US NEWS: A major new study has pinpointed eleven specific regions in the human genome that play a role in why some people consistently choose smaller, immediate rewards instead of waiting for larger ones. Researchers say this discovery sheds fresh light on the biology behind impulsive decision making.
The findings, published this week in the journal Molecular Psychiatry, come from one of the largest genetic analyses ever conducted on a behavioral trait known as delay discounting. In simple terms, delay discounting measures how steeply a person discounts the value of future rewards. Someone who strongly prefers $50 today over $100 next month shows high delay discounting. The habit of choosing quick gratification has long been linked to issues such as addiction, ADHD, obesity, and certain psychiatric disorders.
A research team working with the consumer genetics company 23andMe examined genetic and behavioral data from 134,935 adults of European ancestry. Participants completed a standard task that asked them to pick between smaller amounts of money available right away and larger amounts available after a delay. The steeper the preference for the immediate option, the higher the delay discounting score.
Using genome wide association study methods, the scientists identified eleven independent genetic loci that met the strict threshold for statistical significance. These regions contain 93 distinct genes associated with the trait. Roughly one fifth of those genes cluster in a single hotspot on chromosome 16. The identified variants, mostly common single letter changes in DNA known as SNPs, collectively account for about 9.9 percent of the differences in delay discounting between individuals.
Many of the same genetic locations have previously been connected to risk taking behavior, substance use disorders, and mental health conditions. Broader analyses showed that delay discounting shares genetic influences with 73 other traits, including intelligence, years of education, executive function, body mass index, schizophrenia, depression, and externalizing behaviors.
Advanced pathway analysis revealed overlapping biological mechanisms, especially in brain development and metabolism, between delay discounting and these related conditions. On the other hand, obsessive compulsive disorder appears genetically tied to the opposite pattern of lower delay discounting.
Because the study relied entirely on participants of European ancestry, the authors caution that genetic risk scores built from these data may be less accurate in people from other populations. They call for future research that includes more diverse groups to ensure the results apply broadly.
The project marks a five fold increase in sample size over earlier genetic studies of delay discounting, giving scientists far greater power to detect meaningful associations. Experts say the work strengthens the evidence that impulsive choice has a measurable biological basis and shares genetic roots with both cognitive abilities and mental health outcomes.
