Discussion
CURB
In this study, unlike any of the related earlier studies in Turkey, a survey-based experiment was used to randomly assign participants to control and treatment groups (eliminating the bias due to self-selection into groups), with the aim of estimating the differential effects of PP and GHWs on three outcome variables. It was found that among university students PP and stronger GHWs were effective in generating negative affect and avoidant responses among ever-smokers of cigarettes, in a setting where almost all of the participants were aware that smoking cigarettes is harmful to health. Earlier studies have reported similar findings for PP [At the time of the switch to PP, Turkey replaced the old GHWs on cigarette packs with new and stronger ones; therefore, it is important to disentangle the two effects [Comparisons of average intention to quit across experimental conditions showed that the disentangled differential effects of PP and stronger GHWs on intention to quit were statistically zero. This implies that further measures and tools are necessary for effective tobacco control. The findings in the related literature are mixed [It is noteworthy that the differential effect of GHWs (relative to text-only warnings) (condition 1 versus 2) was small on negative affect and statistically zero on the other two outcome variables. Such a finding was unexpected in light of earlier studies [The results of this study should be interpreted in light of several limitations: Our sample was a convenience sample with participants recruited from four universities; hence, it may not be representative of university students in the country. The studied effects of package design elements may vary in the other cities of Turkey. Moreover, the cross-sectional nature of the data prevents us from interpreting the findings in a causal sense and observing behavioural changes over time. Another limitation is that, although participants could observe the images as long as they wanted, they viewed the packages on a screen rather than in hand; the effects of actual interaction may be different.Another aspect of the PP regulation in Turkey was the choice of the black colour for the background, rather than the dark brown or dark green colour used in other countries. It is unknown whether and how the estimated effects in this study would change if the background were not black but another dark colour as in the other countries.Despite these limitations, this study can motivate future quantitative and qualitative research to better understand the emotional impact of PP and GHW regulation and, equally importantly, any changes in the behaviour it generates. This can guide regulatory efforts to curb smoking during the critical years of tertiary education.