While some studies have explored the effects of marijuana on testosterone levels, the findings are inconsistent. Some studies suggest that marijuana use may slightly lower testosterone levels in some individuals, while others show no significant effect or even a temporary increase. However, even if marijuana did affect testosterone levels, the changes are unlikely to be significant enough to noticeably impact facial hair growth.
In summary, facial hair growth depends on genetics and hormones, and there's no scientific evidence to suggest that smoking weed has any effect on it.