If one's research question is: "Does X have a causal effect on Y?", there are some obvious questions that one would ask before interpreting an observed association causally. For example, "Is there something unmeasured that affects both X and Y?". Among the most obvious of these preliminary questions is: "Does Y in fact cause X?" This would be especially salient in a cross-sectional study, which is why there is so much emphasis put on the term "prospective" in reporting designs that are NOT cross-sectional.
So if that is so painfully obvious that it would be embarassing to even mention it again, why does one read reports like this one on a daily basis? The headline is:
Obese teens' brains unusually susceptible to food commercials, study finds
and the summary text below the headline is:
TV food commercials disproportionately stimulate the brains of overweight teenagers,
including the regions that control pleasure, taste and -- most surprisingly -- the mouth,
suggesting they mentally simulate unhealthy eating habits that make it difficult to lose
weight later in life.
The study conducted fMRI exams on 40 right-handed adolescents, 20 normal weight and 20 obese, so everything is cross-sectional.
The discussion reveals an interpretation clearly in the causal direction that being obese makes your brain more susceptible to food commercials:
Collectively, these findings suggest that higher-adiposity adolescents more strongly recruit
oral somatomotor and gustatory regions pertinent to eating behaviors while viewing food
commercials, in comparison with their lower-adiposity counterparts.
How is it that none of these study authors with doctoral degrees seems to have ever wondered how these children got to be obese in the first place?
So if that is so painfully obvious that it would be embarassing to even mention it again, why does one read reports like this one on a daily basis? The headline is:
Obese teens' brains unusually susceptible to food commercials, study finds
and the summary text below the headline is:
TV food commercials disproportionately stimulate the brains of overweight teenagers,
including the regions that control pleasure, taste and -- most surprisingly -- the mouth,
suggesting they mentally simulate unhealthy eating habits that make it difficult to lose
weight later in life.
The study conducted fMRI exams on 40 right-handed adolescents, 20 normal weight and 20 obese, so everything is cross-sectional.
The discussion reveals an interpretation clearly in the causal direction that being obese makes your brain more susceptible to food commercials:
Collectively, these findings suggest that higher-adiposity adolescents more strongly recruit
oral somatomotor and gustatory regions pertinent to eating behaviors while viewing food
commercials, in comparison with their lower-adiposity counterparts.
How is it that none of these study authors with doctoral degrees seems to have ever wondered how these children got to be obese in the first place?
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