Study links three to four cups of coffee with slower aging marker

Three to four cups of coffee a day were tied to longer telomeres in adults with severe mental illness, a result that researchers say points to a biological aging marker, not a proof that coffee slows aging.

The study, published in BMJ Mental Health on Nov. 25, 2025, analyzed 436 adults from Norway’s Thematically Organised Psychosis study, including 259 people with schizophrenia spectrum disorders and 177 with affective disorders such as bipolar disorder and major depressive disorder with psychosis. Researchers measured telomere length in leukocytes from blood samples using quantitative real-time PCR, then compared those results with reported coffee intake split into no coffee, one to two cups, three to four cups, and five or more cups per day.

The pattern was an inverted J-shape. Telomere length peaked in the three-to-four-cup group, and the largest gap was between that highest recommended coffee group and non-drinkers. In the study’s adjusted models, people drinking three to four cups daily had telomere lengths comparable to a biological age about five years younger than people who drank no coffee. The same benefit did not continue past four cups a day.

That finding stands out because severe mental disorders already carry a heavy health burden. King’s College London says people with severe mental illness have an average life expectancy about 15 years shorter than the general population, and the BMJ paper notes that individuals with severe mental disorders tend to have shorter telomeres than the general population. In that context, even a modest association with a biological aging marker is attention-grabbing, especially for a population facing elevated risk of age-related disease.

Still, the authors were clear about the study’s limits. This was a cross-sectional analysis, so it captured a snapshot in time and cannot show that coffee caused the telomere differences. The researchers controlled for age, sex, ethnicity, tobacco use, diagnosis type, medication and other factors, but the result remains an association. The BMJ Group press release also noted that about 77% of participants were smokers, and those drinking five or more cups a day had smoked for significantly longer, which makes interpretation harder.

The researchers pointed to a few possible explanations, including coffee’s antioxidant and anti-inflammatory compounds and a potential reduction in oxidative stress. Vid Mlakar said coffee is a daily beverage and that excessive intake can harm sleep quality, even if intake up to a certain point may have benefits for biological aging. The dose line also fits existing caffeine advice: the NHS limit cited in the paper is 400 mg a day, roughly four cups of coffee, and the FDA says that amount is generally not associated with dangerous negative effects for most healthy adults.