I received a note from the author of the study, Luisa Livingstone, who provided more information and corrections- not the least of which is that she has not yet been awarded a PhD. This reflects her additional information.
So, yesterday, I described a meta-analytical study about ADHD. You recall that effecting a meta analysis means one examines data collected from various studies and attempts to see if there are correlative results among the studies. (See that word- correlative? Meta-analysis doesn’t really help to determine causation; it just lets one correlate large collections of data to see if there is a trend or factor that stands out.)
But, the findings that smaller amygdala size associated with ADHD is pretty pronounced- especially when the condition seems to reverse with age- and that correlates with a decrement in ADHD symptomatology. There still is a genetic component (70% of the difference that manifests as ADHD diagnosis) – which may be the cause why there is delayed brain development in young folk. But, that data needs more study.
In the meantime, other studies among twins – where one child manifests ADHD and the other doesn’t- proceed. A new one, with Luisa Livingstone as the primary author (with her co-researcher Dr. William Conventry [both folks were from University of New England, Australia], and EG Willcutt [U of Colorado], RK Olson [Linkoping, Sweden] and B Byre [Stavanger, Norway]) has just been published in the Journal of Abnormal Child Psychology (The title: Does the Environment Have an Enduring Effect on ADHD? A Longitudinal Study of Monozygotic Twin Differences in Children.)
This study examined 1024 identical twins (that’s 2048 folks) in the US, Scandinavia, and Australia. Since these are identical twins, the only difference between the twins should be environmental influences. The children were followed from preschool to third grade; but it was parental evaluation of the children that was the data employed in this study.
The children were evaluated using the Disruptive Behavior Rating Scale, a 18 question survey concerned with hyperactivity and inattentiveness (each involved 9 questions). (This is considered to be a valid test. Except my research expects the survey to be 45 questions!)
Most of the twins manifested similar sets of behaviors, but some had a consistent difference throughout the study (which means something happened before the first pre-school evaluation.)
However, a few had a difference for brief period- just one year. The researchers concluded (assumed?) this means something happened in their environment to affect the changed behaviors.
The problem? Since the difference only manifested for one year, there were no conclusions as to what changed the behavior. (LIvingstone asserts that these transient effects would not be present at the next test cycle, so there was no need to identify what those factors may be.) The researchers also believe that changing the environment could preclude the development of disruptive behaviors- however, they had not found what those factors may be.
Having thought that all researchers were at the PhD level, and that there were no defined results (the transient effects were too transient to examine and they had no identifying factor providing stable effects), I assumed that this publication was an example of publish or perish.
Instead, it was a vehicle for a budding researcher to develop skills writing about (her) research and to invite others to proceed further along this path of study.