Those jittery people who suspect their decaf coffee has been laced with that demon caffeine are right.

University of Florida researchers have found that the decaffeination process doesn’t eliminate caffeine but merely reduces the levels of the stimulant.

Test samples from 10 US chains and local coffee houses in Florida showed that a large decaf could contain 8.6mg to 13.9mg of caffeine. The same cup of regular coffee has 170mg.

“If someone drinks five to 10 cups of decaffeinated coffee, the dose of caffeine could easily reach the level present in a cup or two of caffeinated coffee,” Bruce Goldberger, co-author of the study, told the journal Preventive Medicine Week.

Many people choose decaffeinated coffee for medical reasons, ranging from sleep disorders to anxiety to elevated blood pressure.

Dr Goldberger said those sensitive to even the slightest levels of caffeine might want to lay off coffee altogether and try herbal tea, which was completely caffeine-free.