In a new study, young rats exposed to marijuana had a more a pleasurable first experience with cocaine compared to adult rats.

Evidence continues to mount regarding the adverse effects teenage marijuana consumption manifests later in life. Recent studies have linked smoking cannabis as an adolescent with developing insomnia issues and depression as an adult. New research now indicates early cannabis use rewires developing brains to become more sensitive to their first experience with cocaine.

The study, published this week in the Proceedings of the National Academy of Sciences, exposed adolescent and adult rats to a synthetic molecule resembling THC. Scientists found the younger rats underwent key molecular changes in their prefrontal cortex, though the adult rats did not experience these changes. Scientists then exposed these rats to cocaine. Once the young rat brains were rearranged, it made their first experience with cocaine more intense.

As previous studies have demonstrated, positive first experiences with a drug could lead to more addictive behavior down the road. This alteration becomes more problematic to individuals already genetically predisposed to developing addiction.

RELATED: Study: Teenagers Are Waiting To Experiment With Drugs Later In Life

“We know from human epidemiological studies that individuals who abuse cocaine have a history of early cannabis use, and that a person’s initial response to a drug can have a large impact on whether they continue to use it. But many questions remain on how early cannabis exposure affects the brain,” study senior co-author Denise Kandel said in a statement.

Using synthetic THC in the study was a limitation, researchers said, because synthetic THC binds more strongly to the brain’s endocannabinoids system than natural THC would. It’s also important to note researchers delivered increasing doses of synthetic THC over time in order to resemble “heavy” marijuana use as an adolescent. The conclusions of the study likely don’t apply to those who smoked cannabis a few times, especially if consuming a low-THC marijuana strain.

“The endocannabinoid system has a modulatory role in brain reward and cognitive processes,” researchers wrote. “It has been hypothesized that repeated interference with endocannabinoid signaling (e.g., through abuse of cannabis or synthetic cannabinoids) can remodel the adolescent brain and make it respond differently to more addictive substances, such as cocaine.”

RELATED: Teenage Marijuana Use Could Cause Adult Insomnia

The specific terms scientists used to describe this process was “cross-sensitization.” Further research is necessary to understand the relationship on a deeper level, and they stressed that a more pleasurable first cocaine experience doesn’t automatically qualify someone to become addicted to the substance.

“These and other experiments are key to understanding the molecular changes to the brain that occur during drug use,” study co-author Eric Kandel said in a statement. “This knowledge will be crucial for developing effective treatments that curb addiction by targeting the disease’s underlying mechanisms.”