Fig. 3.

Frequency and severity of depression according to the GOLD classification of airway limitation (A) and the COPD assessment test (CAT) groups (B). Depression frequency did not differ significantly by airway limitation (A; P = 0.087 and P = 0.283 by chi-square test and linear-by-linear association, respectively). Depression frequency was significantly different between CAT groups (B; P < 0.001 and P < 0.001 by chi-square test and linear-by-linear association). FEV₁, forced expiratory volume in 1 second.