Genetic Factors Linked to Depression and Neuroticism Associated with Reduced Voter Turnout

Historically, political scientists have emphasized environmental influences like education, income, and family background in explaining voting behaviors. However, recent twin, adoption, and molecular genetic studies indicate that factors such as political orientation and civic engagement are also partially hereditary. Integrating these findings into political science has proved challenging, particularly as initial attempts to connect specific genes to political behavior faltered when it became apparent that complex traits are influenced by numerous genetic variants, each contributing minimally.

To address these difficulties, a team of researchers including Rafael Ahlskog and Sven Oskarsson from Uppsala University, Christopher Dawes from New York University, and Aaron Weinschenk from the University of Wisconsin-Green Bay proposed the use of polygenic indices, which summarize an individual’s genetic predisposition toward specific traits.

The polygenic index is constructed by assessing hundreds of thousands of minor variations in a person’s DNA. Each variant is weighted based on its correlation with a given trait identified in extensive genome-wide association studies that often include over a million participants. By aggregating these weighted variations, researchers can generate a score that estimates an individual’s likelihood of exhibiting traits such as extraversion or high cognitive performance.

The researchers employed four major datasets to illustrate this method, including the National Longitudinal Study of Adolescent to Adult Health and the Swedish Twin Registry, involving participants with European ancestry. They gathered data on self-reported voter turnout, validated turnout from official records for both high-profile (e.g., presidential) and lower-profile elections (e.g., midterms), as well as engagement in political activities beyond voting, such as attending rallies.

Along with political data, the researchers computed polygenic indices for ten health and psychological traits encompassing aspects like cognitive performance, neuroticism, and self-rated health. They included an educational attainment genetic score for benchmarking and adhered to previously registered analysis plans.

Comparative analysis across families showed certain genetic scores associated with voter turnout. Higher genetic predispositions for cognitive performance, self-rated health, and subjective well-being were linked to increased likelihoods of voting, while neuroticism and depression scores predicted lower participation. A tendency to be a morning person correlated with higher turnout in high-profile elections, while adventurousness linked to greater turnout in lower-profile elections. Results concerning risk tolerance displayed inconsistencies, showing higher scores associated with lower turnout in high-profile elections but higher turnout in lower-profile ones.

The associations observed were modest yet significant. For instance, a one standard deviation increase in genetic scores for cognitive performance or self-rated health corresponded to about a 4 percentage point rise in voting likelihood for lower-profile elections, collectively accounting for nearly 1% of the variation in turnout.

In examining political participation beyond voting, traits linked to extraversion and adventurousness positively correlated with actions like contacting politicians or attending rallies, supporting earlier research that suggests outgoing individuals gravitate toward social political activism.

Further analyses indicated that roughly 30% of the associations with participation could be traced through the traits the genetic scores predict. However, while family comparisons suggest associations, they do not imply direct causation. The study authors identified two potential biases: population structure, where genetic differences align with social groups, and genetic nurture, which influences children’s environments based on parental genes.

To strengthen causal inference, the researchers conducted a second set of analyses focused on pairs of full siblings. This approach helped mitigate shared family environment and overall genetic differences. Many links between genetic scores and voter turnout remained intact, particularly for high-profile elections. For lower-profile elections, sibling estimates tended to be smaller, indicating earlier results may have been somewhat inflated by genetic nurture or population structure.

The authors emphasize that although genetic variations between siblings occur randomly, these within-family correlations can be interpreted causally. However, these effects do not necessarily imply that the traits the scores predict are the direct mechanisms influencing voting behavior.

They caution that genetic effects should not be seen as deterministic regarding political behavior; rather, genetic influences frequently operate through environmental pathways. For instance, a genetic inclination for height might impact political participation through socioeconomic factors rather than any intrinsic voting motivation.

Additionally, genetic scores capture only a fraction of the overall genetic influence on a trait. The current polygenic indices are affected by a dominant focus on individuals of European ancestry, limiting their applicability to diverse populations.

Future research may explore how genetic scores inform political socialization in families by comparing the genetic scores of parents and children. Additionally, the method may reveal how varying environments could amplify or diminish genetic predispositions, as preliminary analysis indicated that education might mitigate the adverse effects of depression-related genes on voting turnout.

The study, "The Genetics of Political Participation: Leveraging Polygenic Indices to Advance Political Behavior Research," was co-authored by Rafael Ahlskog, Christopher Dawes, Sven Oskarsson, and Aaron Weinschenk.