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?

It's well-known that schizophrenics self-medicate with coffee and nicotine: https://en.wikipedia.org/wiki/Schizophrenia_and_tobacco_smok...

The inverse possibility--that nicotine, and perhaps caffeine as well, heighten the risk of psychosis in those genetially predisposed--has also been considered.

Not diagnosed, but eventually I noticed how veggies gave me psychotic episodes that would last for a few days. Was connected to oxolates seemingly. After one week of probiotics psychosis doesn't happen when I eat veggies now.

Incidentally caffeine calms me down as well.