Smokers are less likely than nonsmokers to report experiencing positive emotions, and also less likely to say they're treated with respect. Gallup has found that one in four Americans have less respect for smokers, and this social disapproval may negatively affect how smokers actually are treated or how they perceive they're treated.

Researchers noted it isn't clear whether experiencing these negative emotions leads people to start or continue smoking, or whether the act of smoking makes smokers more likely to report experiencing these negative emotions.

Poor emotional health comes despite smokers' income level.

"This means that socioeconomic status alone does not account for the differences in emotional health between smokers and nonsmokers; rather there is something else about being a smoker that relates to having worse emotional health," the report notes.

Smoking rates continue to decline in the United States, with 19.1 percent of Americans currently reporting that they smoke. Still, smoking continues to be a costly problem. According to the CDC, smoking-related illness in the U.S. costs $96 billion in medical costs and $97 billion in lost productivity each year.

Gallup's findings are based on more than 83,000 interviews conducted Jan. 3-June 18 collected as part of the Gallup-Healthways Well-Being Index.