We reviewed the literature to examine rates of, risk factors for, and influences of language and acculturation on antipsychotic, antidepressant, and mood stabilizer nonadherence among Latinos living in the United States. We found the mean rate of psychotropic nonadherence among Latinos was 44% in studies including only Latinos, and was approximately 40% in studies including multiple ethnic groups. This was higher than the mean rate of roughly 30% among Euro-Americans and was comparable to the rate of roughly 40% among African Americans. The effect size of the difference between rates for Latinos and Euro-Americans was 0.64, suggesting a medium to large difference. We purposely compared rates among ethnic groups using only studies that had rates available for all groups, so the higher nonadherence rates found in Latinos and African Americans compared to Euro-Americans are not due to differences in study design or adherence measure. A majority of individual studies found Latinos had significantly higher rates of nonadherence than Euro-Americans. Remarkably, none found that Latinos had lower nonadherence, even in bilingual, culturally tailored settings (56
), suggesting that Latinos experience additional barriers to adherence beyond language and cultural barriers.
Consistent with prior studies, nonadherence predicted worsened illness course in studies that investigated outcomes. Risk factors for nonadherence among Latinos identified in individual studies that are similar to those in the wider adherence literature included substance abuse, barriers to access to quality care, lacking health insurance, and limited family support. Two studies identified monolingual Spanish status as a nonadherence risk factor. If one considers poor English proficiency as a proxy for acculturation (63
), then three of four studies found less acculturation predictive of nonadherence. Protective factors for Latinos included greater family instrumental and financial support, higher socioeconomic status, older age, being married, being more proactive in one’s care, having public or private insurance, and having made 8 or more visits to a therapist.
Prior reviews have noted great variability in psychotropic nonadherence rates (10–77%), with mean rates of 35–60% (17
). The mean rates for Latinos and African Americans were within that mean range, but the Euro-American rate was slightly lower (30%). When examining only studies that used pharmacy data, MEMS caps, or urine testing, the nonadherence rates in all groups were higher (44% for Latinos and 49% for African Americans) and the Euro-American mean nonadherence rate was within the prior literature mean range (37%). Although studies relying on patient or provider report tend to underestimate nonadherence rates, all studies including only Latinos used patient, family, or provider report to measure adherence, yet surprisingly found higher mean nonadherence rates (44%) than studies using more objective measures (40%). This could be due to some using a combination of patient, family and chart review to assess adherence (43
). The higher rates could also be due to differences in study design or patient population, or there could be cultural factors that lead to patient and provider report being more reliable in Latino populations than non-Latino populations.
Family likely has a particularly important role in the caring for and health outcomes of Latino patients with mental illness compared to other ethnic groups (24
). Two studies investigated which specific types of family assistance were most predictive of adherence and found greater financial support from family (41
) and more family instrumental support (“task-oriented” assistance) (44
) predictive of better adherence.
Our review has several limitations. Although we conducted a comprehensive search, it is possible we missed a relevant study. This constitutes a comprehensive review of summary data, not a metanalysis. Included studies were heterogeneous with respect to study objectives and design, diagnoses studied, sample size, and proportion of Latino participants. Many of the larger studies were limited by small percentages of Latino patients. Additionally there was extensive variability in adherence measure, time over which adherence was measured (one week to one year), and even the definition of adherence, with some studies using dichotomous measures and others including partially adherent in addition to nonadherent and adherent. This heterogeneity, particularly the variability in time over which adherence was measured, likely led to the wide range in nonadherence rates seen between studies, even among studies using more objective adherence measures, as adherence is known to decrease over time (59
). Although this variability could affect the reliability of absolute nonadherence rates, it likely did not affect our ability to compare relative rates between ethnic groups since we included only studies that had rates available for all three groups. Therefore, we know that any ethnic group rate differences were not due to differences in adherence measure or study design. Also, we separately examined studies using only more typically objective adherence measures, and found somewhat higher nonadherence rates among all ethnic groups, but a similar pattern of relative rates between groups to that in the analysis including all reports. Another limitation of the literature was that none of the reports examined every risk or protective factor identified – in fact, many risk and protective factors were investigated only by one or a few studies – making conclusions about the relative importance of each factor impossible to determine. Only one study conducted cross-cultural comparisons of risk or protective factors. Similarly, we could not compare nonadherence rates or factors most relevant by diagnosis and ethnicity because most studies included participants with only one diagnosis. Additionally, a number of factors that likely significantly influence adherence among Latinos were not investigated, such as cultural attitudes and beliefs about mental illness and treatments, health literacy, stigma (68
), insight, efficacy and tolerability of medications, side effects, use of alternative treatments, and dietary and genetic effects on medication metabolism. Only a few studies examined factors unique to Latinos such as language and acculturation. Similarly, potentially modifiable mechanisms influencing adherence, such as socioeconomic status, health insurance, or barriers to quality care were merely examined in single reports. We were only able to draw comparisons in rates between Latinos, Euro-Americans, and African Americans due to the literature generally lacking adherence investigations in other ethnic groups. The US Latino population is quite heterogeneous both culturally and in important indicators of population health (24
). Many of these studies were conducted with Mexican-Americans and VA populations, so the results are likely not applicable to all Latino communities living in the United States.
