Psychiatric Medication Adherence in Patients Experiencing Homelessness

Patients with mental illnesses can decompensate and relapse due to poor adherence to psychotropic medications.¹ Reasons for nonadherence include a lack of understanding of the illness, a lack of social support, and the adverse effects (AEs) of medication.^1,2 Previous study data have demonstrated that patients with mental illnesses who are experiencing homelessness may have additional barriers to medication adherence related to not having a secure storage space, which can result in stolen or lost medications.^1-5 However, there are likely many other potential barriers for this population that have not been fully explored or addressed.

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The medication adherence rate for the homeless population was reported previously as 30% to 41%, which is lower than the overall medication adherence rate for psychiatric patients of 44% to 58%.² A Medicare cost-analysis conducted in California’s San Diego County from 1998 to 2000 found that 26% of patients experiencing homelessness were adherent to their schizophrenia medications compared with 36% to 50% of patients with more stable living situations.³ More recent data after the COVID-19 pandemic are not available.

In a recent initiative, we attempted to analyze medication adherence rates at Sharp Mesa Vista (SMV) Hospital, the largest psychiatric hospital in San Diego, to identify possible reasons leading to nonadherence in patients admitted to the hospital, both those experiencing homelessness and those who were not admitted to the hospital.

Reviewing Medication Adherence

According to the WeAllCount Census for 2022 to 2023,⁶ homelessness in San Diego increased by 22% (from 8427 to 10,264 individuals). A retrospective chart review of those admitted to SMV Hospital in 1 year (July 1, 2022-June 30, 2023) was conducted to identify whether there is a difference in the medication adherence rate in patients experiencing homelessness compared with patients who are not.

Patients 18 years or older with inpatient admission to SMV were included in the review. Patients were excluded if they had a primary mental health diagnosis of a substance use disorder or no documented Behavioral Health Initial Assessment Form in the electronic medical record. Patients with a primary diagnosis of a substance use disorder were excluded because medications used to treat the disorder (eg, naltrexone, acamprosate, disulfiram) vastly differ from the psychotropics (eg, antidepressants, antipsychotics, benzodiazepines) used in common psychiatric disorders, such as depression, anxiety, and schizophrenia. During the review, nonadherence was defined as not taking at least 1 home psychiatric medication as prescribed at admission.

Reasons for medication nonadherence between the 2 groups were also compared, as well as Medication Adherence Rating Scale (MARS) scores. MARS is a self-reported 10-item questionnaire to measure psychiatric medication adherence (Table 1).⁷ Three factors are assessed on the questionnaire: medication adherence behavior (items 1-4), attitudes toward taking medication (items 5-8), and negative adverse effects and attitudes to psychotropics (items 9 and 10).⁷ Total scores range from 0 (low likelihood of medication adherence) to 10 (high likelihood of adherence).⁷ To obtain a score of 10 on the questionnaire, patients must answer no for questions 1 to 6, 9, and 10, and yes for questions 7 and 8, with 1 point allocated for each.⁷

The initial data pull conducted by the clinical analyst for the time frame mentioned previously retrieved 325 patients. After a thorough chart review of each patient’s profile, 278 patients met the inclusion criteria, and 47 were excluded for not having any documented psychiatric home medications. More patients were identified as nonhomeless (n = 224) than as experiencing homelessness (n = 54).

Generally, the majority of patients in both groups were in the age group of 18 to 34 years, were taking 1 to 2 psychiatric medications at baseline, and had a primary behavioral health diagnosis of depression, bipolar disorder, or schizophrenia spectrum disorder (Table 2). Male patients outnumbered female patients in the homeless group (72% vs 28%), whereas the opposite was observed in the nonhomeless group (38% vs 62%). Moreover, the mean number of baseline behavioral health diagnoses was higher in the homeless group (4.46) than in the nonhomeless group (3.75).

Per the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, a patient with sheltered homelessness is defined as an individual whose primary nighttime residence is a homeless shelter, warming shelter, domestic violence shelter, motel, or temporary or transitional living situation.⁸ A patient with unsheltered homelessness is defined as an individual residing in a place not meant for human habitation (eg, public space, building not intended for residential use, car, cardboard box).⁸ By these definitions, more patients experiencing homelessness were sheltered than unsheltered (Table 3). The living situation of 22% of the patients experiencing homelessness was unknown.

