Introduction: Medication non-compliance is a serious barrier among chronically mentally ill patients. Horne defined it as the degree to which the patient's medication intake does not match with the prescriber’s suggestions. Many factors may be affecting medication non-compliance these factors divided to patient-related factors, disease-related factors, and healthcare system-related factors. Many studies fined that patients’ characteristics, may impact on attitudes, beliefs, medicines, and disease as well as health locus of control are directly related to treatment adherence.

Objective: The present study attempts through a systematic literature review to determine the relationship between beliefs about medicines and health locus of control to the degree of medication compliance of patients with mental disorders.

Methods: A systematic literature review was conducted at PubMed / Medline and Google Scholar databases, using the key terms: Mentally Ill, Mental Disorders, Medication Non-Compliance, Medicines Opinions, and Health Locus of Control in both languages Greek and English, without a time limit. Articles that met the inclusion criteria and addressed the degree of medication compliance in relation to beliefs about medicines and health locus of control in patients with mental disorders were studied.

Results: Many studies in the literature appeared to agree that the beliefs about mentally ill and the medicines they take, as well as the health locus of control can positively interact towards medication compliance.