Statistical analysis
Survey responses were tabulated and reported as counts and percentages. Current users were compared to non-current users of each substance for all analyses. To assess differences in socioeconomic characteristics, demographics, and illness severity markers, Fishers exact test was used. Univariate and multivariate logistic regressions were performed to evaluate the unadjusted and adjusted association between usage of CFTR modulators and current usage of each substance. Potential confounders included in the multivariate models were chosen a priori based on prior literature and a directed acyclic graph of the framework of potential relationships of use of CFTR modulators and substance use. Potential confounders were gender (female, male, other), age (13-25, 26-39, 40-80 years old), race and ethnicity (non-Hispanic White, Asian/Black/Hispanic/other race), FEV1 percent predicted (<60%, 60-79%, >80%), PHQ-4 (normal/mild, moderate/severe). Subjects with missing data were excluded from the regression analyses. A p-value of less than 0.05 was considered statistically significant. All statistical analyses were conducted using R version 4.2.1 (R Foundation for Statistical Computing, Vienna, Austria). The study procedures were reviewed and approved by the Institutional Review Board at the University of California, San Francisco (21-34926).