Utilizing reliable and clinically significant change criteria to assess for the development of depression during smoking cessation treatment: the importance of tracking idiographic change.

Studies typically measure mood changes during smoking cessation treatment in two ways: (a) by tracking mean change in depression scores or (b) by tracking the incidence of major depression development using diagnostic assessments. However, tracking mean change does not capture variability in individual mood trajectories, and diagnosing participants at multiple time points is time and labor intensive. The current study proposes a method of assessing meaningful increases in depression without the use of diagnostic assessments by utilizing reliable and clinically significant change criteria. This method was applied to 212 participants in a smoking cessation trial to explore the relationship between smoking status and depressed mood, assessed at baseline, end-of-treatment, and 2-, 6-, and 12-month follow-ups. High rates of reliable (24-28%) and both reliable and clinically significant increases (23-24%) in depressed mood were observed across all participants, regardless of whether or not they achieved abstinence. However, when we calculated group mean change in depression during the trial, only decreases in depressed mood where observed across several intervals. Findings indicate that utilizing reliable and clinically significant change criteria to track symptoms of depression during smoking cessation treatment leads to different conclusions than simply tracking mean changes. We propose that a combination of reliable and clinically significant change criteria may serve as a useful proxy measure for the development of major depressive disorder during smoking cessation.