Comment Patients with dementia don't seek cataract surgery (Score 1) 70
People trot out the whole "correlation isn't causation" thing as if to suggest that finding correlations is useless and misguided: it is not. it is an excellent way to find possible causes. In this case though, there is a more simple reason for the observed correlation. It isn't that improved eyesight improves mental health, but rather that if you are developing dementia you are less likely to seek out treatment for declining eyesight ( i.e it isn't "seek cataract surgery" => NOT dementia, but instead dementia => NOT "seek cataract surgery"
There was a "Viagra cures Alzheimer's" story just yesterday that is he same thing. The more boring and more likely reason for the correlation is that Alzheimer's patients don't ask for Viagra