Meer op junkonderzoek

Hans van Maanem scrivt op deze manuscript hier van Michael Foster. Hans scrivt:

I [Hans] wrote about the paper when it came out — not as thorough, I am afraid, but enough to warn readers against this kind of science. Maybe your colleagues are heartened by the fact that not everybody took it at face value! Could you please forward them my column from May 2004 in De Volkskrant (and maybe translate it…)?

ADHDTV

Wat je ook nóóit moet doen: je peuter voor de televisie zetten. Daar krijgt-ie ADHD van. ‘Beperking van de blootstelling van jonge kinderen aan televisie zou het risico op ADHD op latere leeftijd kunnen verminderen,’ schrijven Dimitri Christakis en collega’s uit Seattle in het jongste nummer van het vakblad Pediatrics. Het artikel kreeg buitensporig veel aandacht in de Amerikaanse media.

Tussen de 4 en 12 procent van de kinderen daar krijgt het etiket ‘ADHD’ opgeplakt, en Christakis vroeg zich af of ‘zeer vroege blootstelling aan televisie in de kritische periode dat de ontwikkeling van de hersenverbindingen ontwikkelen, verband zou houden met latere aandachtsproblematiek.’

Dus haalde hij de gegevens tevoorschijn van de National Longitudinal Survey of Youth uit 1979, en bekeek de lotgevallen van 1278 kinderen van bijna twee jaar (de ‘eenjarigen’) en 1345 kinderen van bijna vier (de ‘driejarigen’). De meeste eenjarigen, bijna de helft, keken in het geheel geen televisie, maar er waren ook moeders die zeiden dat hun kinderen zestien uur of meer televisie keken per dag. Van de kinderen van bijna vier keek nog maar 10 procent nooit televisie, de helft keek tussen de een en drie uur per dag.

Omdat twintig jaar geleden nog niemand van ADHD gehoord had, moest Christakis meteen al wat schipperen, en een maat bedenken voor de aandachtsproblemen van de kinderen. Een echt verband tussen ADHD en televisiekijken kon hij dus niet vaststellen, zo erkent hij zelf al.
Maar toch, voor elk uur dat de peuters (zowel de een- als de driejarigen) meer televisie keken, steeg de kans op aandachtsstoornissen met 9 procent. Dat klinkt indrukwekkend, maar het is volstrekt niet te interpreteren, omdat de verhoudingen zo scheef lagen. Waren die paar kinderen die zestien uur of meer keken niet zo gestoord dat ze de kinderen meetrokken die twee of drie uur voor de buis zaten? Het is zeer de vraag of de rekenmethode die Christakis heeft gebruikt, hier ook maar iets zinnigs oplevert.

En dan nog ligt de tegenwerping voor de hand, dat er van enig oorzakelijk verband geen sprake hoeft te zijn. De auteurs erkennen dat bezwaar wel, maar stappen er kwiek overheen. Het zou kunnen dat kinderen die buitengewoon lastig zijn, in arren moede maar voor de televisie worden gezet. Of dat moeders die hun kinderen zestien uur televisie laten kijken, ook voor het overige een bijzonder bewind voeren. Zelfs om een niet-oorzakelijk verband vast te stellen, is deze studie nogal zwak.

Wat de onderzoekers wegmoffelen, is dat bijna elke andere onderzochte factor beter de problemen voorspelt dan televisie. Een uur kijken houdt, zoals gezegd, verband met 9 procent meer aandachtsstoornissen, maar geringe emotionele steun met 18 procent, evenals een gebrek aan cognitieve stimulatie. De allerbelangrijkste factor, voorzover het uit de tabellen is op te maken, lijkt echter het zelfbeeld van de moeder. Als die een lage dunk van zichzelf heeft, is de kans op aandachtsstoornissen verhoogd met meer dan 30 procent. Als televisie kijken werkelijk een rol speelt, is het dus eerder een zeer geringe rol.

Niettemin laten de auteurs alle bescheidenheid varen als zij hun conclusies trekken. ‘Wij hebben aandachtsproblemen toegevoegd aan de kwalijke effecten van buitensporig televisie kijken, naast gewelddadig gedrag en overgewicht.’

Christakis heeft twee kinderen, van drie en zes jaar, en gelooft in de waarde van een leven zonder televisie. ‘Toen mijn zoon net drie maanden was en ik met hem in een winkel was, viel het mij op dat hij zijn ogen niet van het scherm kon afhouden,’ zei hij in een interview naar aanleiding van zijn publicatie.

3 thoughts on “Meer op junkonderzoek

  1. Here is my version of the translation – hope it's helpful!

    ADHDTV

    Another thing you should never do: put your toddler in front of the television. He’ll get ADHD from that. “Limiting young children’s exposure to television minimizing the risk of ADHD in later ages,” write Dimitri Christakis and colleagues in Seattle in the the journal Pediatrics. This article received a lot of attention in the American news.

