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Effect size, IQ and

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  • Morten Hesse
    Concerning the difference in IQ between those breastfeeded and those not: the effect size in this study is over half a standard deviation . Half a standard
    Message 1 of 2 , Oct 31, 2006
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      Concerning the difference in IQ between those breastfeeded and those
      not: the effect size in this study is "over half a standard
      deviation". Half a standard deviation corresponds to r=0.2425. That's
      a big effect size. However, look at the summary below:

      BMJ. 2006 Oct 4; [Epub ahead of print]Click here to read Links
      Effect of breast feeding on intelligence in children: prospective
      study, sibling pairs analysis, and meta-analysis.

      * Der G,
      * Batty GD,
      * Deary IJ.

      MRC Social and Public Health Sciences Unit, Glasgow G12 8RZ.

      OBJECTIVE: To assess the importance of maternal intelligence, and
      the effect of controlling for it and other important confounders, in
      the link between breast feeding and children's intelligence. DESIGN:
      Examination of the effect of breast feeding on cognitive ability and
      the impact of a range of potential confounders, in particular maternal
      IQ, within a national database. Additional analyses compared pairs of
      siblings from the sample who were and were not breast fed. The results
      are considered in the context of other studies that have also
      controlled for parental intelligence via meta-analysis. SETTING: 1979
      US national longitudinal survey of youth. SUBJECTS: Data on 5475
      children, the offspring of 3161 mothers in the longitudinal survey.
      MAIN OUTCOME MEASURE: IQ in children measured by Peabody individual
      achievement test. RESULTS: The mother's IQ was more highly predictive
      of breastfeeding status than were her race, education, age, poverty
      status, smoking, the home environment, or the child's birth weight or
      birth order. One standard deviation advantage in maternal IQ more than
      doubled the odds of breast feeding. Before adjustment, breast feeding
      was associated with an increase of around 4 points in mental ability.
      Adjustment for maternal intelligence accounted for most of this
      effect. When fully adjusted for a range of relevant confounders, the
      effect was small (0.52) and non-significant (95% confidence interval
      -0.19 to 1.23). The results of the sibling comparisons and
      meta-analysis corroborated these findings. CONCLUSIONS: Breast feeding
      has little or no effect on intelligence in children. While breast
      feeding has many advantages for the child and mother, enhancement of
      the child's intelligence is unlikely to be among them.

      (The effect referred to must be the number of IQ points -
      corresponding to an effect size of r<0.02 - MH)
      Greetings,
      Morten


      Morten Hesse
      Center for Alcohol and Drug Research
      KĂžbmagergade 26E, 2.
      1150 Copenhagen K
      Denmark
      Sent by Medscape Mail: Free Portable E-mail for Professionals on the Move
      http://www.medscape.com
    • L. Eugene Arnold
      MAIN OUTCOME MEASURE: IQ in children measured by Peabody individual achievement test. An achievement test does not measure IQ; it measures achievement. Gene
      Message 2 of 2 , Nov 1, 2006
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        "MAIN OUTCOME MEASURE: IQ in children measured by Peabody individual
        achievement test."
        An achievement test does not measure IQ; it measures achievement.
        Gene

        At 02:53 AM 11/1/2006, Morten Hesse wrote:
        >Concerning the difference in IQ between those breastfeeded and those
        >not: the effect size in this study is "over half a standard
        >deviation". Half a standard deviation corresponds to r=0.2425. That's
        >a big effect size. However, look at the summary below:
        >
        >BMJ. 2006 Oct 4; [Epub ahead of print]Click here to read Links
        > Effect of breast feeding on intelligence in children: prospective
        >study, sibling pairs analysis, and meta-analysis.
        >
        > * Der G,
        > * Batty GD,
        > * Deary IJ.
        >
        > MRC Social and Public Health Sciences Unit, Glasgow G12 8RZ.
        >
        > OBJECTIVE: To assess the importance of maternal intelligence, and
        >the effect of controlling for it and other important confounders, in
        <Snip>
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