Out of 300 students, a quarter said they experienced upset stomach, anxiety, headaches and trouble sleeping from it.
Massey professor Ajmol Ali worked on the study and said he could guess why people weren’t giving it up so easily.
“If you’ve got a good relationship with someone, there might be some things that are not so good... but you feel the relationship is still strong because it does these things for you.”
The ‘safe’ level of caffeine is deemed to be 400 milligrams a day, and 14 percent of students regularly topped this.
Some respondents had up to 1988.14 milligrams in a day – the equivalent of nine double-shot flat whites.
The University of Canterbury wasn’t part of the sample but a post on a student Facebook page suggested they needed it to stay awake in lectures. Some felt it heightened anxiety, while some felt it soothed it.
University student Josh Boulton said he was a “recovering coffeeholic”, having quit it a few days ago.
He said he was sleeping better and felt more clear-headed, but this wasn’t the first time he’d had to quit.
Boulton said coffee gave him a reward response and he felt unstoppable after a cuppa, but because of this he found himself having a bit too much.
Another student George Hampton said he took a litre of strong black coffee to uni every day, the only noticeable effect was shaky hands.
Ali said everyone had different levels of enzymes in their liver that break down caffeine; some have more and can metabolize it really quickly, but for those with less, coffee at 5pm can mean a sleepless night.
He said if you're experiencing bad side effects, quitting cold turkey could be dangerous. Coffee drinkers should look at lowering the number of cups per day or brewing it slightly weaker, he said.
He hoped to provide some caffeine literacy, so people could make informed decisions about their habits.