We examined intra-individual variability in positive and negative mood states in N = 401 smokers (1) before and (2) after participants quit smoking. Pre-quitting, smokers were randomly assigned to 1) a nicotine replacement therapy (NRT) condition and 2) a placebo condition. Participants self-reported both positive and negative mood states at multiple time points during the day both pre and post quitting. In the present study, we hypothesized that NRT would not only lead to improvements in overall levels of positive and negative mood after quitting, but would also buffer the emotional disturbance faced during the quitting stage, resulting in lower intra-individual mood variability post-quitting in the NRT as compared to the Placebo group. Latent state-trait analyses revealed significant intra-individual variability in positive and negative mood states in both groups. Further, we observed a tendency for mood state variability to be reduced post-quitting in both groups. Post-quitting, variable situational (as opposed to temporally stable) influences accounted for only about 25% of the true score variance in positive mood states (as compared to about 40% pre-quitting). Variability in negative mood states also declined from the pre- to the post-quitting phase in both groups (from about 50% situational variance pre-quitting to about 30% post-quitting). Although NRT appeared to be generally beneficial for improving mean mood levels, results with regard to mood variability were mixed: For some items, we found stronger reductions in state variability in the NRT group, whereas for other items, the decline in variability appeared to be equal in both groups or even stronger in the Placebo group.
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