Critical Reasoning

A study followed a group of teenagers who had never smoked and tracked whether they took up smoking and how their mental health changed. After one year, the incidence of depression among those who had taken up smoking was four times as high as it was among those who had not. Since nicotine in cigarettes changes brain chemistry, perhaps thereby affecting mood, it is likely that smoking contributes to depression in teenagers.

Which of the following, if true, most strengthens the argument?

A. Participants who were depressed at the start of the study were no more likely to be smokers after one year than those who were not depressed.

B. The study did not distinguish between participants who smoked only occasionally and those who were heavy smokers.

C. Few, if any, of the participants in the study were friends or relatives of other participants.

D. Some participants entered and emerged from a period of depression within the year of the study.

E. The researchers did not track use of alcohol by the teenagers.

OA later. Thanks guys!

A?

B - Weakens
C - Who cares
D - Weakens
E - Who cares

IMO D.

A. Weakens
B. smoking is smoking, be it occasional or heavy and smoking would have caused depression.
C. it might imply passive smoking , bu there is no mention of it and we are not sure whether they are smokers or not.
E. Effect of alcohol is not in the argument.

what is the OA ?

spring

A - It is not mentioned that whether the participants who were depressed at the beginning of the study were not depressed at the end of the study.

OA: A. Thanks all

What is the general concept tested in such problems?>
My understanding:
To infer that A causes B, we should be sure that B was not the cause of A.

e.g. To conclude that Smoking causes depression, we should be sure that it was not depression that caused smoking. As in a grp of guys, we see a subgroup that is smoker as well as depressed so we need to differentiate what cause what.

Is that correct?

I think A is the right answer here

Simply put A states that all were equally likely to be smokers.

The possibility that the ones depressed at the start were no more likely to be smokers than those who were not depressed; ie all were equally likely strengthens the argument.