Examining the relationship between cannabis use and drinking levels on co-use days

Area of Science:

• Addiction research
• Public health
• Substance use epidemiology

Background:

• Co-use of alcohol and cannabis is prevalent among young adults.
• Existing research often links co-use to increased alcohol consumption but lacks focus on cannabis use during heavy drinking episodes.
• Young adults report drinking levels exceeding heavy episodic drinking (HED), reaching high-intensity drinking (HID) levels, which carry greater risks.

Purpose of the Study:

• To investigate the association between day-level alcohol and cannabis co-use and heavier drinking levels (HID, HED, moderate drinking).
• To explore how variations in cannabis use characteristics (frequency, form, quantity) influence drinking levels on co-use days.

Main Methods:

• A study involving 318 young adults from three US universities who reported simultaneous alcohol and cannabis use.
• Participants completed five repeated daily surveys over 54 days.
• Data collected included number of alcoholic drinks, cannabis use frequency/events, forms, and quantity consumed.

Main Results:

• Co-use days were associated with a higher likelihood of high-intensity drinking (HID) and heavy episodic drinking (HED) compared to moderate drinking.
• No significant difference in HID versus HED was found between co-use and alcohol-only days.
• On co-use days, increased cannabis consumption correlated with heavier drinking levels; specific cannabis forms (flower, concentrates) and quantities influenced HID likelihood.

Conclusions:

• Heavy drinking (HID, HED) is more probable on days when young adults co-use alcohol and cannabis compared to moderate drinking.
• Characteristics of cannabis use, such as quantity, appear to modulate alcohol consumption levels during co-use.
• Interventions targeting co-use should consider addressing both heavy drinking patterns and specific cannabis use behaviors.