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Psychotropic Medication Nonadherence Among United States Latinos: A Comprehensive Literature Review

2009; American Psychiatric Association; Volume: 60; Issue: 2 Linguagem: Inglês

10.1176/ps.2009.60.2.157

1557-9700

Nicole M. Lanouette, David P. Folsom, A. Sciolla, Dilip V. Jeste,

Stuttering Research and Treatment

Back to table of contents Previous article Next article ArticleFull AccessPsychotropic Medication Nonadherence Among United States Latinos: A Comprehensive Literature ReviewNicole M. Lanouette M.D.David P. Folsom M.D., M.P.H.Andres Sciolla M.D.Dilip V. Jeste M.D.Nicole M. Lanouette M.D.David P. Folsom M.D., M.P.H.Andres Sciolla M.D.Dilip V. Jeste M.D.Published Online:13 Jan 2015https://doi.org/10.1176/ps.2009.60.2.157AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail Medication nonadherence among patients with psychiatric disorders, such as schizophrenia, bipolar disorder, and depression, is a major barrier to favorable treatment outcomes. Suboptimal adherence to psychotropic medications for these disorders has been associated with relapse, significantly more psychiatric hospitalizations and emergency room visits, poorer mental functioning, lower life satisfaction, more disability-related absences from work, greater substance use, increased suicidal behavior, poorer adherence to medications for comorbid medical conditions, and higher health care costs ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ). Unfortunately, nonadherence to antipsychotics, antidepressants, and mood stabilizers is common; previous literature reviews have noted rates ranging from 10% to 77%, with mean rates of 35%–60% ( 17 , 18 , 19 , 20 ). Previous studies have established risk factors for nonadherence, including limited insight, a negative attitude or subjective response toward medication, a shorter duration of illness, comorbid substance abuse, a poor therapeutic alliance, living alone, more self-reported side effects, and limited family support ( 18 , 19 , 20 ). However, many previous studies were significantly limited because they were conducted with predominantly Euro-American populations. Ethnic and racial disparities in adherence have been noted; nonwhite patients have been found to be more likely to have lower adherence ( 3 , 21 , 22 , 23 ). Latinos are the largest and most rapidly growing minority group in the United States, constituting just over 13% of the population ( 24 ). More than 40% are foreign-born, and 75% are immigrants or children of immigrants ( 25 ). Acculturation, "the process by which individuals adopt the attitudes, values, customs, beliefs, and behaviors of another culture" ( 26 ), has been found to have mixed health effects for Latinos, including mental health effects ( 27 , 28 , 29 ). Prevalence rates of psychiatric disorders are lower among Latinos who are less acculturated, but those who have a disorder are less likely to receive mental health treatment ( 30 , 31 ). Given these health and acculturation relationships, acculturation could potentially affect adherence via, for example, physician-patient communication or health literacy. Ethnic differences have been previously noted for Latinos in the number and use of prescriptions for psychotropics ( 32 , 33 ), psychotropic dosing needs ( 34 ), response to psychotropics ( 35 ), and their tolerability for Latinos ( 36 , 37 ). However, to our knowledge, there has not yet been a comprehensive review of the literature examining psychotropic adherence among Latinos living in the United States that includes the frequency of nonadherence, factors associated with it, and influences of language and acculturation on nonadherence. Our objectives were to assess the rate of nonadherence to psychotropic medications among Latinos living in the United States, compare the rate with those for other ethnic minority groups and Euro-Americans, and identify any culturally relevant factors that influence adherence among Latinos.MethodsData sources We searched MEDLINE and PsycINFO databases using combinations of the following keywords: antipsychotic, mood stabilizer, antidepressant, lithium, neuroleptic, psychotropic, schizophrenia, bipolar disorder, depression, adherence, compliance, Latino, Hispanic, ethnicity, Spanish language, and acculturation. We searched for articles published since 1980 that reported studies that measured prevalence of adherence to antipsychotics, antidepressants, or mood stabilizers among Latino adults in the United States. Reference lists from recent