BackgroundConsultation-Liaison Psychiatry (CLP) is a subspecialty of psychiatry that provides care to inpatients under non-psychiatric care. Despite evidence of benefits of CLP for inpatients with psychiatric comorbidities, referral rates from hospital doctors remain low. This review aims to understand barriers to CLP inpatient referral as described in the literature.MethodsWe searched on Medline, PsychINFO, CINAHL and SCOPUS, using MESH and the following keywords: 1) Consultation-Liaison Psychiatry, Consultation Liaison Psychiatry, Consultation Psychiatry, Liaison Psychiatry, Hospital Psychiatry, Psychosomatic Medicine, the 2) Referral, Consultation, Consultancy and 3) Inpatient, Hospitalized patient, Hospitalized patient. We considered papers published between 1 Jan 1965 and 30 Sep 2015 and all articles written in English that contribute to understanding of barriers to CLP referral were included.ResultsThirty-five eligible articles were found and they were grouped thematically into three categories: (1) Systemic factors; (2) Referrer factors; (3) Patient factors. Systemic factors that improves referrals include a dedicated CLP service, active CLP consultant and collaborative screening of patients. Referrer factors that increases referrals include doctors of internal medicine specialty and comfortable with CLP. Patients more likely to be referred tend to be young, has psychiatric history, live in an urban setting or has functional psychosis.ConclusionThis is the first systematic review that examines factors that influence CLP inpatient referrals. Although there is research in this area, it is of limited quality. Education could be provided to hospital doctors to better recognise mental illness. Collaborative screening of vulnerable groups could prevent inpatients from missing out on psychiatric care. CLP clinicians should use the knowledge gained in this review to provide quality engagement with referrers.