A large twin study suggests that while generalized anxiety symptoms often fluctuate from year to year during early adulthood, there is a stable core to these symptoms that is strongly shaped by genetic factors. The findings, published in Psychological Medicine, indicate that around 60% of the stability in anxiety from ages 23 to 26 can be explained by genetic influences. Meanwhile, environmental experiences appeared to play a bigger role in the short-term ups and downs of anxiety over time.
The research also provides evidence that anxiety in young adulthood tends to cluster into two distinct dimensions: physical distress and a pattern involving excessive worry and avoidance. Interestingly, the two symptom dimensions were found to share much of their genetic basis, even though they differed somewhat in how environmental influences shaped them.
Heritability is a measure used in genetics to estimate the proportion of variation in a trait—like anxiety—that can be attributed to inherited genetic differences between people. A heritability estimate of 60%, for example, does not mean that a person’s anxiety is 60% determined by their genes. Instead, it means that, across a population, 60% of the variation in a given trait can be linked to genetic differences.
This concept helps scientists identify which traits are more likely to have a strong genetic basis, which in turn can inform research into biological mechanisms and guide future treatment strategies.
Rates of anxiety have increased significantly among young adults in recent years, raising public health concerns. But while there is extensive research into anxiety in childhood and adolescence, fewer studies have explored how anxiety symptoms evolve during the twenties—a period marked by major life transitions, such as entering the workforce or living independently for the first time.
The researchers wanted to understand how much of generalized anxiety during this time of life is driven by genetics versus environmental factors. They were also interested in whether anxiety symptoms in early adulthood tend to fall into distinct categories, and whether those symptom clusters are shaped by different underlying causes.
“Anxiety symptoms are common among young adults and have become more prevalent in this age group in recent years, especially among females,” said study author Geneviève Morneau-Vaillancourt, Banting Postdoctoral Fellow at the Centre for Research at the Institut universitaire en santé mentale de Montréal and the School of Criminology at the Université de Montréal.
“Because we know that anxiety is heritable, it is important to understand how genetic factors influence its development during the early twenties—a life stage marked by important social, academic, and occupational transitions. The Twins Early Development Study (TEDS) offered a unique opportunity to examine the development of generalized anxiety in young adulthood, providing rich longitudinal data from six assessments between ages 23 and 26 (which were partly collected during the COVID-19 pandemic). The twin design also enabled disentangling genetic from environmental influences.”
The Twins Early Development Study is a long-term project tracking twins born in England and Wales in the mid-1990s. For this analysis, the team focused on data collected from 6,429 twin pairs between the ages of 23 and 26. Each participant completed a questionnaire measuring the severity of generalized anxiety symptoms on six occasions across this age range.
The team applied statistical models that are commonly used in twin studies to tease apart genetic and environmental influences. Because identical twins share all of their genes and fraternal twins share about half, comparing how similar each group is on a given trait allows researchers to estimate the degree of heritability.
They also looked at whether anxiety symptoms could be separated into different types using factor analysis, a method that identifies patterns of symptoms that tend to occur together. After identifying the symptom dimensions, the team repeated their genetic modeling separately for each dimension.
One of the central findings is that while generalized anxiety symptoms do vary over time, they also show considerable stability across early adulthood.
“Anxiety in the early twenties is common, and it matters,” Morneau-Vaillancourt told PsyPost. “These years are a sensitive period for mental health. Anxiety levels were moderately stable between ages 23 and 26, meaning that they also fluctuated over time.”
Genetic factors were the main contributor to this stable core. The researchers created a “latent stability factor”—a statistical representation of the trait that captures what remains consistent across time—and found that this factor had a heritability of about 60%. This is notably higher than the heritability estimates for anxiety at any single time point, which ranged between 39% and 46%.
In contrast, changes in anxiety symptoms over time were more strongly linked to non-shared environmental factors—those that differ between twins and might include life events, personal relationships, or daily stressors. These findings suggest that while someone’s underlying tendency to be anxious may be relatively stable and influenced by their genes, the expression of that anxiety can shift depending on what’s happening in their life.
“Genetics play a role, but they’re not the whole story,” Morneau-Vaillancourt said. “We found that the stability in generalized anxiety between ages 23 and 26 was largely due to genetics, whereas change was mostly explained by environmental influences.”
The study also found that anxiety symptoms in young adults consistently grouped into two main dimensions. One set of symptoms reflected “somatic distress,” such as physical tension or restlessness. The other was labeled “worry-avoidance,” which included excessive worrying and efforts to avoid stress-inducing situations.
While these two dimensions were distinct on the surface, they shared most of their genetic influences. That suggests that they may arise from the same underlying biological vulnerabilities. However, their environmental influences were less overlapping, indicating that different life experiences may shape how anxiety shows up in different people.
These findings have several implications for how scientists approach the genetics of anxiety. Studies that rely on single time points may underestimate the role of genes by capturing only a snapshot of someone’s symptoms. By instead focusing on stable patterns that persist over time, researchers may be able to increase the chances of identifying genetic variants that contribute to anxiety.
The study also points to the importance of considering both stability and change when trying to understand what drives anxiety. While genetic predispositions provide the foundation, environmental experiences—such as job stress, financial uncertainty, or social changes—may push anxiety levels up or down at different times. Notably, the study found evidence of stable environmental influences as well, suggesting that some life circumstances may have long-term effects on anxiety symptoms.
“Even if genetics play a role, it doesn’t mean that anxiety is inevitable,” Morneau-Vaillancourt explained. “It indicates that some individuals may have a higher probability than others of developing anxiety. Environment, life experiences, and coping strategies matter too and could make a difference.”
Because four out of the six data collection points occurred during the COVID-19 pandemic, the researchers also considered how this context might have influenced their results. While the overall structure of anxiety symptoms and the patterns of genetic and environmental influence remained stable, average anxiety levels were higher during the pandemic.
A new set of genetic effects appeared around the time of the first pandemic wave, possibly reflecting how stressful global events might interact with genetic predispositions in unique ways. The authors caution that more research is needed to separate age-related changes from pandemic-related effects, especially given the unusual timing of the study.
The study had a few limitations. The time gaps between survey waves varied, which might have affected how well changes and continuities were captured. Most of the data were collected during the pandemic, which may limit the generalizability of the findings to more typical circumstances. The researchers also used a less common anxiety questionnaire, which, while reliable, may make it harder to compare their results with other studies that use more standard tools.
Finally, the study focused only on young adults. To better understand how anxiety develops across the lifespan, future research will need to extend this kind of work into adolescence and the thirties and beyond.
The study, “Heritability of generalized anxiety stability: a longitudinal twin study among young adults,” was authored by Julia Funk, Geneviève Morneau-Vaillancourt, Elisavet Palaiologou, and Thalia C. Eley.
