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Open WellbeingWhat the studies actually measured

Mood, stress and thinking

Iodineand Cognitive performance

Two sources here, and they say different things: one measured higher cognitive performance and one found no clear difference.

How sure anyone can be

Low certainty, level 2 of 4

Further research is likely to change this.

The most certain of the two findings here; each record carries its own.

The numbers reported

One source’s range, drawn against its own line of no difference and scaled to its own numbers.

0.10.27 standardised effect size0.44

This range stays on one side of the no-difference line.

Bar the confidence interval — the range the true effect is likely to sit inNotch the number the source reportedLine where there would be no difference at all

Two sources, newest first

We do not pick between these or average them into one number.

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, 2020

    Very low certainty, level 1 of 4

    Systematic review and meta-analysis of the effects of iodine supplementation on thyroid function and child neurodevelopment in mildly-to-moderately iodine-deficient pregnant women.

    Am J Clin Nutr. 2020;112(2):389-412. doi:10.1093/ajcn/nqaa071. PMID:32320029.

    Number reported
    -0.18
    Which way it went
    No clear difference
    Likely range
    -1.22 to 0.87
    Source’s own words
    mean difference in child cognitive score vs control
    Who was studied
    Pregnant
    Compared with
    placebo or no supplement
    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, 3 steps down: risk of bias, indirectness and imprecision
    1. Starts at High
    2. Risk of bias brought it down to Moderatethe abstract reports no risk-of-bias or quality appraisal, so study limitations cannot be ruled outNot in the abstract
    3. Indirectness brought it down to Lowthe outcome measured is a proxy for the target outcomeReported in the abstract
    4. Imprecision brought it down to Very lowthe confidence interval includes no effectReported in the abstract
    5. Ends at Very low3 steps down.
    Inconsistency
    No disagreement reported, and no count of studies behind it

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

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

  • Systematic review, 2014 · 2 studies pooled

    Low certainty, level 2 of 4

    Therapy of endocrine disease: Impact of iodine supplementation in mild-to-moderate iodine deficiency: systematic review and meta-analysis.

    Eur J Endocrinol. 2014;170(1):R1-R15. doi:10.1530/EJE-13-0651. PMID:24088547.

    Number reported
    0.27 standardised effect size
    Which way it went
    Higher
    Likely range
    0.1 to 0.44
    Source’s own words
    standardised mean difference, global cognitive index
    Who was studied
    Child
    Compared with
    placebo or no supplement
    Amount taken
    Not in the abstract
    For how long
    Not in the abstract
    Disagreement between studies
    significant heterogeneity between studies
    Kind of record
    Journal article
    How this rating was reachedstarts at High, 2 steps down: risk of bias and imprecision
    1. Starts at High
    2. Risk of bias brought it down to Moderatethe abstract reports no risk-of-bias or quality appraisal, so study limitations cannot be ruled outNot in the abstract
    3. Imprecision brought it down to Lowthe abstract does not state how many participants were pooledNot in the abstract
    4. Ends at Low2 steps down.
    Checked, nothing to step it down for
    indirectness
    Inconsistency
    No high disagreement reported between the 2 studies it pooled

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

    AI-reviewed & signed — an AI agent re-read this finding against the saved source and checked that the quote, the numbers, the units and the direction match it. No person read it. The owner authorised the agent to sign the batch with the owner's key, and every build rechecks that signature against these exact bytes.

    Read the abstract on PubMed

What is still missing from these readings

  • Two 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 Iodine

One of the six things on our list for Iodine has no reading here yet:

  • Iodine, Serum

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.