reviews ( 18 , 19 , 20 , 38 , 39 ) were also examined, as were bibliographies from all potentially relevant articles. Study selectionWe identified 518 papers in the searches. One of the authors (NML) then read every title and identified 214 potentially relevant articles. During this screening, broad inclusion criteria were used, but we excluded studies that examined adherence among patients who had only nonpsychiatric illnesses or that focused on nonpsychiatric medications only (for example, adherence to highly active antiretroviral therapy in HIV-AIDS). Also excluded were articles not in English or Spanish and articles that reported studies of pediatric populations only or studies conducted outside the United States. A search of the Spanish-language literature revealed no potentially relevant studies because all were conducted with populations outside the United States.The 214 potentially relevant articles were read in detail by one of the authors. To be included, studies had to be of U.S. populations (including people living in Puerto Rico, although no studies of psychotropic medication adherence included this population), had to be in English or Spanish (no studies were in Spanish), had to include Latinos, and had to measure adherence and nonadherence (including self-report and medication discontinuation rates) to antidepressants, antipsychotics, or mood stabilizers prescribed for depression, schizophrenia, schizoaffective disorder, or bipolar disorder (even if adherence was not the primary focus of the study). Studies also had to examine ethnicity as a variable related to adherence or report adherence rates of all ethnic groups in the studies (so that we could determine whether there were significant differences between ethnic groups), or for studies that included only Latino participants, the studies had to examine adherence and factors influencing adherence. We excluded studies if they did not measure separate adherence rates for Latinos; included only children and adolescents; examined medication adherence only for medications that were not antidepressants, antipsychotics, or mood stabilizers; and examined adherence to antidepressants, antipsychotics, or mood stabilizers that were prescribed for diseases other than those listed above (for example, we excluded studies of anxiety and dementia). Studies were also excluded if only study dropout rates were reported, rather than medication discontinuation or adherence rates, because many factors that cause study dropout do not necessarily cause nonadherence. This criterion led to our exclusion of a widely cited study that found that Latinos were more likely than Euro-Americans to drop out of a clinical trial and that identified the reasons for study discontinuation ( 36 ). Data extraction Of the 214 initially identified articles, 193 were excluded and 21 were included in our final analysis ( 1 , 6 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ). The results from one study were reported in two different articles ( 52 , 53 ), and we counted the articles as one study. One included study ( 44 ) examined adherence-related factors in a subset of a sample in another study ( 43 ), and we counted these as one study and used the nonadherence rate reported for the larger sample ( 43 ) in our calculation of the mean nonadherence rate for studies including only Latinos. For each of the 21 studies, two authors (NML and DPF) examined the study design and objectives, the location and patient population, medications studied, participant characteristics (including preferred language of participants and providers, if reported), measures of adherence, rates of adherence overall and by race-ethnicity, associations between race-ethnicity and adherence (including statistical measures), and any other adherence-relevant factors identified. For consistency, we use the terms "adherence" and "nonadherence" throughout this review, replacing the terms "compliance" and "noncompliance," which were used in some studies. Calculation of nonadherence rates For standardization, if studies reported adherence rates, we calculated nonadherence rates and report those. Most studies examined only adherence and nonadherence. Therefore, for studies that provided information on additional categories of adherence, such as for persons who were partially adherent or those who were excess fillers (those who filled prescriptions more frequently than expected) ( 6 , 40 , 58 , 59 , 60 ), we report all the rates that were provided ( Table 1 ); however, for mean nonadherence rate