It is important to note that the summary mean nonadherence rates were generally unadjusted for potentially important cofactors, such as socioeconomic status. Therefore these cofactors must be considered possible contributors to the lower nonadherence rates seen among Latinos and African Americans compared to Euro-Americans. Similarly, in considering possible explanations for the relationships between risk and protective factors and nonadherence, cofactors such as access to health care or socioeconomic status must be considered. For example, the relationship between less acculturation and nonadherence noted by three of four studies could be mediated by a variety of factors, including socioeconomic status. This remains an open question; two of the four studies examining acculturation did directly control for socioeconomic status, with one still finding an association between nonadherence and less acculturation (45
) and the other finding no association (41
). Other ways in which less acculturation could lead to nonadherence include impaired patient-physician communication due to language barriers (45
) or difficulty navigating the US healthcare system.
Despite these limitations, our results clearly suggest that Latinos are at higher risk for psychotropic medication nonadherence compared to Euro-Americans. Remarkably, this risk was observed across various study designs, diagnostic categories, medication types, clinical settings, and Latino subgroups. The higher rates of nonadherence seen in Latinos were comparable to the rates in African Americans, another disadvantaged ethnic minority. Although the existing literature limited our ability to answer the question of which risk factors are most relevant for Latinos, we have summarized all the influences on adherence in Latinos investigated to date, and identified factors particularly relevant for Latinos.
As previously recommended (17
), a standard definition and measure of adherence would greatly improve the translation of the broader adherence literature. Since people are less than optimally adherent to medications in different ways and for different reasons, quantifying adherence into more subcategories than simply adherent or nonadherent would be helpful in better understanding adherence and developing interventions to improve it. This has been done in more recent studies (6
), one of which, interestingly, found that excess fillers incurred the highest health care costs of all nonadherent patients (6
In terms of recommendations more specific for studying adherence among Latinos, we first encourage future adherence studies to include more adequate numbers of Latinos. This is consistent with the National Institute of Mental Health’s initiative to increase representation of ethnic minority participants in research studies (70
). Given the great heterogeneity of US Latino populations (71
), we recommend including Latinos from all the diverse cultural and socioeconomic backgrounds that make up the larger US Latino population, and specifying degree of acculturation, country of origin or cultural background, socioeconomic situation, and preferred language, as was done in many of the included studies. This heterogeneity also gives added weight to prior recommendations for local, community-based, participatory research (38
) to develop optimally relevant and lasting interventions to improve adherence. Additionally, we recommend cross-cultural comparisons investigating the relative importance of risk and protective factors for different ethnic groups, including Asians and American Indians – who we noted were rarely included in meaningful numbers in adherence investigations.
While adherence measures that rely on pharmacy records do not require translation, pharmacy records may be liable to underestimate adherence for patients in lower socioeconomic groups, who, for example, may rely on free samples from physicians (which would not be displayed in pharmacy records) to bridge gaps in insurance coverage or reduce prescription costs. Pharmacy records will also exclude herbal and over the counter medications which could affect adherence. Therefore, future studies may want to consider supplementing pharmacy or MEMS caps data with other sources of adherence data, such as patient and family report combined with chart review (44
), or detailed structured patient interviews (55
) to provide a comprehensive examination of nonadherence and its causes.