Nonhomeless patients had a higher adherence rate to their home psychiatric medications at the time of admission (62%) than patients experiencing homelessness (37%) (Table 4). Due to incomplete documentation, the MARS score could not be calculated for all the patients. Interestingly, of the available MARS scores, the average scores for both the nonhomeless and homeless groups were high, at 8.59 (n = 152) vs 8.54 (n = 26), respectively, suggesting a high likelihood of self-reported adherence. The reasons for nonadherence were similar between the nonhomeless and homeless groups (Table 5). However, the reasons that were more prevalent in the homeless population were lost and stolen medications and transportation issues (ie, the patients lacked transportation to their pharmacies to pick up prescriptions). Other top reasons for nonadherence were lack of perceived effect, relapse on alcohol or substances, forgetfulness, psychosocial stressors, and AEs from medications.

The Role of Pharmacists

Pharmacists can help to increase adherence rates by providing medication therapy management that identifies medication-related problems, creates a patient-centered medication action plan, and offers the patient referrals to other health care providers.¹ Additionally, pharmacists can conduct discharge counseling for patients at high risk for nonadherence to further improve outcomes.² The counseling session would include explaining the indication, dosing, AEs, storage information, and remaining refills of psychotropic agents, and addressing patient concerns regarding therapy.

Administration of long-acting injectable (LAI) antipsychotics may also improve adherence rates within the homeless population.² However, tolerability to oral formulations of an antipsychotic should be established before LAI administration. Another limiting factor of LAIs to keep in mind is that patients would be required to schedule appointments at a clinic to receive the injections, so transportation and the ability to come to the clinic should be addressed with patients prior to starting the medication. Pharmacists’ expertise and understanding of the role, pharmacological profile, and AEs of drugs make them an excellent resource for providing patient-centered care and addressing medication adherence with patients.

Medication adherence is important for the successful treatment of psychiatric or behavioral health diagnoses. Through additional insights and a better understanding of the barriers to medication nonadherence, pharmacists can highlight and help tackle the issues and make significant interventions to improve adherence.

REFERENCES

1. Coe AB, Moczygemba LR, Gatewood SB, Osborn RD, Matzke GR, Goode JVR. Medication adherence challenges among patients experiencing homelessness in a behavioral health clinic. Res Social Adm Pharm. 2015;11(3):e110-e120. doi:10.1016/j.sapharm.2012.11.004

2. Hird R, Radhakrishnan R, Tsai J. A systematic review of approaches to improve medication adherence in homeless adults with psychiatric disorders. Front Psychiatry. 2024;14:1339801. doi:10.3389/fpsyt.2023.1339801

3. Gilmer TP, Dolder CR, Lacro JP, et al. Adherence to treatment with antipsychotic medication and health care costs among Medicaid beneficiaries with schizophrenia. Am J Psychiatry. 2004;161(4):692-699. doi:10.1176/appi.ajp.161.4.692

4. Barry R, Anderson J, Tran L, et al. Prevalence of mental health disorders among individuals experiencing homelessness: a systematic review and meta-analysis. JAMA Psychiatry. 2024;81(7):691-699. doi:10.1001/jamapsychiatry.2024.0426

5. Unni EJ, Ashment R, Miller E, Draper AM. Medication nonadherence in the homeless population in an Intermountain West city. Innov Pharm. 2014;5(2). doi:10.24926/iip.v5i2.342

6. San Diego County’s Official Homeless Count Rises 22% to 10,264. June 8, 2023. Accessed June 2, 2025. https://timesofsandiego.com/politics/2023/06/08/san-diego-countys-official-homeless-count-rises-22-to-10264/

7. Thompson K, Kulkarni J, Sergejew AA. Reliability and validity of a new Medication Adherence Rating Scale (MARS) for the psychoses. Schizophr Res. 2000;42(3):241-247. doi:10.1016/s0920-9964(99)00130-9

8. 2021 DSM-5 diagnoses and new ICD-10-CM codes. American Psychiatric Association. Accessed June 2, 2025. https://www.psychiatry.org/psychiatrists/practice/dsm/updates-to-dsm/coding-updates/2021-coding-updates