A study of 10 million siblings in the United States found differences between first- and second-born health problems. ADHD, autism, Tourette syndrome and obsessive-compulsive disorder were diagnosed more often among first-borns, while migraines, shingles, gastritis and substance use disorders were more common in second-borns, reports Fox News.
Researchers from the University of Chicago and Columbia University analyzed, for two decades, the medical data of the siblings included in the study. They looked at 569 disease categories and found that for 150 of them, there were significant differences by birth order.
What problems occur more often in the first child?
For first-borns, researchers have seen a higher likelihood of being diagnosed with certain disorders including autism, ADHD, Tourette’s syndrome and obsessive-compulsive disorder. Allergic conditions, including food allergies, were also observed more frequently in this category.
Dr. Marc Siegel, quoted by Fox News, says that the study raises many questions, and the causes of the observed differences between the siblings are not yet clear. In his opinion, one of the explanations could be the attention that parents pay differently to their children.
In the case of ADHD, the doctor believes that the first-born may be exposed to more stimuli, precisely because the parents tend to be more attentive to him. But it is a hypothesis formulated by Siegel, not a conclusion of the study.
The doctor proposes a possible explanation for the allergies found more often in first-borns. He believes that it could matter how the child’s immune system reacts to the first contacts with the environment.
What they discovered in the case of the second child
In contrast, migraines, shingles, gastritis and substance use problems were more common in the second child.
The study does not determine why these differences occur. Among the possible explanations are the changes that the mother’s body goes through after the first pregnancy, the environment in which the children grow up, but also the way in which the parents’ behavior changes from the first to the second child.
Birth order does not mean that a child will develop a particular disease
However, researchers say that birth order is not necessarily the reason why these conditions occur.
The results may have other explanations. For example, parents can be more attentive to certain symptoms in the case of a child and can take him to the doctor more quickly. Moreover, the age of the parents, the age difference between the siblings or the changes that occur in the family with the arrival of the second child can also matter.
Therefore, the research cannot say that the first or second born will have certain health problems. Rather, the differences found in the 10 million siblings provide new clues to understanding why certain conditions occur more often in some children than in others.
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