How Do Genetic Factors Influence Attention and Impulsivity in ADHD?

What you need to know

• Researchers examined how genetic risk for ADHD relates to attention and impulsivity problems in people diagnosed with the disorder
• They found that higher genetic risk for ADHD was associated with more variable reaction times, indicating attention regulation difficulties
• However, genetic risk for ADHD was not significantly related to commission errors, a measure of impulsivity
• This suggests genetic factors influencing ADHD may have a stronger impact on attention processes than impulse control

Understanding ADHD and genetics

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental condition characterized by persistent inattention and/or hyperactivity-impulsivity that interferes with functioning. While we know ADHD runs in families and has a strong genetic component, researchers are still working to understand exactly how genetic factors influence the cognitive and behavioral symptoms of the disorder.

Recent advances in genetics have allowed scientists to calculate “polygenic risk scores” that estimate an individual’s genetic liability for ADHD based on findings from large genome-wide association studies. This study used these polygenic risk scores to examine how genetic risk for ADHD relates to specific cognitive impairments often seen in the disorder.

Measuring attention and impulsivity

The researchers focused on two key cognitive processes that are frequently impaired in ADHD:

1. Attention regulation - measured by reaction time variability (RTV), which captures how consistently a person responds across multiple trials of a task. More variable reaction times indicate difficulties sustaining attention.

2. Response inhibition - measured by commission errors, which are incorrect responses to non-target stimuli on tasks requiring the person to withhold responding. More commission errors indicate greater impulsivity.

These measures were obtained from various computerized tasks across multiple research sites, allowing the researchers to combine data from 845 people diagnosed with ADHD.

Genetic risk linked to attention problems

When analyzing the combined data across all research sites, the study found a significant association between higher polygenic risk scores for ADHD and greater reaction time variability. This suggests that common genetic variants that increase risk for ADHD diagnosis also contribute to difficulties with attention regulation in people who have the disorder.

The connection between genetic risk and reaction time variability was fairly consistent across different sites and tasks, even though the specific cognitive tests used varied. This speaks to reaction time variability as a robust marker of attention problems in ADHD that appears to have shared genetic influences with the broader diagnosis.

No clear genetic link to impulsivity

Interestingly, the researchers did not find a significant relationship between polygenic risk scores for ADHD and commission errors on the cognitive tasks. This suggests that the common genetic variants captured by current genome-wide association studies of ADHD may not have as strong of an influence on impulsivity and response inhibition abilities.

This finding aligns with some previous research indicating that attention regulation and response inhibition may have partially distinct genetic and neurobiological underpinnings in ADHD. The genetic factors that increase risk for receiving an ADHD diagnosis may more strongly impact attentional processes compared to impulse control.

Conclusions

• Common genetic variants associated with ADHD diagnosis also influence attention regulation difficulties in people with the disorder
• The same genetic factors do not appear to be as strongly linked to impulsivity, at least as measured by commission errors on cognitive tasks
• This suggests some separation between the genetic influences on attention versus impulse control in ADHD
• More research is needed to further clarify the genetic and neurobiological pathways involved in different aspects of ADHD

While this study provides important insights into the genetic basis of cognitive impairments in ADHD, there are some limitations to note. The sample sizes for individual research sites were relatively small, and the study only included participants of European ancestry. Larger and more diverse samples will be important for replicating and extending these findings. Additionally, other types of genetic variation not captured by common variant polygenic risk scores may also play a role in ADHD-related cognitive difficulties.

Nonetheless, this research represents a significant step in connecting genetic risk for ADHD to specific cognitive processes. A better understanding of how genetic factors shape different aspects of the disorder could potentially inform more targeted treatments and interventions in the future. For now, the findings highlight the complex nature of ADHD’s genetic underpinnings and the importance of considering distinct cognitive processes rather than just overall diagnosis.