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Open WellbeingWhat the studies actually measured

Mood, stress and thinking

Caffeineand Anxiety

Only one source here so far, and it measured higher anxiety.

How sure anyone can be

Moderate certainty, level 3 of 4

Further research may change this.

The numbers reported

No number has been put on this yet. One source recorded only which way the numbers went — for now, that is all we have here.

One source, newest first

What we read is the published abstract, not the full paper, so a blank below may still be printed in the paper itself. A fixed rule worked this out from the source’s own fields. Nobody checked this rating by hand.

  • Systematic review, 2026

    Moderate certainty, level 3 of 4

    The Effects of Caffeine on Anxiety Behavior in Healthy Individuals: A Systematic Review of the Literature.

    Stress Health. 2026;42(1):e70139. doi:10.1002/smi.70139. PMID:41549915.

    Number reported
    Not in the abstract
    Which way it went
    Higher
    Likely range
    Not in the abstract
    Source’s own words
    anxiety symptoms vs the included comparators; the abstract prints direction, not a pooled magnitude
    Who was studied
    Healthy individuals
    Compared with
    not stated in the abstract
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    Not in the abstract
    Kind of record
    Journal article
    How this rating was reachedstarts at High, one step down: imprecision
    1. Starts at High
    2. Imprecision brought it down to Moderatethe abstract reports no confidence interval for the estimateNot in the abstract
    3. Ends at ModerateOne step down.
    Checked, nothing to step it down for
    risk of bias and indirectness
    Inconsistency
    No disagreement reported, and no count of studies behind it

    Imprecision stops at the first check that applies; others may apply too.

    Source saved; quote checked byte-for-byte against it by software; no signature.

    Read the abstract on PubMed

What is still missing from these readings

  • No number at all, only which way it went.
  • One gives no likely range, so how precise that number is is unknown.
  • One do not say how many people took part.
  • Amount taken — Not in the abstract.
  • For how long — Not in the abstract.

Something nobody wrote down is never a zero and never a guess.

Still to read for Caffeine

Eight of the 19 things on our list for Caffeine have no reading here yet:

  • Cognitive performance
  • Estimated VO2max
  • Fatigue
  • Heart rate variability (RMSSD)
  • Light sleep
  • Number of awakenings
  • Resting heart rate
  • Serum cortisol (morning)

Still to read means nobody here has got to it, not that it was tried and did nothing or that no research exists. A pairing on no list is not a gap: we never set out to read it.

Read next

This is a library, not advice. No recommendation, no dose, no diagnosis, no ranking. We never ask about your symptoms, and nothing here is tailored to you.