This kind of stuff drives me nuts

All around in health news, are headlines like this: "Smoking Increases Risk of HIV Infection."

But when you read the information on the study, all it does is show that many people who get HIV are smokers, which shouldn't suprise anyone. Why? Because one of the largest factors in smoking is having children, and people generally at risk for HIV infection don't have kids and aren't trying to have kids.

The article I link above even points it out, yet they still run the headline, I guess for the shock value.

The consistency of the findings is striking and represents a major strength of this review," Dr. Furber and colleagues said, noting that while the studies vary, many had large sample sizes and were of high quality.


On the other hand, the researchers said, the methodologies used -- epidemiological and observational -- can't make causal connections and are "prone to confounding."

So there isn't a causal relationship, and saying 'increases risk' would be, well, incorrect.