Coffee linked to slower biological ageing among those with severe mental illness

Is it possible that this phenomenon is specific to people with those mental illnesses? A wider general population study resulted in the inverse effect:

https://www.mdpi.com/2072-6643/15/6/1354

I only did a postgraduate degree, so I don't have the practice reading scientific studies to determine which is true. Maybe someone with more knowledge can chime in?

Separately from this study, here's an interesting opinion piece by John Ioannidis titled "The Challenge of Reforming Nutritional Epidemiologic Research", published in JAMA 2018:

https://statmodeling.stat.columbia.edu/wp-content/uploads/20...

  > Assuming the meta-analyzed evidence from cohort
  > studies represents life span–long causal associations, for
  > a baseline life expectancy of 80 years, eating 12 hazelnuts
  > daily (1 oz) would prolong life by 12 years (ie, 1 year per
  > hazelnut), drinking 3 cups of coffee daily would achieve
  > a similar gain of 12 extra years, and eating a single man-
  > darin orange daily (80 g) would add 5 years of life. Con-
  > versely, consuming 1 egg daily would reduce life expec-
  > tancy by 6 years, and eating 2 slices of bacon (30 g) daily
  > would shorten life by a decade, an effect worse than
  > smoking. Could these results possibly be true?

via Andrew Gelman's blog: https://statmodeling.stat.columbia.edu/2019/01/26/article-po...

these things are 100% true. I eat one hazelnut per hour and have lived already 230 years.