That Teen-Sex and TV Study

You will have seen this in the news, the study showing that teen pregnancy is correlated with watching TV shows with a lot of sex in them. Like, here's this morning's Washington Post:

Teenagers who watch a lot of television featuring flirting, necking, discussion of sex and sex scenes are much more likely than their peers to get pregnant or get a partner pregnant, according to the first study to directly link steamy programming to teen pregnancy.

The study, which tracked more than 700 12-to-17-year-olds for three years, found that those who viewed the most sexual content on TV were about twice as likely to be involved in a pregnancy as those who saw the least.

"Watching this kind of sexual content on television is a powerful factor in increasing the likelihood of a teen pregnancy," said lead researcher Anita Chandra. "We found a strong association." The study is being published today in Pediatrics, the journal of the American Academy of Pediatrics.

There is rising concern about teen pregnancy rates, which after decades of decline may have started inching up again, fueling an intense debate about what factors are to blame. Although TV viewing is unlikely to entirely explain the possible uptick in teen pregnancies, Chandra and others said, the study provides the first direct evidence that it could be playing a significant role. Study First to Link TV Sex To Real Teen Pregnancies

We were having a conversation at our house recently where my kids, who are now 18 and 19, were saying "everybody" is pregnant. They started naming people, and wow, it's not literally everybody of course, but they do know a lot of young women who are pregnant. My son thought this was due to the movie Juno, which came out last year and featured a pregnant girl as the protagonist. You know me, I never see any of the movies, so I couldn't tell you, and I doubt that one movie is responsible for a significant increase in teen pregnancy, but the phenomenon is something you can observe firsthand on the streets of Montgomery County.

If you ever took a statistics course, you hopefully learned that correlation does not imply causation. It looks like you have to pay to read the article itself, or go to a library that carries the journal Pediatrics, but you can read the summary at the Rand site HERE. Here's the meat and potatoes of the summary:

Methods
Data from a national longitudinal survey of teens (12-17 years of age, monitored to 15-20 years of age) were used to assess whether exposure to televised sexual content predicted subsequent pregnancy for girls or responsibility for pregnancy for boys. Multivariate logistic regression models controlled for other known correlates of exposure to sexual content and pregnancy. We measured experience of a teen pregnancy during a 3-year period.

Results
Exposure to sexual content on television predicted teen pregnancy, with adjustment for all covariates. Teens who were exposed to high levels of television sexual content (90th percentile) were twice as likely to experience a pregnancy in the subsequent 3 years, compared with those with lower levels of exposure (10th percentile).

When they say that television exposure "predicated" pregnancy, they are saying a certain thing about how the regression equations were set up. For instance, let's say you had a study that found that waist size (WS) "predicted" weight in pounds (WP), with the formula WP = a + b*WS. I know, I hate to use a bunch of math here, but we're saying that if you know waist size (WS), you can multiply it by something and add something to the product and you can estimate or "predict" weight in pounds (WP). But you could turn it around, too, you could say that weight in pounds (WP) predicts waist size, you could use the formula WS = a + b*WP -- saying, if you know somebody's waist size you can estimate their weight. "Predicting" just means that if you know one fact you can estimate another one, and often that goes both ways. It does not mean that one thing causes the other.

In other words, this study doesn't say that watching sexy television causes teens to end up pregnant. It could just as easily say that pregnancy-prone kids have a tendency to watch shows with sex in them.

I saw this on the front pages of some papers this morning, so you can bet it's going into somebody's arsenal of arguments about why America needs to be even more puritan than it is. But look at the Netherlands, where everything goes, where sex education is thorough and parents expect their children to have sex and thus prepare them for it -- and where television is relatively wide-open sexually, compared to here. Where the US has a teen pregnancy rate of 53 per 1,000 women aged 15-19, the Netherlands' rate is 5 per 1,000.

So let's say I would take this study with a grain of salt. Teens who are fascinated by sex are more likely to get pregnant -- that's not so surprising. Or it could be that teens who watch television all day are too lazy to use contraception. This is a hard kind of study to draw any conclusions from.