Would you rather have $10 today or $20 in a month? Your answer to this classic question gets at the heart of a trait known as delay discounting: our tendency to devalue larger future rewards in favor of smaller more immediate rewards. This trait isn’t just about money; it reflects a tendency that can influence decisions about our health, finances, and relationships.
For years, scientists have known that our genetics play a role in delay discounting, but they needed data from more people to gain meaningful insights. Previously, 23andMe scientists collaborated with researchers at the University of California, San Diego to conduct the first-ever genome-wide association study of delay discounting. Now, in a recently published study, the 23andMe Research Institute and UC San Diego teams, along with researchers at other institutions, have increased the number of research participants more than five-fold, creating an even clearer picture of the genetics of delay discounting.
Uncovering New Genetic Clues
The power of genetic research often lies in numbers. This study used data from over 134,000 consented 23andMe research participants. This huge increase allowed the researchers to identify 14 distinct genetic variants significantly associated with delay discounting, a big step up from the previous handful of known genetic associations.
Finding these genetic variants is a crucial first step. It gives researchers specific biological regions to investigate in order to understand the underlying neurobiology of why some people are more present-focused while others can more easily wait for a bigger payoff.
A Web of Connections: Health, Behavior, and Genetics
This research also explored how the genetics of delay discounting overlap with 73 other complex traits, confirming some expected connections and revealing some surprising new links.
One of the most consistent findings was a strong genetic correlation with smoking behaviors. The genetic variants associated with steeper delay discounting (meaning a stronger preference for immediate rewards) were also linked to a higher likelihood of starting to smoke and greater difficulty quitting. This aligns with previous studies that showed that delay discounting is associated with the risk of relapse especially for nicotine addiction.
However, the story isn’t as simple as it might seem. The researchers found significant negative genetic correlations with several psychiatric and neurodevelopmental conditions, including obsessive-compulsive disorder, anxiety, schizophrenia, and autism spectrum disorder. This suggests that the genetic factors that predispose a person to wait for a later reward may overlap with genetic risks for these conditions.
Finally, the researchers analyzed data from a separate hospital-based cohort of nearly 73,000 individuals and found that a polygenic score for delay discounting was associated with 246 different medical conditions. While some of these links are likely due to behaviors associated with delay discounting (like smoking), others (like for cardiovascular or metabolic traits) may point to shared biological mechanisms. Together this suggests the genetics of delay discounting is intertwined with other conditions, and could have far-reaching impacts on our overall health.
Important Considerations and the Path Forward
It’s crucial to remember that correlation does not equal causation. While this study found genetic overlaps, we can’t say that delay discounting causes these other traits or vice-versa. The relationship can be complex and even bidirectional. For instance, we know substance use can increase impulsive decision-making, but steeper delay discounting also predicts who is more likely to use substances in the first place.
Like all scientific research, this study also has its limitations. This analysis was conducted on research participants of European descent, and 23andMe research participants tend to be more educated, older, and have a higher socioeconomic status than the general population. Future studies in more diverse populations are essential to ensure the findings are applicable to everyone.
Despite these caveats, this work marks an important step forward and lays the foundation for future studies aimed at discovering better prevention strategies, diagnostic tools, and treatments for a whole host of conditions linked to the fundamental human trait of deciding between ‘now’ and ‘later.’