calculations, we used the summed partial adherence, nonadherence, and excess filler rates as the nonadherence rate. One article ( 40 ) reported separate adherence rates by ethnicity and diagnosis, and for this article, we give the separate rates ( Table 1 ); however, for calculating mean nonadherence rates, we averaged the nonadherence rates of the patients with different diagnoses within each ethnic group. Table 1 Studies of medication nonadherence in which the sample included U.S. Latinos onlyTable 1 Studies of medication nonadherence in which the sample included U.S. Latinos onlyEnlarge table Although no measure of medication adherence is ideal, some measures have demonstrated more reliability than others. Patient and caregiver reports and physician reports of adherence have been shown to underestimate adherence ( 61 , 62 ), whereas adherence calculated by use of medication event monitoring system (MEMS) caps (electronic bottle caps) and from pharmacy fill records (for example, medication possession ratios [MPRs] and cumulative possession ratios [CPRs]) have been shown to be generally more objective measures ( 3 , 62 ). Therefore, we also separately analyzed the 11 articles that reported studies that used these typically more objective measures ( 1 , 6 , 46 , 48 , 51 , 52 , 54 , 56 , 58 , 59 , 60 ). Data analysis and statistics For studies in which comparison data were available but the investigators did not compare adherence rates of separate racial or ethnic groups, we used chi square tests to test the significance of differences in adherence rates by group. We performed such secondary calculations for 11 studies: nonadherence percentage calculations for three studies ( 51 , 55 , 56 ), chi square tests for two studies ( 50 , 57 ), and both percentage calculations and chi square tests for six studies ( 1 , 40 , 47 , 49 , 58 , 60 ). For the two studies in which the unadjusted and adjusted nonadherence rates yielded conflicting results ( 55 , 56 ), we included both findings but used the results of the multivariate analysis when comparing rates between racial or ethnic groups. We used two methods to compare nonadherence rates between racial or ethnic groups. First, we examined the mean nonadherence rates across studies, which included calculating an effect size of the difference between the rates for Latinos and Euro-Americans. Second, we counted the number of studies that compared rates among groups, and we report how many of the studies did and did not find significant differences. To calculate the effect size, we used SPSS version 12.0.1 to pool the nonweighted nonadherence means and standard deviations across the studies and then used an online effect size calculator ( web.uccs.edu/lbecker/Psy590/escalc3.htm ). We used online chi square calculators ( www.graphpad.com and www.quantpsy.org ) for chi square calculations, and we used SPSS version 12.0.1 for descriptive statistics. Racial and ethnic group terminologyThe terminology for racial and ethnic groups in the literature is highly varied. For the purposes of this review, the term "U.S. Latino" includes anyone residing in the United States, including Puerto Rico, who has Mexican, Central American, South American, Puerto Rican, or Cuban ancestry. We use the terms "African American" to refer to U.S. residents who trace their ancestry to Africa and "Euro-American" for U.S. residents with European ancestry. For studies that used "Hispanic," "black," or "Caucasian," we have replaced these terms with "Latino," "African American," and "Euro-American," respectively, for standardization. If country of origin of the participants was specified in a study, we include that information. We understand that these definitions have limitations in that they group people from highly diverse backgrounds. Very few studies reported separate adherence rates for Asian Americans or other racial or ethnic groups, and the number of Asian-American patients or patients from other groups in those studies was typically very small, so we were unable to compare nonadherence rates or risk factors for Latinos and those groups.ResultsDescription of studies and prevalence of nonadherence The 21 studies ( Tables 1 and 2 ) that met inclusion criteria ( 1 , 6 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ) showed great heterogeneity in terms of study design and objectives and of population studied. Table 1 shows the four investigations that had only Latino participants, and Table 2 shows the 17 studies that included Latinos and other ethnic groups. Table 2 Studies of