(RxWiki News) Sometimes factors in our environment increase our risk of a particular condition without actually causing that condition. Still, knowing those factors can be helpful, for example, when it comes to ADHD.
The researchers found that several different factors related to a child's time in the womb might be linked to ADHD.
For example, a mother's smoking during pregnancy doubled her child's odds of being diagnosed with ADHD later.
"Ask your pediatrician about your child's ADHD treatment."
This study, led by Desiree Silva, MPH, of the Telethon Institute for Child Health Research at University of Western Australia, looked at what environmental factors might be related to ADHD rates in boys and girls.
Environmental risk factors are characteristics of a children's environment or experience that may influence their risk of a particular condition.
The researchers examined the medical and personal histories of all 12,991 individuals born in Western Australia who were under 25 years old, had been diagnosed with ADHD and had been prescribed ADHD medications.
Information about these individuals' mothers, time in the womb and births were compared to the same information for 30,071 other individuals of the same ages who did not have ADHD.
The researchers found a number of factors that were linked to a higher likelihood of being diagnosed with ADHD.
However, it's not clear how each of these factors might actually be related to ADHD.
The study could not determine that any of these factors might have caused ADHD — just that they were linked to a higher risk for the condition.
For example, single mothers and younger mothers were more likely to have children diagnosed with ADHD than married mothers or mothers older than age 24, though that doesn't mean being young or unmarried causes ADHD.
Children also had twice the odds of being diagnosed with ADHD if their mother smoked during pregnancy than if she didn't.
Similarly, women who nearly had their baby preterm (before 37 weeks of pregnancy) due to complications had twice the odds that their child would be diagnosed with ADHD.
The odds of having ADHD were slightly increased (about 25 percent for boys and 33 percent for girls) if the child's mother's labor had been induced instead of occurring naturally.
A similar level of increased odds of ADHD existed for children whose mothers had experienced pre-eclampsia or had a urinary tract infection while pregnant.
Pre-eclampsia is a pregnancy complication in which the mother has high blood pressure and protein in her urine.
Girls had half the odds of being diagnosed with ADHD if their mothers had received the medication oxytocin to help her pregnancy labor. This finding did not exist for boys.
Several factors were also found not to have any link at all to ADHD.
Children born with a low birth weight, born after 40 weeks of pregnancy or born underweight for the pregnancy week they were born were no more likely than children without these characteristics to have ADHD.
Also, babies who showed "fetal distress" during delivery or who had a low Apgar score were no more likely than other babies to have ADHD.
An Apgar score is a score from 0 to 10 that is given to babies at birth as a quick indication of their apparent health. A score of 10 is the healthiest.
"Importantly, we found that risk associations were generally similar for boys and girls with ADHD," the authors of this study wrote. "The risk of ADHD remained elevated in children exposed to maternal smoking, preeclampsia, maternal UTIs, induced labor, and early term deliveries, irrespective of gender."
However, a couple risk factors seemed specific to a baby's sex.
"For boys, threatened preterm labor was an elevated risk, and for girls the rare condition of cord prolapse nearly tripled the risk of ADHD," they wrote. Cord prolapse means the umbilical cord comes out the birth canal before the baby does.
This study was published December 2 in the journal Pediatrics. The research was funded by the National Health and Medical Research Council Program. The authors declared no potential conflicts of interest.