Ultimately, research needs to identify mechanisms whereby suboptimal adherence occurs among Latinos and ethnic minorities in general. Hypothesis-driven research characterizing the role of moderators and mediators of adherence is needed. Mechanisms thus identified would be the basis for more effective interventions. Our review gives additional support to the National Institute of Mental Health sponsored expert consensus meeting of Latino Mental Health Services researchers recommendation (38
) to investigate the effects on adherence of language, acculturation, family support, health insurance, poverty, and access to quality care including therapy. Given the findings that socioeconomic and health insurance status and barriers to quality care were related to adherence, these should be included as potential cofactors in future analyses of adherence. Particular attention should be paid to including these when comparing ethnic groups, because ethnic differences in adherence have been found to disappear when, for example, income was accounted for (73
). As previously noted (56
), preferred language may be a better predictor of health patterns than ethnicity. It is essential to include adequate numbers of Spanish-speaking as well as bilingual and English-speaking patients and clinicians in future research to better understand these relationships. In addition to further exploring the influence of factors noted in this review, we hope future studies will investigate other likely adherence influences. One such recently identified factor is stigma, which ranked second only to side effects in antidepressant use concerns identified by Latino focus groups (68
). Another is the role of culture in shaping the experience and interpretation of mental illness.
The trend noted in one study (40
) that Latinos with depression were more likely to be nonadherent than Euro-Americans with depression (but no difference was found for schizophrenia) deserves focused attention in future investigations. We recommend researchers examine nonadherence rates by both ethnicity and diagnosis. Also, cross-cultural explorations of which factors are most important for which diagnostic groups and whether mechanisms of nonadherence differ between diagnostic and ethnic groups would be a significant new contribution to the literature.
Due to the limitations of the literature described above, we cannot offer specific clinical recommendations at this time. However, the data do provide some general clinical guidelines. Currently there are no evidence-based interventions specifically to improve psychotropic medication adherence among Latinos. However, findings from broader quality improvement interventions (74
), adherence interventions in predominantly non-Latino populations (75
), adherence interventions for non-psychiatric diseases tested in Latinos (77
), broader mental health interventions for Latinos (80
), from clinical experience (82
) and policy papers (39
) are potentially applicable.
Since the majority of patients are likely to have adherence problems at some point (59
), reassessing adherence regularly and repeatedly is important. Incorporating pharmacy records (3
) in addition to patient and family report will increase the likelihood of catching adherence difficulties. The finding that Latino patients were less likely than Euro-Americans to discuss their medications with their physician (52
) suggests physicians should be particularly mindful to encourage medication discussions with their Latino patients. That physicians are proactive in these discussions is particularly important given that a common practice in many Latino cultures is to show deference towards physicians (83
). Depending on language preference and educational attainment, information about medication should be in Spanish and use simple terms enhanced with visual aids, where appropriate. Similarly, the prominence of stigma and culturally-influenced negative antidepressant associations in recent focus groups with Latinos prescribed antidepressants (68
), indicates that inquiring about and addressing these could be useful for improving adherence among Latinos.
Given the high prevalence of nonadherence in all populations, and that the reasons for nonadherence are likely different across patients, we strongly recommend assessing adherence and barriers to and mechanisms of adherence individually for every patient. While some factors identified in our review, such as young age, cannot be modified, other contributors to nonadherence could be addressed in clinical settings. The findings by two studies in this review -- that greater family financial and instrumental support were predictive of better adherence --suggest that involving family members in these specific ways whenever possible might be particularly beneficial to Latino patients. In addition, the increased antidepressant adherence among Latinos having 8 or more visits to a non-medical therapist (45
) is consistent with findings from predominantly Euro-American samples (57
), and a position paper (39
) calling for culturally appropriate practice-initiated quality improvement interventions, including psychoeducational and psychotherapeutic components. The finding that Latinos were more likely than Euro-Americans to want counseling and less likely to want antidepressants (85
) suggests therapy may be an especially important adherence enhancer for Latinos.
Latinos are least likely of all US ethnic groups to have public or private health insurance, with uninsured rates of 35.7% (compared to 12.6% for Euro-Americans) (86
). This disparity lends added significance to the finding that having public or private health insurance predicted better adherence among Latinos (45
). As lower socioeconomic status was associated with lower adherence (41
), and Latinos are disproportionately represented in lower socioeconomic strata (24
) clinicians should pay particular attention to ensuring their patients can afford the psychotropic medications they prescribe. Given barriers to quality care were associated with worse adherence, clinicians can likely improve adherence simply by ensuring they are providing quality care. These findings also suggest that societal level interventions increasing access to health insurance, medications, and quality care would improve adherence.
Culturally and linguistically tailored care is likely important for establishing good clinician-patient relationships, which have been associated with improved adherence (7
). Clinicians should attend to cultural contexts shaping how their patients interpret and experience mental illness, as these likely affect adherence. As previously noted in several papers (82
), and suggested by the findings of two studies in this review (41
), even clinics with primarily bilingual, bicultural staff can have cultural divides with their patients due to socioeconomic and health models and beliefs differences. Recognizing those divides and working collaboratively with patients can help overcome these barriers and improve adherence (82