medication nonadherence in which the sample included U.S. Latinos and other U.S. ethnic groupsTable 2 Studies of medication nonadherence in which the sample included U.S. Latinos and other U.S. ethnic groupsEnlarge table In terms of study design, 13 studies were prospective and eight retrospective. Study objectives varied; some studies focused specifically on adherence ( 1 , 6 , 41 , 44 , 45 , 46 , 47 , 49 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ), and others addressed different questions but measured adherence as part of their procedures. Eight studies were based in California ( 6 , 42 , 43 , 47 , 48 , 50 , 54 , 55 ), two in Texas ( 41 , 51 ), one in New Mexico ( 52 ), one in New York ( 49 ), one in Connecticut ( 56 ), and one in Ohio ( 40 ). Four studies were from National Registries of the Veteran's Health Administration ( 46 , 58 , 59 , 60 ), and three were national studies ( 1 , 45 , 57 ). Twelve studies investigated nonadherence to antipsychotics ( 1 , 6 , 41 , 42 , 43 , 46 , 49 , 50 , 51 , 54 , 58 , 59 ), five examined antidepressants ( 45 , 47 , 52 , 55 , 57 ), two examined mood stabilizers ( 48 , 60 ), and two examined a combination of these medications ( 40 , 56 ). Ten studies focused on schizophrenia or schizoaffective disorder ( 1 , 6 , 41 , 42 , 43 , 49 , 50 , 51 , 59 ), five focused on depression ( 45 , 47 , 52 , 55 , 57 ), three focused on bipolar disorder ( 48 , 58 , 60 ), and three involved a combination of these diagnoses ( 40 , 54 , 56 ). The total sample size in the 21 studies ranged from 40 to 44,637 (mean±SD=6,024±13,268). Of the 17 studies that included both Latinos and other racial or ethnic groups, the percentage of Latino participants ranged from 2.9% to 56% (mean=20.3%±19.5%). Of the seven studies that reported preferred language, the proportion of Spanish-speaking participants ranged from none to 100% (mean=45.7%±35.0%). For seven studies, country of origin or ancestry of Latino participants was reported, which was primarily Mexico in four studies ( 41 , 43 , 50 , 51 ), primarily Puerto Rico in two ( 40 , 56 ), and a mix of Mexico, Guatemala, and El Salvador in one ( 42 ). Studies used a range of adherence measures, including patient report ( 50 , 55 ), chart review or physician report ( 41 ), a combination of patient and family report and chart review ( 43 , 49 ), medication discontinuation (by patient report) ( 45 , 47 , 57 ), pill counts of returned pills ( 46 ), MEMS caps ( 56 ), calculations from pharmacy records (including cumulative mean gap ratio [CMGR], MPR, and CPR) ( 1 , 6 , 48 , 51 , 52 , 58 , 59 , 60 ), and urine testing for metabolites ( 54 ). Two studies did not describe the adherence measure ( 40 , 42 ). Nineteen studies reported the time period during which adherence was examined, which ranged from one week to 48 months (mean=10.2±10.3 months). Nonadherence rates Three of the four studies that included only Latinos ( 41 , 43 , 45 ) ( Table 1 ) reported nonadherence rates, which ranged from 33.0% to 55.0% (mean=44.0%±11.0%). The fourth ( 42 ) explored risk factors for nonadherence among Latinos but did not detail rates, and it is discussed below. Of the 17 studies that included Latinos and other racial or ethnic groups ( Table 2 ), 12 ( 1 , 6 , 40 , 47 , 49 , 50 , 51 , 52 , 56 , 57 , 58 , 60 ) provided data allowing comparison of nonadherence rates between Latinos and Euro-Americans. The mean nonadherence rates for Latinos and Euro-Americans were 39.4%±15.7% and 29.2%±16.5%, respectively, yielding an overall effect size of .64. Ten of these studies also had data available for African Americans ( 1 , 6 , 47 , 49 , 50 , 51 , 56 , 57 , 58 , 60 ), and nonadherence rates in those studies were as follows: Latinos, range of 17.2%–63.1%, (mean=41.0%±16.3%); Euro-Americans, range of 10.0%–57.2% (mean=31.3%±17.2%), and African Americans, range of 22.7%–65.1% (mean=43.2%±16.9%). Only one study reported separate rates by ethnicity and diagnosis ( 40 ); it showed no difference between nonadherence rates for Latinos with schizophrenia compared with Euro-Americans with schizophrenia and a nonsignificant trend (p=.055) toward higher nonadherence rates among Latinos compared with Euro-Americans for patients with depression. Comparison of rates for racial or ethnic groups Sixteen studies evaluated differences in nonadherence rates between Latinos and Euro-Americans. (In addition to the 12 studies that reported nonadherence rates for Latinos and Euro-Americans, four studies measured and compared nonadherence rates in the two groups but did not provide