Table 3.

Parameter estimates (in % of variance explained) for A (additive genetic variance), C (shared environmental variance), and E (unshared environmental variance) for initiation of cannabis use and problematic cannabis use as obtained from meta-analysis. Estimates are presented separately for males and females.

	Initiation of cannabis use			Problematic cannabis use
	A	C	E	A	C	E
Males	47.6 (38.8–56.4)	25.1 (11.5–38.7)	27.2 (18.2–36.2)	51.4 (37.9–64.9)	19.8 (11.3–28.3)	28.8 (22.2–35.3)
Females	39.6 (30.0–49.2)	39.0 (28.6–49.4)	21.2 (15.5–26.9)	58.5 (44.3–72.7)	15.2 (0.6–29.8)	26.3 (23.1–29.5)