About 20 years ago our society gained a deep understanding of the notion of
causality. (To learn more, search the web for "Judea Pearl".) According to the
terminology standardized at that time, yes, if adding particulate pollution to the air makes it more likely that a person breathing that air is depressed, then that is a casual link or a cause-and-effect relationship. It might be the case however that polluting the air reduces the person's quality of life and that if it were possible to effect an identical reduction of quality of life without polluting the air, then polluting the air would have no further effect on the likelihood of depression. if that is the case, we say that quality of life "screens off" the effect of air pollution on depression.
