The association between high nicotine dependence and severe mental illness may be consistent across countries.

Abstract
Studies all over the world suggest that severe mental illness, including schizophrenia and mood disorders, is associated with tobacco smoking. This study, combining samples from the United States and Spain, had 3 objectives: (1) to test the hypothesis that severely mentally ill patients who smoke are more likely to have a high nicotine dependence when compared with control smokers, (2) to compare frequencies of high nicotine dependence in controls in both countries, and (3) to compare frequencies of high nicotine dependence in severely mentally ill patients in both countries.