BACKGROUND: The prevalence and effects of cigarette smoking and cannabis use in persons with congenital heart disease (CHD) are poorly understood. We (1) described the prevalence of cigarette smoking, cannabis consumption, and co-use in adults with CHD; (2) investigated intercountry differences; (3) tested the relative effects on physical functioning, mental health, and quality of life (QOL); and (4) quantified the differential effect of cigarette smoking, cannabis use, or co-use on those outcomes.

METHODS: APPROACH-IS was a cross-sectional study, including 4028 adults with CHD from 15 countries. Patients completed questionnaires to measure physical functioning, mental health, and QOL. Smoking status and cannabis use were assessed by means of the Health Behaviour Scale-Congenital Heart Disease. Linear models with doubly robust estimations were computed after groups were balanced with the use of propensity weighting.

RESULTS: Overall, 14% of men and 11% of women smoked cigarettes only; 8% of men and 4% of women consumed cannabis only; and 4% of men and 1% of women used both substances. Large intercountry variations were observed, with Switzerland having the highest prevalence for smoking cigarettes (24% of men, 19% of women) and Canada the highest for cannabis use (19% of men, 4% of women). Cigarette smoking had a small negative effect on patient-reported outcomes, and the effect of cannabis was negligible. The effect of co-use was more prominent, with a moderate negative effect on mental health.

CONCLUSIONS: We found significant intercountry variability in cigarette and cannabis use in adults with CHD. Co-use has the most detrimental effects on patient-reported outcomes.