"Media are increasingly pervasive in the lives of children
and adolescents # the average kid today spends nearly
45 hours per week with media, compared with 17 hours
with parents and 30 hours in school. However, until
now there has been very little comprehensive analysis of
the different research tracking the impact of media on
children's health."
Thus begins the executive summary of a metatstudy on the relationship between use of media and adolescent health. The research results were published December 2nd by the advocacy group Common Sense Media.
The study was undertaken by the National Institutes of Health, the Yale University School of Medicine, and the California Pacific Medical Center, and analyzed the "best [research] studies" undertaken since 1980 on this topic. One hundred seventy three "best studies" were identified.
Of specific interest was the impact of increased media usage on:
- obesity
- tobacco use
- drug use
- alcohol use
- low academic achievement
- sexual behavior
- Attention Deficit Hyperactivity Disorder (ADHD)
Although the researchers attempted to assess studies related to the usage of all media (the internet, magazines, movies, music, television, and video games), the researchers found that "most of the quality studies" investigated only the impact on adolescenthealth of movies, television and music.
Of the "best studies," 127 evaluated the relationship between the hours adolescents spent on media usage and health outcome. Seventy five percent of these 127 studies demonstrated an increase number of hours were associated with a "negative health outcome" and 20% showed no statistically significant relationship. Seven studies (6%) showed a positive relationship between media usage and some measure health outcome.
In the findings below, statistically significant means the results were unlikely to have occurred by chance.
Obesity: increased media usage was associated with increased incidence of obesity and increased weight gain over time. (Of 73 studies, 63 (86%) showed this association as statically significant.) A single longitudinal study begun with 5,493 three year old children found that children watching more than 8 hours of television "were significantly more likely to be obese at age seven."
Tobacco usage: increased media usage was associated with increased smoking, which was defined as ""children trying smoking, or beginning to smoke at an earlier age." (Of 24 studies, 21 (88%) showed this association as statically significant.)
Drug Usage: increased media usage was associated with increased drug usage, defined as "past or current use of specific recreational drugs including cocaine, marijuana, methamphetamines, and ecstasy." (Of 8 studies, 6 (75%) showed this association as statically significant.)
Alcohol Usage: increased media usage was associated with increased alcohol usage. (Of 10 studies, 8 (80%) showed this association as statically significant.)
Low academic achievement: increased media usage was shown to have a negative impact on academic achievement "measured through standardized test scores or school grades." (Of 31 studies, 20 (65%) showed this association as statically significant.)
Sexual behavior: increased media usage was associated with "a more rapid progression of initiation of sexual behavior.' (Of the 14 studies, 13 (93%) showed this association as statically significant.)
Attention Deficit Hyperactivity Disorder (ADHD): increased media usage was associated with "increased attention problems." (Of the 13 studies, 9 studies (69%) showed this association as statically significant.)
Too often, a single research study can fall victim to the "umbrella/rain" correlation fallacy. Technically known as "Post hoc ergo propter hoc" or Post hoc thinking, it can be reduced to "X happened, Y happened, therefore X caused Y to happen."
The fallacy lies in the assumed directionality. On days that it rains, we see many people with umbrellas. Did the increased number of people with umbrellas cause the rain to fall, or did the impending rain cause people to carry umbrellas? Does increased media usage lead to obesity, or are obese people more likely to watch more television?
By rigorous analysis of a large number of "best studies," a metastudy can avoid the correlation or Post Hoc fallacy.
Of the advantages of a metastudy, one is that it pulls together all printed research on a subject, in contrast to the single studies which often make the news.
In gathering the research studies for a quality metastudy, typically a panel independent of the reviewers ranks each of the collected studies as to quality of research methodology and quantity of subjects in each study. A quality metastudy can control for study variation and can utilize statistical methods such as regression techniques which may not be appropriate in small N studies.
Unless well defined and unless the input is independently evaluated and controlled, a metastudy can have the disadvantage of investigator bias or weak study bias.
A further disadvantage of metastudies of published research is that unpublished results are ignored, thus skewing the results (Studies which result in a null (no) relationship between two variables are seldom published. Thus if there are 1,000 studies of media and health outcomes which find no relationship, these are "lost" as the researchers collect the studies which show a relationship.)
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