After adjustment, the difference across morbidity groups was highly significant (contrast P < 0.001), with odds ratios of 0.81 (95% CI = 0.77, 0.85, P < 0.001) for the multimorbidity group and 0.94 (95% CI = 0.90, 0.98, P = 0.006) for the single morbidity groups, relative to patients without a medical condition.
The interaction between multimorbidity and the presence of a mental health condition was marginally significant when added to the main effects model (contrast P = 0.046), with odds ratios of 0.95 (95% CI = 0.88, 1.04; P = 0.26) for the one‐condition group and 0.91 (95% CI = 0.84, 0.98; P = 0.02) for the multimorbidity group, relative to the no‐condition group, suggesting that the presence of a mental health condition decreases quit probability among people with multimorbidity by more than it does among other participants.