Long-Term Consequences of Adolescent Exposure to THC-Rich/CBD-Poor and CBD-Rich/THC-Poor Combinations: A Comparison with Pure THC Treatment in Female Rats

Cannabis is widely used by adolescents, and animal studies have shown long-term harm from its main psychoactive component, THC, but often ignore other cannabinoids like CBD. In female rats, giving THC and CBD together in a 3:1 ratio—based on illegal cannabis samples—reduced some behavioral changes and alterations in CB1 receptors and microglia in the prefrontal cortex caused by THC alone. However, a combination resembling 'light cannabis' (CBD:THC at 33:1, total THC 0.3%) caused lasting cognitive problems and anhedonia, along with increased GAD67 levels in the prefrontal cortex, indicating possible long-term effects on GABA signaling.

Study at a glance

Abstract

Cannabis is the most-used recreational drug worldwide, with a high prevalence of use among adolescents. In animal models, long-term adverse effects were reported following chronic adolescent exposure to the main psychotomimetic component of the plant, delta-9-tetrahydrocannabinol (THC). However, these studies investigated the effects of pure THC, without taking into account other cannabinoids present in the cannabis plant. Interestingly, cannabidiol (CBD) content seems to mitigate some of the side effects of THC, at least in adult animals. Thus, in female rats, we evaluated the long-term consequences of a co-administration of THC and CBD at a 3:1 ratio, chosen based on the analysis of recently confiscated illegal cannabis samples in Europe. CBD content is able to mitigate some of the long-term behavioral alterations induced by adolescent THC exposure as well as long-term changes in CB1 receptor and microglia activation in the prefrontal cortex (PFC). We also investigated, for the first time, possible long-term effects of chronic administration of a THC/CBD combination reminiscent of “light cannabis” (CBD:THC in a 33:1 ratio; total THC 0.3%). Repeated administration of this CBD:THC combination has long-term adverse effects on cognition and leads to anhedonia. Concomitantly, it boosts Glutamic Acid Decarboxylase-67 (GAD67) levels in the PFC, suggesting a possible lasting effect on GABAergic neurotransmission.