By Emma Young
If I had to choose between giving up alcohol or coffee, it would have to be alcohol. I just love coffee too much… But do I, really? Or do I just want it, which is different?
Despite being the most widely used psychoactive drug in the world, there’s ongoing debate about just how addictive caffeine is. It does share some of the criteria for dependence: regular users who skip their morning cup will often report withdrawal symptoms, such as headaches, for example. “Caffeine use disorder” is even being discussed for potential inclusion in the next edition of the Diagnostic and Statistical Manual of Mental Disorders. But is it really addictive in the same fundamental way as a harder drug like cocaine?
A new paper published in the Journal of Psychopharmacology suggests that it is. Nicolas Koranyi at the University of Jena, Germany, and colleagues found that heavy coffee drinkers want coffee a lot more than they like it. The implication is that they drink it mostly or entirely to feed their addiction, rather than for pleasure.
Typically, as someone develops an ever stronger dependence on an addictive drug, they come to want it more, as brain networks involved in motivation become more sensitised, but to like it less. The team figured that this was, then, a useful framework in which to explore attitudes to coffee.
It’s not reasonable, though, just to ask people how much they want or like coffee, the team decided. They might easily confuse the two, and not know the answer. So the team designed a study to tap into the participants’ implicitly held associations between coffee and wanting or liking.
Fifty-six German students took part. About half were “heavy” coffee drinkers, who consumed three or more cups per day. The rest either didn’t drink coffee or had no more than one cup a day. The participants first reported on their levels of coffee-related complaints, such as withdrawal symptoms. Then they embarked on the computer-based assessment.
In the “liking” component of the study, participants saw a series of pictures of coffee and juice, interleaved with other trials in which they saw positive or negative pictures (e.g. puppies or human skulls). They had to use two keys on the keyboard to quickly indicate whether a given picture was either coffee or juice, or whether it was “pleasant” or “unpleasant”. For instance, during part of the experiment the right hand key was used to indicate that a picture was of coffee, but also to indicate that a picture was pleasant. This mapping changed during the experiment. Simply put, by comparing the speed of participants’ responses when “coffee” and “pleasant” pictures shared a key to when “coffee” and “unpleasant” pictures shared a key, the researchers could explore the extent to which they implicitly liked coffee.
In the “wanting” component, participants again had to rapidly sort a series of coffee and juice images, this time indicating whether they were “wanted” or “not wanted”. Again, these were interspersed with other trials, this time displaying either a letter or a number. Participants had to respond with the “I want” key for numbers, and if their response was correct they would get a small amount of money. If they saw a letter, they had to respond “I do not want”. These trials gave an indication of how much participants implicitly wanted coffee .
(It’s worth noting that this kind of task, known as the Implicit Association Test, has come under criticism in the past. However, in previous work, some of the authors of this new study have argued that the test holds enormous potential, if used properly. And in this study, it was not used in the same way as in controversial research to supposedly explore implicit racism, for example.)
The results revealed that heavy drinkers had a strong wanting for coffee — much more than the light drinkers. But both heavy and light drinkers showed a similarly low liking for coffee. “To our knowledge, the findings… provide the first demonstration of a dissociation between wanting and liking for coffee for heavy coffee drinkers,” the researchers report. And this suggests that caffeine should indeed be placed in the same group as alcohol, cocaine and amphetamines, in affecting brain systems involved in motivational, wanting processes.
Caffeine likely has a much weaker effect on this system than those other drugs. “However, with regard to the underlying motivational and neurophysiological processes involved in dependence development, the main difference between highly addictive drugs (eg alcohol or cocaine) and substances with lower addictive strength (eg caffeine) may be mainly a quantitative than a qualitative one,” the team concludes.
As someone who typically drinks two cups of coffee each morning, I don’t meet the team’s “heavy user” definition. No matter how much I want it, I also know that I like it — especially a great cup. My favourite local cafe can’t re-open too soon…