Traits common in attention deficit hyperactivity disorder (ADHD), such as distractibility or impulsivity, may have been an evolutionary advantage for our ancestors by improving their tactics when foraging for food, researchers said.
ADHD is a neurodevelopmental disorder with symptoms such as impulsivity, disorganization and difficulty focusing. While prevalence estimates have varied, diagnoses have increased in many countries, including the UK.
Now, researchers say, while some of these traits tend to be viewed negatively, they may have helped people find new spots to forage.
Dr David Barack of the University of Pennsylvania, who was the first author of the research, said the study offers a possible explanation for why ADHD is more common than expected from random genetic mutations alone and – more generally – why traits such as distractibility or impulsivity was common.
“As [these traits] was truly negative, then you would think that over evolutionary time it would be selected against,” he said. “Our findings are an initial data point, suggesting benefits in certain choice contexts.”
Writing in the journal Proceedings of the Royal Society B: Biological SciencesBarack and colleagues reported analyzing data from 457 adults who completed an online foraging game in which they had to collect as many berries as possible within eight minutes.
The number of berries obtained from each bush decreased with the number of times it was eaten.
During the task, participants could either continue to collect berries from the bushes in their original location or move to a new patch – although the latter cost them time.
The team also screened participants for ADHD-like symptoms – although they stress this was not a diagnosis – and found that 206 participants had positive results.
The researchers found that participants with higher scores on the ADHD scale spent shorter periods of time in each patch of woods than those with lower scores. In other words, they were more likely to abandon their current patch and search for a new one. The team found that such participants also scored more points in the game than those with lower scores on the ADHD scale.
The researchers said their results agree with other work that has suggested that populations with nomadic lifestyles that benefited from exploration have genes associated with ADHD.
However, they added the study had limitations, including that ADHD-like symptoms were based on self-report.
to newsletter promotion
Barack said it was necessary to carry out experiments with people diagnosed with ADHD and real-life foraging tasks, not least, since the latter would involve much more effort to move between patches than in an online game.
Michael J Reiss, a professor of science education at University College London, who was not involved in the work, said that although ADHD is linked to serious negative consequences, he and his colleagues argued this can help in situations where physical activity and quick decision-making are highly valued.
“It is wonderful to see experimental evidence from David Barack and colleagues that participants who scored high for ADHD are more likely to alter their search activities in ways that can indeed be characterized as impulsive. In our evolutionary past, such behavior could sometimes have been very beneficial,” he said.
“ADHD can be a serious problem, but it’s a big problem because of today’s environments.”
