The media absolutely gushed over the possibility that smoking leads to brain damage, highlighted in a 'study' Monday. They were so happy to not have to write about another miracle vegetable or marshmallow cannons and call it 'science' they didn't bother to really read the data, so the news coverage of the study was misleading and highlighted why we need better science journalism.
They didn't bother to note that the study was observational, they only examined "... the association between smoking history and cognitive decline in the transition from midlife to old age." Participants reported their own smoking habits spanning a period of 25 years. Self-reported data like this can be problematic because there are no controls in place. People can easily misreport how much they smoke in either direction. Additionally, as the authors themselves admit, the data "... cannot be assumed to be representative of the general population," because the participants were white-collar civil servants.
Smoking Causes Brain Damage? Why We Need Better Science Journalism by Cameron English, Policy Mic
Science Journalism: Less Gushing, More Analysis, Please