Published in the July-September 2021 edition of the journal Cognitive Development, this study assessed 804 adolescents at age 14 and 19.
They found that decision-making skills were not compromised when cannabis is used in moderation, and initial onset of use is after age 15. The following quote didn't make the headlines, but it basically says light cannabis use in adults improved decision-making skills:
"After controlling for confounders, light cannabis use as well as late-onset thereof was associated with increased decision-making skills both cross-sectionally at follow-up as well as longitudinally compared to non-using controls."
The link to the abstract is here.