Patterns of Risky Drinking Behaviours and Simultaneous Substance Use: A Cross-Sectional Survey of Australian Adults

Abstract Background. Alcohol and other drug use are major contributors to preventable health and social harms, with additional pharmacological and behavioural risks arising when substances are used simultaneously (i.e., in the same occasion). However, evidence on the frequency of simultaneous use and its relationship with risky drinking remains limited. This study examined patterns of illicit drug use, the frequency of simultaneous alcohol and illicit drug use, and its association with risky and heavy episodic drinking among a large sample of Australian adults. Method. Participants (N = 899; 56.2% women; Mdn age = 33; IQR = 26–44) were recruited through paid social media advertising and snowballing, and completed a cross-sectional online survey. The survey included demographic questions, measures of alcohol use (AUDIT-10), illicit drug use, and simultaneous use. Results. Risky/hazardous drinking (AUDIT ≥ 8) and frequent (weekly or more) heavy episodic drinking were reported by 40.1% and 18.3% of participants, respectively. In total, 52.3% of participants reported lifetime illicit drug use and 28.3% reported past four-week use. Cocaine had the highest rate of co-use with alcohol, with 49.7% of participants reporting that they often or always used the substances together, followed by ketamine (35.6%) and MDMA (33.2%). For each alcohol–drug combination examined, participants who frequently used the two substances together (often/always) had higher AUDIT scores than those who did so less frequently (never/rarely/sometimes; p < .05). Frequent heavy episodic drinking was also more common among frequent co-consumers for every combination except alcohol and heroin. Conclusions. The findings have important implications for policy and practice, including the need for drug literacy education and screening to identify individuals at greater risk of harm. Coordinated alcohol and drug policies should be developed to address the risks of co-use, particularly among individuals who combine alcohol and other drugs during episodes of heavy drinking.