Conclusions: While a linear association between any social class indicator and psychological distress was observed in the US, the association between subjective social class and psychological distress seems U shaped in Japan, probably reflecting the fact that those with high education or low income had a higher prevalence. Background. Despite a number of papers on the FCTC negotiation process and final text, there have not been attempts to test the usefulness of treaty process by quantifying its global impact on the adoption of domestic tobacco control policies. This paper suggests that the negotiation process provided a platform for increased communication and international learning through which tobacco control information spread to many countries; and that this simultaneous learning process accelerated the adoption of internationally promoted tobacco control policies by countries around the world.