For some, there's no escape from the daily grind .

According to a study in the Journal of Caffeine Research, the negative effects of caffeine can go unrecognised, and cases of problematic caffeine use may call for treatment. The study summarised the results of previously published caffeine research and found that more than half of regular caffeine consumers report difficulty quitting or reducing caffeine use. Study co-author Laura Juliano advises that healthy adults should limit caffeine consumption to no more than 400mg per day, or about two to three 240ml cups of coffee. Pregnant women should consume less than 200mg per day. 

Jeanette Wang (jeanette.wang@scmp.com)