A pair of recently concluded long-term studies may shine some light on the causes of ADHD as well as other mental illnesses including bipolar disorder, autism and psychosis.
In the first, published online by JAMA Pediatrics, researchers at UCLA linked the use by pregnant women of over-the-counter acetaminophen—the pain reliever in Tylenol—with a heightened risk of both attention deficit/hyperactivity disorder and hyperkinetic disorder, an especially severe form of ADHD. The researchers reviewed the health histories of some 64,000 children and mothers in the Danish National Birth Cohort between the years 1996 to 2002—histories that included phone interviews during pregnancy, six months after childbirth, and when children turned seven. Birth Cohort moms had taken a standard behavioral screening questionnaire while pregnant; researchers also checked with the national health registries for diagnoses of hyperkinetic disorder and use of ADHD meds.
More than half the mothers in the study had used acetaminophen while pregnant. That’s not unusual; for years doctors around the world have considered it safe when taken by moms-to-be, and it’s the most commonly used medication for pregnant women suffering fevers and pain. But the study showed the children of those moms had a 13 to 37 percent increased risk of being diagnosed with hyperkinetic disorder, displaying ADHD-associated behaviors at age seven, or taking ADHD meds. The risk increased with the length of time of exposure; it was 50 percent higher when a mother took acetaminophen for longer than 20 weeks in the course of her pregnancy. For now, the association remains correlative; more study is needed to show cause. But UCLA professor Beate Ritz, one of the study’s senior authors, notes that animal studies show acetaminophen disrupts hormones, and that such disruption could affect brain development.
In the study of older dads, published in JAMA Psychiatry, researchers combed medical and public records of 2.6 million people born in Sweden between 1973 and 2001 (hooray for Scandinavian recordkeeping!), screening for paternal age at a child’s birth and the mental health histories of the kids, as well as of their siblings. Previous studies have shown risks to children born to older dads, but this study indicates those risks may be greater than once thought. When researchers compared kids born to dads ages 20 to 24 with those born to men 45 and older, the latter offspring were twice as likely to become psychotic, three times more likely to be diagnosed with autism, 13 times as likely to have ADD, and 25 times more likely to be diagnosed with bipolar disorder.
Again, the associations are correlative; science hasn’t shown how or why the increase occurs, though researchers suspect that the continuous production of sperm cells increases the number of random gene mutations, and that such mutations could affect brain development. They also point out that for autism and psychosis, even the increased levels leave a child’s risk quite low. The much higher risk factors for ADD and bipolar disorders are more baffling. Even so, University of North Carolina genetics professor Patrick F. Sullivan, who didn’t join in the study, told the New York Times, “[T]he last thing people should do is read this and say, ‘Oh no, I had a kid at 43, the kid’s doomed.’ The vast majority of kids born to older dads will be just fine.”
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