Association between psychological status and health-related quality of life in 337 stable COPD patients according to working status (a), COPD severity (b), and comorbidities (c). Multivariate models adjusted by covariates in Table 3. The dots represent the regression coefficients and the vertical bars indicate the 95% confidence intervals. These estimates are interpreted as the change in SGRQ score (points) with respect to the reference group (subjects with neither anxiety nor depression (horizontal line)). Subjects with depression only were not included due to small sample size. † Chronic diseases from the Charlson index. One: only COPD; two or more: one or more in addition to COPD.