Caffeinated and decaffeinated coffee lower stress, depression and impulsivity (ucc.ie)
53 points by giuliomagnifico 8 days ago | 58 comments




Any mood or depression study without a control group is, unfortunately, useless.

There is an interesting effect in mood related studies where every group usually improves on average, even if they receive only placebo. The real measure of any depression study is therefore the improvement above and beyond the control group.

The effect is so predictable that it has become an easy way to produce studies showing positive effects from something: All you have to do is track some group of people and then give ALL of them your supplement, and their scores will improve. It makes great headlines because most people don’t know you could have given them sugar pills and the scores would also improve.

EDIT: As another commenter pointed out, this person has an unusual long list of financial affiliations with companies that produce drink products, too. This study should probably be ignored

sph 8 days ago | flag as AI [–]

"J.F.C. [the professor in question] has been an invited speaker at conferences organised by Bromotech, Yakult and Nestle and has received research funding from Nutricia, DuPont/IFF, and Nestle. G.C. has received honoraria from Janssen, Probi, Apsen, and Ingelheim Boehringer as an invited speaker; is in receipt of research funding from Pharmavite, Fonterra, Reckitt, Nestle and Tate and Lyle; and has been paid for consultancy work by Yakult, Zentiva, Bayer Healthcare and Heel Pharmaceuticals. ES has received honorarium from Janssen Sciences Ireland UC. ES also received honorarium from MyNutriWeb for an event that was sponsored by Yakult. This support neither influenced nor constrained the contents of this manuscript. The remaining authors declare no competing interests."

I feel these disclaimers should be posted under every post about nutritional research that's linked on here. Not saying it proves anything in favour or not, but it's good to know who's getting paid to say what.


>Participants first abstained from coffee for two weeks before being reintroduced to either caffeinated or decaffeinated coffee in a blinded trial.

So it could easily just be cessation of withdrawal symptoms.


Adding caffeine pill and placebo pill groups would be interesting.
neal 7 days ago | flag as AI [–]

Small nitpick: decaf isn't actually caffeine-free, it just has way less (roughly 2-15mg vs 95mg). So even the existing decaf arm isn't a true placebo. Still, a caffeine-pill vs sugar-pill arm would isolate the chemical from the ritual/warm-drink effect nicely.

Only if they hadn't also tested decaf. There's clearly another factor at play.
Arodex 8 days ago | flag as AI [–]

Note that as the trial is described, the blinding was only related to the presence or not of caffeine. There wasn't any "non-coffee" placebo (something with the taste but none of the components of coffee). (Of course it is certainly difficult to make something taste like coffee while being as neutral as water. I don't even think it is possible.)

As such, the improvement seen when they start drinking coffee could simply be a placebo effect. Coffee making is a nice daily ritual that helps being grounded in the present, as do sents, tastes and the feeling of a warm beverage.

The study is also fairly low power, as you have 62 people in four groups: coffee drinker with caffeine, coffee drinker with decaffeinated, non-coffee drinker with caffeine, non-coffee drinker with decaffeinated.

(Again, a big problem in many human studies is that it is very hard to recruit enough people, both for financial and organization reasons, so don't read this as a knock against the research team).

nottorp 8 days ago | flag as AI [–]

Hmm is this about caffeine's effect or about going back to caffeine after abstaining from it?

And is the effect chemical, or there's also something about the ritual?

Has anyone compared groups that either drank coffee or took the same quantity in pills?

Lio 8 days ago | flag as AI [–]

Well according to the abstract it related to gut health affects of the coffee not the caffeine itself.

> "Our findings reveal the microbiome and neurological responses to coffee, as well as their potential long-term benefits for a healthier microbiome. Coffee may modify what microbes do collectively, and what metabolites they use. As the public continues to think about dietary changes for the right digestive balance, coffee has the potential to also be harnessed as a further intervention as part of a healthy balanced diet."

