An experimental study of individuals with ADHD revealed that those with increased gyrification in frontal cortical regions of the brain generally responded better to treatment. The treatment was either group psychotherapy or methylphenidate in combination with clinical management of symptoms.
However, neither group psychotherapy nor methylphenidate was more effective overall than the control conditions. The paper was published in Translational Psychiatry.
Cortical gyrification is the process by which the brain’s cerebral cortex folds into ridges (gyri) and grooves (sulci) during development, increasing its surface area without greatly expanding skull size.
These folds allow a much larger number of neurons and connections to fit within the limited space of the cranium. Gyrification begins prenatally and continues into early childhood as different brain regions mature at different rates.
Higher degrees of gyrification are generally associated with increased cognitive capacity because more cortical surface supports more complex neural processing.
However, the pattern of folds, not just their number, is important for efficient connectivity between brain regions. Abnormal gyrification—either too little or too much—has been linked to neurodevelopmental conditions such as autism, schizophrenia, and certain genetic disorders.
Study author Jonathan Laatsch and his colleagues wanted to explore whether the effects of treatment for attention-deficit/hyperactivity disorder (ADHD) symptoms depend on the degree of cortical gyrification in adults suffering from this disorder. Their general expectation was that individuals with higher levels of cortical gyrification would show a stronger response to treatments (i.e., stronger reductions in symptoms).
They conducted an experimental study (randomized controlled trial). While the parent study included 419 adults suffering from ADHD, the final sample for this specific neuroimaging analysis consisted of 121 participants. Their ages ranged between 19 and 58 years, with the average being 35 years. The number of males and females was roughly equal.
Study participants were randomly divided into 4 treatment groups for different 12-week treatments. The first group was to undergo group psychotherapy while taking methylphenidate. The second group was also undergoing group psychotherapy, but received placebo medications (capsules looking exactly like methylphenidate capsules, but with no active ingredients). The third group underwent clinical management of symptoms and received methylphenidate, while the 4th group received clinical management of symptoms and placebo.
Group psychotherapy consisted of weekly sessions for 12 weeks and then monthly for 10 additional sessions. Clinical management was an active control condition that simulated routine psychiatric care consisting of nondirective supportive counseling on the basis of individual sessions lasting 15–20 minutes.
Methylphenidate is a stimulant medication used to improve attention, focus, and impulse control. It is commonly prescribed for ADHD. For participants receiving this medication, the dose was gradually increased over 6 weeks until 60 mg/day was reached. Participants did not know whether they were receiving methylphenidate or placebo, but were aware whether they were receiving group psychotherapy or clinical management.
Participants underwent magnetic resonance imaging (MRI) of their brains, allowing study authors to calculate the level of cortical gyrification. ADHD symptoms were rated by the researchers using the Conners’ Adult ADHD Rating Scale.
Results showed that clinical management was better than group psychotherapy in reducing the total number of ADHD symptoms. However, in participants undergoing group psychotherapy, lower gyrification in the right precuneus and the paracentral gyrus was associated with lower levels of inattention (one of the symptoms of ADHD) after treatment. Conversely, across the whole sample, higher gyrification was associated with stronger overall symptom reduction.
Similarly, among participants receiving methylphenidate, individuals with lower gyrification in the left rostral middle frontal gyrus tended to have lower levels of hyperactivity. However, methylphenidate was not more effective than placebo in reducing ADHD symptoms.
“Results revealed significant positive region-specific associations between cortical gyrification and treatment response across three symptom dimensions, with significant associations localized predominantly in frontal regions of the left hemisphere. Our findings emphasize that increased cortical gyrification in frontal cortical regions signifies enhanced treatment efficacy following a 12-week intervention,” the study authors concluded.
The study contributes to the scientific knowledge about methods for treating ADHD. However, neither of the main treatments used in this study (group psychotherapy and methylphenidate medication) was more effective than the corresponding control conditions.
Additionally, participants were aware whether they were undergoing group psychotherapy or the clinical management condition, leaving room for the Hawthorne effect to have affected the results. The Hawthorne effect happens when study participants change their behavior because they know they are being observed and that they are participating in a study.
The paper, “Cortical gyrification predicts initial treatment response in adults with ADHD,” was authored by Jonathan Laatsch, Frederike Stein, Simon Maier, Swantje Matthies, Esther Sobanski, Barbara Alm, Ludger Tebartz van Elst, Axel Krug, and Alexandra Philipsen.
