Moons P, Luyckx K, Kovacs AH, et al. - Among adults with congenital heart disease (CHD), researchers focused on the prevalence of cigarette smoking, cannabis intake, and co-use in a cross-sectional study, named APPROACH-IS. They also determined intercountry differences and examined the relative influences on physical functioning, mental health, and quality of life. Additionally, they quantified the differential impact of cigarette smoking, cannabis use, or co-use on those results. A total of 4,028 adults with CHD from 15 countries were included. Having smoked cigarettes only was reported by 14% of men and 11% of women, and having consumed cannabis only was stated by 8% of men and 4% of women, and use of both substances was noted in 4% of men and 1% of women. Findings revealed significant intercountry variability in cigarette and cannabis use in adults with CHD. The prevalence of cigarette smoking was found to be highest in the Switzerland and that for cannabis use was highest in Canada. Co-use influenced patient-reported outcomes in the most detrimental way.