Moons P, Luyckx K, Kovacs AH, et al. - Researchers examined the prevalence of cigarette smoking, cannabis consumption, and co-use among persons with congenital heart disease (CHD) as well as determined inter-country differences in these prevalences. Further, they assessed the relative effects of cigarette smoking, cannabis use, or co-use on physical functioning, mental health, and quality of life (QOL) and quantified their differential effect on these outcomes. In APPROACH-IS, a cross-sectional study, 4,028 adults with CHD were included from 15 countries. Overall, only cigarette smoking was reported in 14% of men and 11% of women; 8% of men and only cannabis use was reported in 4% of women; and use of both substances was reported in 4% of men and 1% of women. Outcomes revealed that cigarette and cannabis use in adults with CHD vary significantly between countries. Patient-reported outcomes were most detrimentally affected by co-use.