Teenage brain tangled with marijuana and alcohol

Weed and Alcohol: Unraveling the Impact on Adolescent Brains

Rhea Morgan in Health & Wellness August 2025 • 4 min read.

"A deep dive into how combining cannabis and alcohol affects teenage ingestive behaviors, cognitive functions, and overall health"

The co-use of alcohol and marijuana is a prevalent and growing trend, particularly among adolescents and young adults. While both substances are often used recreationally, the combined effects on the developing brain remain largely unexplored. Understanding how these substances interact is crucial, especially given the unique vulnerabilities of the adolescent brain.

A new study investigates the combined effects of alcohol and Δ9-tetrahydrocannabinol (THC), the main psychoactive component of marijuana, on ingestive behaviors and cognitive functions in adolescent male rats. By examining how these substances interact, the research aims to shed light on the potential consequences of co-use during this critical developmental period.

This article breaks down the key findings of the study, translating complex research into accessible insights. From appetite and weight changes to impacts on memory and learning, we’ll explore the surprising ways alcohol and THC interact and what these findings could mean for adolescent health.

How Do Alcohol and THC Affect Appetite and Weight?

Teenage brain tangled with marijuana and alcohol

The study reveals that the route of THC administration—whether through injection or ingestion—significantly influences its effects. Subcutaneous THC injections increased short-term food intake but reduced overall weight gain. Interestingly, moderate alcohol consumption seemed to lessen the acute hyperphagic (overeating) effect of THC. Oral THC, on the other hand, robustly reduced alcohol intake without affecting short-term food consumption. At higher doses, some rats even stopped consuming THC-laced cookies.

One of the intriguing findings was the interaction between alcohol and THC on weight gain. While oral THC reduced weight gain, co-exposure to alcohol seemed to alleviate this effect, suggesting a complex interplay between the two substances on energy balance.

Here are the key findings:

Subcutaneous THC increased short-term food intake and reduced weight gain.
Moderate alcohol consumption reduced the hyperphagic effect of injected THC.
Oral THC reduced alcohol intake, especially at higher doses.
Alcohol alleviated the weight-reducing effect of oral THC.

These findings highlight that the combined use of alcohol and THC can lead to unique and sometimes opposing outcomes on ingestive behaviors and energy balance. This emphasizes the importance of considering both substances when assessing the potential health impacts on adolescents.

Why Does This Research Matter?

This research provides critical insights into how alcohol and THC interact in the developing brain, underscoring the potential for unique and sometimes counterintuitive outcomes on ingestive behaviors and energy balance. By establishing a novel model for studying voluntary alcohol and THC consumption, this study paves the way for deeper investigations into the mechanisms underlying adolescent substance use and its long-term consequences. Understanding these interactions is essential for informing public health strategies and interventions aimed at promoting adolescent health and well-being.

About this Article -

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Everything You Need To Know

How does the method of THC consumption (injection vs. oral) affect appetite and weight, and how does alcohol play a role?

Research indicates that when THC is administered through subcutaneous injections, it tends to increase short-term food intake but reduce overall weight gain. Conversely, moderate alcohol consumption appears to lessen the hyperphagic effect, or overeating, induced by THC. When THC is taken orally, it generally reduces alcohol intake. At higher doses, rats even stopped consuming THC-laced cookies. This highlights the complexity of how combined alcohol and THC use can lead to conflicting outcomes on ingestive behaviors and energy balance.

How does alcohol affect the weight-reducing effect of oral THC, and what does this suggest about energy balance?

The study found that oral THC reduced weight gain in adolescent male rats. However, co-exposure to alcohol seemed to alleviate this effect. This suggests a complex interplay between alcohol and THC on energy balance and body weight regulation. Further studies are needed to fully understand the mechanisms behind this interaction.

Why is it important to research the combined effects of alcohol and THC on adolescent brains?

This research is crucial because it provides valuable insights into how alcohol and THC interact in the developing brain. It highlights the potential for unique and sometimes counterintuitive outcomes on ingestive behaviors and energy balance. The study establishes a novel model for studying voluntary alcohol and THC consumption, which paves the way for deeper investigations into the mechanisms underlying adolescent substance use and its long-term consequences. Understanding these interactions is essential for informing public health strategies and interventions aimed at promoting adolescent health and well-being.

While the study focuses on rats, what are the potential implications of these findings for human adolescents who consume alcohol and THC?

The study specifically investigated adolescent male rats, so the direct implications for adolescent humans require further research. However, the findings suggest that combining alcohol and THC can have significant and complex effects on appetite, weight, and potentially other cognitive functions in adolescents. These findings underscore the importance of understanding the potential risks associated with co-use during this critical developmental period. Future research should focus on understanding the specific mechanisms underlying these effects and determining whether similar effects are observed in human adolescents.

What exactly is Δ9-tetrahydrocannabinol (THC), and why was it specifically studied in this research?

Δ9-tetrahydrocannabinol, commonly known as THC, is the primary psychoactive compound found in cannabis. The study used THC to examine its effects, both alone and in combination with alcohol, on adolescent male rats. By isolating THC, the researchers could specifically assess its impact on ingestive behaviors and cognitive functions, providing insights into the potential consequences of marijuana use during adolescence. This targeted approach helps to differentiate the effects of THC from those of other compounds found in cannabis.