Parental exposure of cannabinoids THC and CBD reduces reproductive rates in Drosophila melanogaster

The FDA discourages women from using marijuana during pregnancy or breastfeeding on the basis that cannabinoids such as THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol) can negatively affect fetal brain development. However, despite increasing accessibility of cannabinoids, their impact on fertility, pregnancy, and reproduction rates has not been well studied. We hypothesized that CBD and THC, would reduce reproductive rates in Drosophila melanogaster. Our experiments were designed to show how cannabinoids might impact hatch rates in Drosophila by exposing them to previously reported concentrations of CBD and THC. We did a hatch assay with the control, THC, and CBD to compare rates of hatching between controls and flies treated with either 0.5 mg/mL THC or 0.5 mg/mL CBD. Compared to control groups, both cannabinoid groups showed a statistically significant decrease in reproductive rates. The control group had a hatch rate of 94.8%, while the CBD and THC groups had hatch rates of 86.2% and 89.6%, respectively. In the THC group, pupae were noted to turn red and die before emerging. While we predicted cannabinoids would reduce reproductive rates, we had expected THC would have the greater impact on reproduction. The results from our experiments indicated that CBD showed a greater reduction on hatching than THC. However, THC caused unusual and unexpected mortalities. This study provides evidence that cannabinoids such as THC and CBD reduce the rate of reproductive success, although the exact mechanism requires further study.