Objective To examine unintentional alcohol and drug poisoning in association with substance use disorders (SUDs) and mood and anxiety disorders.

Method International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) external-cause-of-injury codes on discharge records of patients ages 12+ years from the 2010 Nationwide Inpatient Sample were examined to identify cases with unintentional alcohol poisoning (E860) and/or drug poisoning (E850–E858). ICD-9-CM diagnosis codes were examined to identify comorbid alcohol dependence, drug dependence, tobacco use disorder, and mood/anxiety disorders. Poisson regression was used to derive risk ratios to assess the associations between these comorbid conditions and alcohol/drug poisoning.

Results Estimated numbers of hospitalisations related to unintentional alcohol and drug poisoning were, respectively, 5623 and 60 423 in men, and 3147 and 68 568 in women. For both sexes, the proportion with SUDs or mood/anxiety disorders was significantly higher among inpatients with alcohol and drug poisoning than among all inpatients. Estimated risk ratios indicated strong relationships of SUDs and mood/ anxiety disorders with unintentional poisoning from alcohol and drugs. The strongest association was between alcohol dependence and alcohol poisoning for both sexes. Significant associations also existed between drug dependence and drug poisoning, and mood/anxiety disorders and poisoning from alcohol and drugs.

Conclusions SUDs and mood/anxiety disorders are key risk factors for unintentional poisoning by alcohol and drugs among inpatients in the USA. Effective treatments of these disorders should be targeted as poisoning prevention efforts. Future studies are needed to clarify a potential bias in the data due to differential inpatient mental condition screening practices.