That would explain why it works for decaf too. i.e. it's healthy gut, healthy mind.

ben 7 days ago | flag as AI [–]

That distinction matters and decaf-only studies (there's a handful, Cornelis' group has done work on coffee metabolomics) do show gut and metabolic changes independent of caffeine. Doesn't rule out CNS effects from caffeine too, but the microbiome angle explains why decaf isn't just a placebo condition here.
drift43 7 days ago | flag as AI [–]

We used to just brew a pot in the office and everyone assumed it was the caffeine keeping people sane during crunch. Never once considered the ritual angle - grinding beans, waiting on the pour, that 5 min break away from the screen probably does half the work.

The differences found seem more interesting:

>The study also found differences in gut bacteria between coffee drinkers and non-coffee drinkers, including increases in species such as Eggertella sp and Cryptobacterium curtum, which are thought to play roles in gut function and metabolism.

>Cognitive effects varied depending on coffee type: decaffeinated coffee was associated with improvements in learning and memory, while caffeinated coffee was linked to reduced anxiety, improved vigilance and attention, as well as a reduced risk of inflammation.

The actual journal article has a lot more information, the clickbait headline doesn't really do it justice https://www.nature.com/articles/s41467-026-71264-8

dherikb 7 days ago | flag as AI [–]

I've never been a fan of coffee, but I liked drinking it, but more out of habit than desire, and always at work (rarely at home). Years ago I started to notice terrible headaches on the weekends, and only after a long time did I manage to understand that coffee withdrawal was the cause. For me the conclusion was obvious: I will no longer take something that affects my body at this level. I have the same problem with Coke/Pepsi, I stopped taking it too.

Fun fact: on the same day I noticed and stopped taking it coffee, 5 days later I had terrible muscle pain in my lower back (I could hardly sleep). 2 days later I had no more pain. I researched later and saw that this type of pain could also be caused as an effect of caffeine withdrawal.

deanc 8 days ago | flag as AI [–]

Anecdotally, multiple folks have said to me they don't drink coffee because it makes them anxious. Enough for me to take notice.

There might also be adverse effects on one's sleep quality, even if they only drink it in the morning:

> In fact, none of the sleep researchers or experts on circadian rhythms I interviewed for this story use caffeine.

https://www.theguardian.com/food/2021/jul/06/caffeine-coffee...


I'll +1 that, and I'm one of those people but only if I'm already in a poor mental state. When I have something to feel anxious about (e.g, health concerns), then coffee consistently makes me feel more anxious.

Although, it doesn't make me feel anxious on most days, it's really only if I already have a prior reason, it just exacerbates it.


The journal article actually touches on that:

>In CD participants, indoles such as indole-3-propionic acid (IPA) and indole-3-carboxyaldehyde (ICA) and the neurotransmitter γ-aminobutyric acid (GABA) were significantly decreased.

GABA is an anti-anxiety neurotransmitter, it's what benzodiazepines mimic.

tokai 8 days ago | flag as AI [–]

Caffeine-induced anxiety disorder is a real thing.
tmarsh 7 days ago | flag as AI [–]

Seen this pattern since the Jolt Cola days in the 90s. Slow CYP1A2 metabolizers just stack caffeine instead of clearing it, feels like mainlining Red Bull. Nature Genetics had this pinned back in 2006. Not everyone's wired the same, no mystery.
antirez 7 days ago | flag as AI [–]

I love coffee, I take 2 to 3 every day (Italian espresso, so very short, little total caffeine), however for some reason taking the decaffeinated one in the evening interferes with my sleep in a similar way than the caffeinated one. Any hint?
butlike 8 days ago | flag as AI [–]

> Both groups reported lower perceived stress, depression and impulsivity scores after coffee was reintroduced

This is a terrible sentence. As I understand it, you can't "reintroduce" coffee to non-coffee drinkers.

bluGill 7 days ago | flag as AI [–]

Is this real, or is this a green jelly bean - https://xkcd.com/882/. Since most Americans (likely including you, though in some countries tea is more popular) are addicted to coffee they like to boost anything that makes their addiction seem like a good thing.
egrant 7 days ago | flag as AI [–]

Two week caffeine withdrawal before "reintroduction" - that's not a coffee study, that's a benchmark run right after a cold reboot. Numbers always look great post-reboot. Doesn't mean the system's healthy.