Poor Adherence to Oral Psychiatric Medication in Adults with Schizophrenia May Be Influenced by Pharmacophobia, High Internal Health Locus of Control and Treatment Duration

Objective: This study in Spain, Argentina, and Venezuela included 212 schizophrenia outpatients prescribed 387 psychiatric medications and 1,160 other psychiatric outpatients prescribed 2,067 medications. Methods: Logistic regression models included adherence for each psychiatric medication, measured by the Sidorkiewicz Adherence Tool, as the dependent variable. The models provided adjusted odds ratios (ORs) of dichotomous independent variables: 1) clinical variables, 2) subscales from the Patient Health Beliefs Questionnaire on Psychiatric Treatment (presence/absence of pharmacophobia and pharmacophilia and high/low psychological reactance, internal health locus of control [HLOC] and doctor's HLOC) and 3) presence/absence of skepticism toward each medication measured by the Beliefs about Medicines Questionnaire (BMQ). Results: ORs significant in both groups were: 1) pharmacophobia (OR=0.389 in schizophrenia, OR=0.591 in other patients and not significantly different) and 2) pharmacophilia (respectively OR=2.18, OR=1.59 and significantly higher in schizophrenia: p=0.012). Prescribing the medication for >1 year increased adherence in schizophrenia (OR=1.92) while decreasing it in others (OR=0.687). Four ORs were significant in the schizophrenia group but not in the controls: treatment for >1 year (OR=0.161), high internal LOC (OR=0.389), extreme polypharmacy (OR=1.92) and the country of Spain (OR=0.575). Regarding antipsychotics, the study included 204 schizophrenia patients prescribed 240 antipsychotic medications and 301 other patients prescribed 315 antipsychotic drugs. Three ORs were significant for antipsychotic adherence in the schizophrenia group: pharmacophobia (OR=0.324), treatment for >1 year (OR=0.362), and skepticism about specific antipsychotics (OR=0.535). Conclusions: Future adherence studies for antipsychotic/all medications should further explore the specificity/commonality of these dimensions in schizophrenia versus other psychiatric patients. (Neuropsychopharmacol Hung 2021; 23(4): 388-404).