    Between 4 and 12 percent of children in the U.S. gets the label “ADHD” stuck on them, and Christakis wondered if that “very early exposure to television, in the critical time when they are developing their brain connections, could be linked to later attention issues.”

    He took evidence from the National Longitudinal Survey of Youth from 1979 and looked at the outcomes of 1,278 children of almost two years of age (the “one-year-olds”) and 1,345 children of almost four years of age (the “three-year-olds”). Most one-year-olds, almost half, did not watch television at all, but there were also mothers who said that their children watched sixteen hours or more of television per day. Of the children who were almost four, only 10 percent never watched television, and half watched between one and three hours a day.

    Because no one had heard of ADHD twenty years ago, Christakis had to create a measure of attention problems of the children in the survey. A connection between ADHD and watching television could not be truly measured; he freely admits that. But still, for every increased hour that the toddlers (the one- and three-year-olds) watched television, the chance of attention issues rose by 9 percent. That sounds impressive, but it is not really interpretable because the range of responses was so large. Were those few children who watched sixteen hours of television or more in a day not so messed up that they pulled along those children who watched two or three hours a day? The question is, do the methods that Christakis used actually result in something sensible?

    And then there is also the counter-argument: that there does not have to be a causal connection. The authors bring up this argument but evade an explanation. It could be that children who are incredibly difficult are just placed in front the television for lack of a better idea. Or that mothers who allow their children to watch sixteen or more hours of television might lead very interesting and different lives. Even to show a non-causal connection this study is fairly weak.

    What the researchers do not discuss is that almost every other factor predicts problems more than watching television does. One hour of watching television, as mentioned previously, is linked to 9 percent more attention issues, but low levels of emotional support are linked to 18 percent, as is a lack of cognitive stimulation. The most important factor, at least as far as can be seen in the tables of data, is the self-image of the mother. If she has a low opinion of herself, the chance of the child having attention issues goes up more than 30 percent. If watching television truly plays a role, it is then a very small role.

    Even so, the authors let their modesty go as they draw their conclusions. “We have added attention problems to the effects of watching too much television, next to aggressive behavior and being overweight.”

    Christakis has two children, three and six years of age, and believes in the worth of a life without televistion. “When my son was three months out and I was with him in a store, I noticed that he could not take his eyes off of the television screen,” he told me in an interview before his publication.

  2. What you should *never* do: put your toddler in front of the television. It will give him ADHD. "Limiting exposure of young children to television may reduce the risk of having ADHD later in life", so write Dimitri Christakis and colleague's from Seattle in the latest issue of the journal Pediatrics. The article received excessive media attention in the United States where between 4 and 12 percent of children are labeled with ADHD.

    Christiakes wondered whether "very early exposure to television during the critical period when cerebral connections develop, could be related to later attention deficits".

    He therefore took out the data from the NLSY from 1979, and looked at the fate of 1278 children of almost two years (the 1-year-olds) and 1345 children of nearly four (the 3-year-olds). Most 1-year-olds, nearly half of them, did not watch television at all, but there were also mothers who stated that their children watched sixteen hours or more television per day. Of the 3-year-olds only 10 percent never watched television. Half watched between one and three hours a day.

    Because 20 years ago nobody heard of ADHD, Christakis had to make some compromises and construct a measure for the attention deficits of the children. He admits that he could therefore not establish a real relation between ADHD and television. But still, for every hour that the toddlers (both 1 and 3-year-olds) watched television the likelihood of attention deficits increased by 9 percent. This sounds impressive, but it is absolutely not to interpretable because the relationships were so skewed. Were those few children who watched sixteen hours or more not so disturbed that they pulled the children who spend two or three hours in front of the tube? It is very doubtful whether the method that Christakis used will give something sensible.

    And then, there is the obvious critique that there is no causal connection at all. The authors acknowledge this, but are quick to ignore it. It could be that children who are extremely difficult, are put in front of the television. Or that mothers whose children watch sixteen hours of television, are also special in other respects. Even in establishing a a non-causal relationship this study is rather weak.

    What the researchers shuffle under the carpet is that almost every other factor examined predicts the problems better than television. One hour television, as mentioned, is associate with 9 percent more attention deficits, but limited emotional support with 18 percent, just like lack of cognitive stimulation. The most important factor, as far as can be seen from the tables, is the self-image of the mother. If she has a low opinion of herself the probability of attention deficits is increased by more than 30 percent. If watching television really plays a role, it is seem to be a very minor one.

    Nonetheless, the authors let all modesty sail as they draw their conclusions. "We have added attention deficits to the harmful effects of excessive television watching, in addition to violent behavior and overweight."

    Christakis has two children, three and six years, and believes in the value of a life without television. "When my son was only three months and I was with him in a store, I noticed that he could not keep his eyes from the screen", he said in an interview following the publication.

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