Substance Use and Psychiatric Disorders in Patients Referred to Consultation-Liaison Psychiatry Within a Regional General Hospital

Little is known about important biopsychosocial differences between patients depending on the number of diagnosed comorbid psychiatric disorders, including the presence or absence of substance use disorder (SUD) comorbidity. This study investigated for differences in psychosocial disadvantage, psychiatric disorders, and health service utilization amongst 194 general hospital patients referred to consultation-liaison psychiatry (CLP) with either no psychiatric diagnosis, single psychiatric diagnosis, multiple (non-SUD) psychiatric diagnoses, or one or more psychiatric diagnoses plus SUD comorbidity. The results revealed that SUDs were the commonest diagnostic category (34%). The SUD comorbidity group had the highest rates of disadvantaged housing, were prescribed the most psychoactive medications, and 20% prematurely self-discharged against medical advice. Increased SUDs were associated with reduced length of stay, men, younger age, increased investigations, and reduced private health insurance subscription. Patients with SUD comorbidity versus multiple psychiatric diagnoses had reduced odds of adjustment disorder, somatic symptom disorder, and insomnia disorder. Post-traumatic stress disorder was the strongest predictor of multiple SUDs, followed by cluster B personality disorders. In conclusion, SUDs have become a leading clinical focus for CLP. The presence or absence of SUDs amongst patients with multiple disorders has important implications for engagement in treatment, patterns of comorbidity, and prescribing practices.