherence was indicated by medication possession ratios $.8. b A total of 62 patients had no visits between 13 and 24 months. c Partial engagement was defined as,42 visits over a 12-month period (N=126, 0 12 months; N=187, 13 24 months). d Full engagement was defined as $42 visits over a 12-month period (N=637, 0 12 months; N=514, 13 24 months). PSYCHIATRIC SERVICES ' ps.psychiatryonline.org ' May 2013 Vol. 64 No. 5 449

the first year after enrollment and inpatient admissions in the second year after enrollment did not show the expected association between increased adherence and decreased admissions. Interventions that improve antipsychotic adherence have not always been associated with reduced hospitalization (11,12). A prior study found that after entering ACT, homeless patients had improved adherence and improved symptoms but no changes in inpatient readmission (18). In this study, patients who enrolled in ACT had approximately 20% more days with adequate medications on hand. This increment may not have been sufficient to have a differential impact on the number of inpatient days. ACT staff may also have facilitated hospitalization of enrolled patients at earlier stages of decompensation, appropriately reducing risks of harm to self or others during unstable periods or diverting patients from judicial or other nonmedical institutional settings. In a related study, ACT enrollment has been found to be associated with reduced medical costs but to have a complex relationship with hospitalization, including no change in the number of hospital stays but fewer number of hospital days and increased use of partial hospitalization. Cost benefits were strongly influenced by the level of patient hospital use before ACT enrollment (27). Several caveats should be considered when interpreting the study findings. First, although we matched ACT-enrolled patients with ACTeligible but nonenrolled patients by using propensity scores, these scores use only measured variables. Unobserved variables may remain unbalanced between the two groups and contribute to the differences observed in adherence. Our sample was constituted from ACT patients and a matched control group who had to have at least 90 outpatient days in five consecutive six-month periods. As a result, study patients may have been somewhat healthier than other ACT patients. Improvements in adherence and associations between adherence and hospital stays may have been more robust among patients with very high levels of hospital use. MPRs are also imperfect measures of adherence. Patients might fill their antipsychotic medications outside the VA system, and their low MPRs might inaccurately suggest poor adherence. Conversely, patients might refill their prescriptions, have high MPRs, but fail to ingest their medications. Potentially, these measurement issues may have differed for patients who were enrolled or not enrolled in ACT. For example, ACT patients may have been more likely than individuals in the matched control group to receive refills but not use the medications if ACT staff were more successful in their efforts to facilitate refills than to facilitate regular ingestion. Conclusions This is the largest study, to date, to examine the relationship between ACT enrollment and subsequent antipsychotic adherence among patients with schizophrenia treated in clinical settings. Patients adherence was assessed by using an objective, validated, but unobtrusive measure the MPR. We found that ACT enrollment was strongly associated with adherence to antipsychotic medication as measured by the MPR. This association persisted for at least 24 months. Furthermore, ACT patients with higher levels of participation had higher levels of adherence. These findings add to the growing literature suggesting that ACT has a strong and long-lasting impact on antipsychotic medication adherence. However, additional studies are needed to assess the degree to which improvements in adherence that are due to ACT services affect subsequent rehospitalization or inpatient lengths of stay. Acknowledgments and disclosures This study was funded by a grant (IIR-06-115) to Dr. Slade from the Health Services Research and Development Service, U.S. Department of Veterans Affairs. The authors report no competing interests. References 1. Lacro JP, Dunn LB, Dolder CR, et al: Prevalence of and risk factors for medication nonadherence in patients with schizophrenia: a comprehensive review of recent literature. Journal of Clinical Psychiatry 63:892 909, 2002 2. Valenstein M, Copeland LA, Blow FC, et al: Pharmacy data identify poorly adherent patients with schizophrenia at increased risk for admission. Medical Care 40:630 639, 2002 3. Valenstein M, Ganoczy D, McCarthy JF, et al: Antipsychotic adherence over time among patients receiving treatment for schizophrenia: a retrospective review. Journal of Clinical Psychiatry 67:1542 1550, 2006 4. Weiden PJ, Kozma C, Grogg A, et al: Partial compliance and risk of rehospitalization among California Medicaid patients with schizophrenia. 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