“Cannabis has been around for a long time, but it has not been well studied,” said Harriet de Wit, PhD, a Professor in the Department of Psychiatry and Behavioral Neuroscience at the University of Chicago.
They found that increasing doses of THC can increase bodily anxiety in women, and that compared to adults, adolescents are more negatively impacted by THC on cognitive tasks.
Conor Murray, PhD, became interested in studying THC from the historical use of cannabis and other plants as instruments for spiritual experiences.
What scientists do not know is whether the larger quantities of CB1R earlier in life mean that adolescents are more sensitive to cannabis.
Subjects across groups were matched for several important factors, such as sex, weight, and tolerance to cannabis, which was measured by the frequency and total instances of cannabis use.
During all sessions, Murray recorded three types of data: 1) EEG, a physical signature of cognition, 2) performance on several cognitive behavioral tasks; and 3) subjective answers to questionnaires.
To gather EEG recordings, 128 electrodes were placed on participants’ heads as they either rested with eyes closed or engaged in an attention-demanding task.
But as soon as they need to do a job, like making sense of the visual field when you open your eyes, they start chattering with each other — you can’t hear the synchronous activity anymore.” Alpha waves are much weaker in brains that are engaged in demanding tasks, which require individual neurons to “chatter” with one another.
“My interpretation is that as you become an adult, you’re able to carry on individual conversations between neurons much more readily,” said Murray, which is needed for proper task execution and breaks up the synchronous alpha wave.
THC had no detectable effect on brain waves at rest in either the adults or adolescents, but the differences in how THC affects the brain and cognition between the age groups became clear during task performance.
The tasks required subjects to stay attentive, react rapidly — or stop themselves from reacting too rapidly, recall the recent past, and judge how much time has passed.
Throughout the session, participants completed a series of questionnaires on their subjective experience.
This has implications for use of cannabis in conjunction with tasks like driving, which could be more dangerous for adolescents, or in a school setting, where adolescents may not be able to learn or demonstrate learning as effectively.
In addition, this study powerfully links the biochemical and cognitive levels of the human brain, as the higher concentrations of one receptor in adolescents — CB1R — is reflected in their cognitive performance.
Some receptors have the opposite pattern to CB1R: the levels of dopamine 1, the receptor responsible for the effects of cocaine and methamphetamine, increase in adulthood.
“A lot of knowledge may not hold true in females.” Historically, subjects in animal and human studies — across all of science — have been male.
Her paper is one of the first to examine the effects of THC specifically in women, and is part of a larger study on the interaction of THC and the menstrual cycle.
This is the longest phase of the cycle and starts on the first day of a period and lasts until an egg is released.
Pabon and her colleagues found that two autonomic heart measures – heart rate and high frequency heart rate variability — were related to THC dose.
While heart rate measures how fast your heartbeat is at any point in time, heart rate variability measures how fast your heart rate changes over a longer period.
So, while physical responses to higher doses of THC are reflected in subjects’ feelings, anxiety is not one of them.
“When they feel their heart rate increasing, they will interpret that as anxiety.” Subjects in the study did have higher heart rates at higher THC doses and noticed it themselves, but they did not self-associate it with anxiety.
However, others using cannabis in the real world might link their increased heart rates with anxiety, leading to a self-fulfilling cascade.
And if sex and hormones are not variables of concern for THC anxiety responses, she said that is an “important result from a scientific and safety point of view.” It is too soon to rule out the impact of hormones altogether.
The study, “Adolescents are more sensitive than adults to acute behavioral and cognitive effects of THC”, was published February 2, 2022 in Neuropsychopharmacology.