details.) Of these 16 studies, six found no statistically significant differences ( 1 , 40 , 46 , 48 , 49 , 54 ), nine found that Latino patients had significantly higher nonadherence rates ( 6 , 47 , 50 , 51 , 52 , 57 , 58 , 59 , 60 ), and one found that monolingual Spanish-speaking patients, but not bilingual patients, were more likely to be nonadherent than Euro-American patients ( 56 ). In ten of 14 studies, African Americans had significantly greater nonadherence rates than Euro-Americans ( 1 , 6 , 46 , 49 , 51 , 54 , 56 , 58 , 59 , 60 ), whereas four found no difference ( 47 , 48 , 50 , 57 ). Seven of the ten studies that compared rates between Latinos and African Americans found no difference ( 1 , 47 , 49 , 50 , 51 ), and three found that Latinos had lower nonadherence rates ( 54 , 58 , 60 ). More objective measures of adherence Eleven studies ( 1 , 6 , 46 , 48 , 51 , 52 , 54 , 56 , 58 , 59 , 60 ) used MEMS caps, calculations from pharmacy data (including MPRs, CPRs, and CMGRs), or urine testing. None of the studies that included only Latinos used these methods. Six of the 11 studies reported rates by group ( 1 , 6 , 51 , 56 , 58 , 60 ). In these studies the mean nonadherence rate was 43.7%±18.7% for Latinos, 36.5%±18.9% for Euro-Americans, and 49.5%±17.7% for African Americans. Outcomes and factors related to Latino nonadherence Five of the 21 studies ( 41 , 42 , 43 , 44 , 45 , 56 ) included a majority of Latino participants and examined outcomes of and risk and protective factors for nonadherence specifically for Latinos ( Table 3 ). Table 3 Factors potentially related to psychotropic medication adherence among U.S. Latinos and reference numbers of the studies that investigated themTable 3 Factors potentially related to psychotropic medication adherence among U.S. Latinos and reference numbers of the studies that investigated themEnlarge table Only one study ( 56 ) made cross-cultural comparisons of risk factors, investigating the most significant factors for each group. Thus we were unable to answer the question of the relative importance of these identified factors for Latinos compared with other groups, except through comparisons with previously published reviews. Also, there was little overlap between the reports in terms of factors examined. Therefore, direct comparisons of the relative importance of the identified factors were not possible. The one study that made cross-cultural comparisons identified older age among monolingual Spanish-speaking Latinos and more years of previous treatment and fewer depressive symptoms among Euro-Americans as predictors of higher adherence ( 56 ). Nonadherence was found to predict a worse illness course in the two studies that examined the health-related outcomes of nonadherence ( 42 , 43 ). Language, acculturation, and nonadherence Only two studies explored the relationship between patients' preferred language and nonadherence, and both found that monolingual Spanish speakers were significantly more likely to be nonadherent ( 45 , 56 ), even after controlling for important cofactors, such as age and number of symptoms. In the two studies that evaluated the interaction between acculturation and nonadherence, one found that acculturation was not related to adherence ( 41 ) and one found that less acculturated patients were significantly less adherent ( 42 ). If language is used as a proxy for acculturation ( 63 , 64 , 65 , 66 ), then three ( 42 , 45 , 56 ) of four studies ( 41 , 42 , 45 , 56 ) found higher nonadherence in less acculturated Latinos. Because socioeconomic status is likely a particularly important potential cofactor in the relationship between nonadherence and language or acculturation, we examined whether each of these studies controlled for socioeconomic status. Of the studies that found that monolingual Spanish speakers were more likely to be nonadherent, one study controlled for socioeconomic status by controlling for education and health insurance status ( 45 ), and in the other study all patients had similar socioeconomic status and access to services ( 56 ). In the studies that examined acculturation, one controlled for socioeconomic status ( 41 ) and found that socioeconomic status, but not acculturation, was significantly associated with nonadherence. The other did not control for socioeconomic status, but a majority of participants were from similarly lower socioeconomic groups ( 42 ). Providers' language and ethnicity and nonadherence One study that assessed the effect of providers' language found that Latino patien