Clinicians need to obtain a detailed alcohol and drug use history in order to assess the inter-relationships between alcohol use disorder and polydrug use. Because polydrug use can be episodic and may or may not include dependence on one or more substances, the detailed history is key to the assessment and subsequent diagnostic formulation. For example, episodic patterns of substance use may relate to specific situations and therefore be potentially amenable to specific behavioural intervention; also, one (or more) of the substances used may be related in some ways, like some opioid dependent people may use benzodiazepines to augment opioid effects or an alcohol dependent person taking stimulants to increase alertness and possibly even to facilitate further drinking. 

Regarding screening for alcohol use disorder and polydrug use, there is a validated and recommended screening tool developed by WHO for the assessment of multiple drug use, the “Alcohol, Smoking and Substance Involvement Screening Test” (ASSIST; See Appendix). This screening tool has been designed to detect substance use (including multiple substances) and related problems in primary and general medical care settings, emergency departments and hospital outpatient settings, including obstetric units. The ASSIST provides a valid measure of substance-related risk both for the individual substances and for total substance use involvement. This screening tool can distinguish between people who are low risk substance users and those who have developed or are at risk of developing problems, including dependence on alcohol or other substances. The ASSIST is freely available online and also as an application for smart devices (“eASSIST”) which can be used by patients and automatically scored for the clinician (see Appendix).  

In some cases, the degree of complexity related to comorbidity and risks may indicate to the clinician at the time of screening that specialist assistance be obtained. Addiction medicine specialists may work collaboratively with other clinicians in managing complex patients as clinically indicated.