BACKGROUND AND AIMS There is a longstanding assumption that cigarette smoking stabilizes mood. However, no studies have rigorously evaluated mood stability as people progress from occasional to regular use of tobacco cigarettes. This observational study thus tested two central questions: as smoking rates increase, (1) does the acute mood boost after smoking become more stable and (2) do background moods (i.e. mood levels outside of smoking) become more stable?

DESIGN, SETTING AND PARTICIPANTS Observational study of a cohort of n = 255 youth enriched for current smoking (mean age at baseline = 15.63 years, 52% female, 67% non-Hispanic White) recruited from 16 high schools in or near Chicago, Illinois, USA. They participated in up to 6 waves of ecological momentary assessment (EMA) spanning 6 years of their adolescence and young adulthood. During each week-long EMA wave, youth self-initiated reports of mood levels immediately before and after smoking. They also reported on background mood levels in response to random prompts ~5 times/day.

MEASUREMENTS Mixed-effects location scale (MELS) modeling tested the effects of within-person smoking rates on within-person variability in positive affect (PA) and negative affect (NA) levels modeled (1) from before to after smoking and (2) outside of smoking.

FINDINGS As smoking rates increased, on average, variability decreased by approximately 15-20% in the heightened PA (P < 0.01) and diminished NA (P < 0.01) changes from before to after cigarette use. Gender moderated the associations between smoking rates and mood variability during background random, non-smoking times: as smoking rates increased among boys only, on average, variability in background PA (P < 0.01) and NA (P < 0.01) decreased by around 10%.

CONCLUSIONS As youth progress from occasional to more frequent cigarette use, their immediate mood boost after smoking appears to become more stable. Among boys only, background moods outside of smoking also appear to stabilize.