The authors admit this in the paper. They write: "This is a cross-sectional study, which only allows us to identify associations, not causal relationships."

The methods of the study were as follows: "Individuals were recruited at e-cigarette retail locations in a large metropolitan city in the midwestern portion of the United States in July 2013. A total of 159 participants completed a brief 29-item self-report measure that assessed behaviors and perceptions of use."

LAST：Glass 1.6ml airflow adjustable tank oniyo 1.0 e cigarette atomizer |NEXT：best vape pen glass globe vaporizer wax atomizer atomizer exgo