Predicting Impulsivity in Young Adults
Post by Anastasia Sares
What's the science?
A failure to control impulsivity is common to many psychiatric conditions, which often emerge in young adulthood as the frontal lobe completes its development. Finding the specific neural mechanisms behind impulsivity could help us diagnose and treat this aspect of mental health. This week in Molecular Psychiatry, Steele and colleagues looked at the brain areas involved in impulsivity, using a large and diverse group of young adults with different mental health profiles.
How did they do it?
The authors collected functional MRI scans to measure the brain activity of a number of young adults (18-25 years old) who were seeking treatment for a variety of psychiatric conditions (as well as young adults who had no diagnosis and no treatment). Psychiatric conditions were evaluated in a structured interview, and some of those with a diagnosis also came back for a follow-up session.
During the MRI scan, participants looked at a series of faces with different emotions at varying intensities, as well as some gray ovals that had no facial information. This way, the authors could see which brain areas tracked emotional intensity.
The participants also completed an impulsivity questionnaire with 5 subcategories:
Negative urgency (urgency to act on negative emotions)
Positive urgency (urgency to act on positive emotions)
Lack of premeditation (not thinking ahead)
Lack of perseverance (giving up on things)
Sensation-seeking
Based on previous literature, the authors thought that impulsivity would predict:
Higher activity in the amygdala (a structure known for its response to fear)
Altered activity in the prefrontal cortex (known for inhibition and emotional control)
Lower connectivity between the amygdala and the prefrontal cortex (less regulation of emotional responses)
What did they find?
The authors found that the amygdala significantly responded to the emotional faces. As predicted, the strength of the left amygdala’s response to fearful faces was correlated with a person’s impulsivity, specifically negative urgency and lack of perseverance. The connectivity between the amygdala and prefrontal cortex was also related to impulsivity, with less connectivity in more impulsive people. This confirmed the authors’ second and third predictions. Finally, for the 30 participants who came for a follow-up evaluation 6 months later, the amygdala’s response to sad faces in the first session predicted overall impulsivity at follow-up.
What's the impact?
This work is a step forward in our understanding of the brain areas involved in impulsivity and may provide targets for diagnosis and treatment of psychiatric conditions. However, the authors are quick to point out that the study requires replication. Testing so many people with different psychiatric conditions is good for the generalizability of the results to the general population, but it also means that other factors related to these disorders could confound the results. Although this study attempts to remove the influence of other factors, the best confirmation is to repeat the experiment in an independent sample.
Steele et al. A specific neural substrate predicting current and future impulsivity in young adults. Molecular Psychiatry (2021). Access the original scientific publication here.