A new study of behavior problems in children prenatally exposed to methamphetamine has prompted predictably alarming headlines that recall the panic about "crack babies," who supposedly were handicapped for life by their mothers' drug use. Those concerns turned out to be wildly overblown, and for years scientists who regret that episode have been warning their colleagues not to make the same mistake with "meth babies." But such admonitions may be no match for researchers' natural tendency to exaggerate the importance of their findings, combined with journalists' constant thirst for a good scare story.
In this case, researchers led by Brown University psychologist Linda LaGasse compared the Child Behavior Checklist (CBCL) scores of 166 children whose mothers had consumed meth during pregnancy to those of 164 children whose mothers had not. The two groups, drawn from four cities (Los Angeles, Honolulu, Des Moines, and Tulsa), were matched for "race, birth weight, public health insurance, and education," and the kids were assessed at ages 3 and 5 based on an oral questionnaire answered by their caregivers. "This first report of behavior problems in patients as young as 3 years associated with MA [methamphetamine] exposure identifies an important public health problem," LaGasse and her colleagues write in the April issue of Pediatrics. "These effects on behavior problems are quite robust and may have substantial public health implications because problems as noted on the CBCL tend to persist over time and predict later psychopathology and criminal behavior that place tremendous burdens on society."
Sounds serious. If you look at the overall CBCL scores, however, you will see that the exposed and nonexposed kids were virtually indistinguishable. At age 3, the "total problems" score was 52.2 for the exposed children and 51.1 for the comparison group; at 5, the scores were 52.9 and 50.2, respectively. In neither case was the difference statistically significant. The two groups' "internalizing" scores (which include four subscales) also were essentially the same. "There were no effects of MA on the internalizing or total behavior problems scales," LaGasse et al. report.
Instead of concluding that the two groups were basically the same, the researchers focus on a few subscales where there were statistically significant differences. "MA exposure was associated with increased emotional reactivity and anxious/depressed problems at both ages and externalizing and attention-deficit/hyperactivity disorder problems by age 5 years," they write. The differences range from slightly less than a point to slightly more than a point. "Because CBCL findings are based on caregiver report," the authors concede, "there could be reporting bias." In other words, the mothers or other caregivers who answered the questionnaires may have been more inclined to perceive and report problems precisely because they worried about the potential damage caused by meth exposure. There was a similar weakness in much of the research on children exposed to cocaine in the womb.
Assuming the score gaps reflect real differences, how do we know they are caused by prenatal exposure to methamphetamine? To their credit, LaGasse et al. take into account a bunch of other variables: "prenatal exposure to alcohol, tobacco, and marijuana; birth weight; gender; SES [socioeconomic status]; maternal age; single (no partner); caregiver change; domestic violence; postnatal use of MA; tobacco, alcohol, and marijuana exposure; caregiver psychological symptoms; the quality of the home; child abuse; and study site." But they concede that "our measure of child abuse through caregiver report of Child Protective Services likely underestimates abuse." Likewise, their measure of "caregiver psychological symptoms" (which were associated with children's behavior problems) may not have captured all of the relevant differences between women who smoke meth when they're pregnant and women who don't.
In short, it is not clear from these data that "meth babies" (as several headlines called them) are different from other children in practically significant ways, that they represent "an important public health problem," that they they will "place tremendous burdens on society," or even that meth itself is the cause of any differences that actually exist. Given the cautionary example of "crack babies"—who were stigmatized as dramatically and permanently damaged, while their mothers were singled out for special condemnation and punishment—researchers and the journalists who trumpet their findings should try to be a little more careful this time around.
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