In the previous posts in this series on ADHD and preterm birth or prematurity, I didn’t get into what really fascinates me about this connection: that subtle alterations in the structure of the brain are implicated in both prematurity and in attention-deficit/hyperactivity disorder.
Remember that significant brain development takes place in the third trimester of pregnancy. At 34 weeks gestation, for example, the developing brain weighs only 65% of what it will weigh at a full-term 40 weeks. Incredible growth and connectivity takes place during the final weeks of pregnancy to ready a mind for its all-important function out of the womb, and early birth changes the environment in which that development takes place.
Beyond noting the amount of brain growth that takes place outside the womb, though, many studies have looked at the specific regions of the brain that are affected by preterm birth.
White Matter and the Salience Network in Prematurity and ADHD
For example, in a 2014 article on “Preterm birth and structural brain alterations in early adulthood,” in the journal of “NeuroImage. Clinical”, examined structural changes in grey matter and white matter in former preemies observed as young adults. Grey matter is the part of the brain responsible for content; white matter is instead about the connections across, between, and within different parts of the brain. The study’s authors noted that the earlier a baby is born, the more of a difference they saw in the structure of both grey and white matter even into young adulthood. In other words, the earlier the preemie, the greater the risk, seems to be the refrain.
In an even more recent study from early 2017, “Association of Preterm Birth With ADHD-Like Impairments,” researchers compared preterm adolescents to term-born adolescents both with and without diagnoses of ADHD. The youths took a test measuring various aspects of attention, including preparing to respond, executive control of response and inhibiting or stopping a response. I’ve taken a similar test to the one described in the article, and noted my own surprising difficulty in following through with the seemingly basic instructions (“hit a spacebar when all of these things happen, except when this other thing happens, don’t hit it.” I hit it nearly every time… ) The researchers’ results surprised me:
“Although the response preparation and response inhibition impairments found in preterm-born adolescents overlap with those found in term-born adolescents with ADHD, the preterm group also shows unique impairments, suggesting more wide-ranging impairments in the preterm group compared to the ADHD group.”
In other words, although preterm adolescents showed similar symptoms to full-term youth with ADHD, the preterm group also showed other impairments not present in the full-term group. Prematurity, once again, emerges as something with its own set of symptoms and challenges, not easily or fully described by common diagnostic labels.
Researchers in this study support this conclusion, suggesting that:
“Preterm birth may result in trauma to the brain networks associated with ADHD, as well as networks associated with additional impairments.”
Finally, a 2015 study reported in The Guardian noted that certain regions of a preemie baby’s brain seems to be differently affected by the facts of prematurity. According to this study, the salience network (a collection of regions in the brain that determine which stimuli to pay attention to), showed reduced connectivity in former preemies. This region, interestingly, is the same region found to be differently affected in both ADHD and autism — and in premature babies as well.
ADHD and Prematurity: Take-Away Points
What do I take away from these observations?
First, I’m reminded that diagnoses aren’t set in stone; they’re our way of trying to categorize certain types of behaviors. Since these behaviors exist on a continuum from clinically significant, to subclinical, to unimpaired, the picture muddies even more.
Second, these subtle differences seem to be rooted in differences in brain structure, sometimes subtle, sometimes significant, that overlap with, but aren’t equivalent to, certain conditions.
Third, as with any diagnosis, the presence of neurological differences can be as much a relieving explanation as it is a challenge to work with, not against, one’s innate tendencies — but in a productive way. Make them work for you, rather than struggle against them. That’s the secret we’re all striving for, after all.