While we observed shortfalls in bipolar disorder treatment quality independent of race/ethnicity (at best, no more than 60% of the person-quarters included any antimanic medication between fiscal-years 1997 and 2004), we also observed racial/ethnic disparities in filling prescriptions for antimanic medications. As in prior research, compared to whites, we found disparities for blacks, and unlike most prior literature, no statistically significant disparities for Hispanics.1, 2, 6, 9, 31–34
We found no change in the trends in disparities over time, however. Prior research on changing trends in mental health treatment disparities has been mixed, with some studies indicating no change in the black-white disparities trends when they exist at baseline2, 6, 31
and others showing Hispanic-white disparities worsening over time.2, 6, 31
We found limited evidence of the substitution of antispychotics for mood stabilizers, although less so for blacks.
We found statistically significant disparities for blacks but not Hispanics. Several possible explanations may account for our results. First, clinical characteristics unobservable in claims may account for our findings: blacks with bipolar disorder may be more likely to experience psychosis and have more manic episodes33, 35
compared to whites, whereas Hispanics and whites may be similar regarding these characteristics.33
However, this would not explain why we found blacks were less likely to utilize mood stabilizers but similarly likely to use antipsychotic monotherapy, compared to whites. Alternatively, there may be regional differences in access to higher quality mental health care or in training of clinicians.
Finally, it is possible that observed racial/ethnic differences reflect patient choice.36, 37
Two-thirds to three-quarters of these patients received an antimanic agent at some point over our study period (). When contrasted with the adjusted quarter-level results, this suggests that higher proportions of patients filled antimanic medication prescriptions at some point than remained on them—raising the possibility of racial/ethnic differences in adherence to treatment recommendations. However, while there is evidence of racial/ethnic disparities in psychotropic adherence, the literature overall suggests that when there were differences, it was Hispanics, not blacks, who were less likely to be adherent than whites. Also, that racial/ethnic differences were associated with differential barriers to quality care.38
Thus differential adherence among racial/ethnic groups does not preclude problems in treatment quality.
Independent of race/ethnicity we observed cohort differences in any antimanic, and specific type of antimanic, prescription fill trends over time. Possibly, this is because we observed the 1997 cohort for eight years and the 2000 cohort for only four. Perhaps, the different trajectories represent differences related to longer periods of clinical follow-up; longer follow up may be associated with increased antimanic medication use. Or, these cohort differences may represent secular time or cohort trends.
Our results differ from Depp et al. 15
There are several possible explanations for this, some of which may be due to differences in definitions and methods described earlier. Further, both studies broadly defined racial/ethnic minorities as —black or —Hispanic, combining American-born blacks with those of Caribbean descent, and —Hispanics of Cuban descent with Puerto Ricans and other Hispanics. Although we cannot disaggregate these subgroups in administrative data, treatment patterns differ in some cases across these subgroups.39, 40
San Diego and Florida likely have different compositions of minority subgroups, which also could account for the observed different prescription patterns.
There are several limitations worth noting. Diagnosis and race/ethnicity were ascertained through claims data. However, while the gold standard for diagnostic accuracy are structured clinical interviews or chart review, claims data have demonstrated validity for identifying patients with bipolar disorder.19
Also, while some have raised concerns about the accuracy of administrative data in conducting analyses on race and ethnicity, misclassification in administrative data does not seem to appreciably bias estimates of racial/ethnic treatment utilization for blacks, whites and Hispanics (even when examined in the Florida Medicaid program)24, 41, 42
and therefore are reasonable to utilize when measuring treatment disparities.8
However, an additional limitation of this study (indeed all Medicaid claims studies examining disparities that predate 1999 when the SSA corrected their race/ethnicity data categories), is that prior to 1999, Hispanics who entered this Medicaid program through the SSA, were classified as “Other”. We have accounted for this in the analysis by separating the population into cohorts, determined by the year an individual enrollee entered the bipolar cohort, and by selecting a cohort year after 1999 to highlight in the analyses. Notably, there were no differences in Hispanic-white disparity trends in any of the cohorts (as evidenced by the time trends analyses)—either before or after the year in which the SSA changed their racial/ethnic categories.
While we found overall quality problems independent of race/ethnicity, we also found racial/ethnic disparities—particularly for blacks. From a research and policy perspective, disaggregating the contributing factors for disparities in antimanic medication utilization is an important next step in improving overall bipolar disorder treatment quality, as well eliminating disparities. Clearly, clinical and policy efforts are needed to improve overall pharmacotherapy quality for bipolar disorder. Some evidence suggests that improving overall quality can disproportionately improve care for racial/ethnic minorities11
. Further, targeted efforts may be needed to improve pharmacotherapy for black patients in this population.