How Does Socioeconomic Status Affect the Genetic Links Between Mental Health Conditions?

What you need to know

Socioeconomic status (SES) has genetic links to mental health and substance use disorders
Accounting for SES-related genetic factors changes our understanding of how different mental health conditions are genetically related
This research helps separate genetic risks specific to mental health from those related to broader socioeconomic factors

How are mental health conditions genetically linked?

Many mental health and substance use disorders tend to occur together in the same individuals or families. Researchers have found that part of this co-occurrence is due to overlapping genetic risk factors. In other words, some of the same genetic variants that increase risk for one condition also increase risk for others.

However, mental health conditions are also associated with socioeconomic status (SES) - factors like education level, income, and neighborhood environment. SES itself is partly influenced by genetics. This raises an important question: are the genetic links between different mental health conditions due to shared biology specific to those conditions, or are they partly explained by broader genetic factors related to SES?

Examining the role of SES

To explore this question, researchers analyzed genetic data from large studies of 16 mental health traits, including psychiatric disorders like depression and schizophrenia, as well as substance use behaviors like smoking and alcohol consumption. They also looked at genetic data related to three indicators of SES:

Educational attainment (years of schooling completed)
Household income
Neighborhood deprivation (a measure of socioeconomic disadvantage in a geographic area)

Using advanced statistical techniques, the researchers created a composite measure of “genetic SES” that captured the shared genetic influences across these three SES indicators. They then examined how accounting for this genetic SES factor changed the apparent genetic relationships between different mental health traits.

Key findings

SES has widespread genetic links to mental health

All 16 of the mental health traits showed significant genetic correlations with the SES factor. This means that many of the genetic variants associated with higher or lower SES also influenced risk for mental health and substance use issues.

Notably, the direction of these relationships varied:

Conditions like ADHD, anxiety, depression, and smoking behaviors were genetically linked to lower SES
Other traits like anorexia nervosa, autism spectrum disorder, and frequency of alcohol consumption were genetically associated with higher SES

Accounting for SES changes our view of genetic risks

When the researchers statistically removed the effects of SES-related genetic variants, it significantly altered the picture of genetic risk for mental health conditions:

The estimated heritability (proportion of risk due to genetics) decreased for many traits, especially ADHD
The apparent genetic overlap between different mental health conditions often became weaker
In some cases, genetic correlations between traits increased after accounting for SES

For example, ADHD and cannabis use initially appeared to have a weak positive genetic correlation. But after removing SES-related genetic effects, this relationship became much stronger. This suggests that some genetic links between mental health traits may actually be masked by opposing relationships with SES.

Psychiatric vs. substance use traits

The researchers found that accounting for genetic SES factors had different effects on psychiatric disorders compared to substance use behaviors:

Genetic correlations between different substance use traits generally decreased
The group of psychiatric disorders remained more tightly genetically linked
ADHD showed a unique pattern, becoming more genetically similar to substance use traits than other psychiatric disorders

Why this matters

This research helps disentangle the complex relationships between genetics, socioeconomic factors, and mental health. The findings have several important implications:

Refining our understanding of shared risk

By separating out genetic effects related to SES, we can get a clearer picture of which genetic factors are more specific to mental health conditions themselves. This could help identify biological mechanisms that are truly shared across different disorders.

Improving genetic risk prediction

Genetic risk scores are increasingly used to predict individuals’ likelihood of developing various health conditions. This work suggests that accounting for SES-related genetics could make these predictions more accurate and specific.

Informing debates on diagnostic categories

Psychiatric diagnoses are based on observed symptoms and behaviors. The genetic clustering of disorders provides another perspective on how to group and distinguish between conditions. This research suggests that apparent genetic similarities between disorders may sometimes be driven by shared links to SES rather than shared disease-specific biology.

Highlighting the complexity of gene-environment interplay

While we often think of SES as an environmental factor, this study reinforces that there are genetic influences on socioeconomic outcomes. These SES-related genetic factors then shape people’s environments in ways that impact mental health. This illustrates the complex back-and-forth between genetic risks and environmental contexts.

Limitations and next steps

It’s important to note some limitations of this work:

The study relied on data primarily from individuals of European ancestry. The genetic relationships may differ in other populations.
The measures of SES were limited. Future work could incorporate more detailed socioeconomic indicators.
This type of genetic analysis can’t definitively determine cause-and-effect relationships.

Follow-up studies could:

Examine how these genetic relationships play out over the course of people’s lives
Investigate whether interventions targeting SES-related factors could help prevent mental health issues in genetically at-risk individuals
Explore similar patterns for other health conditions beyond mental health

Conclusions

Genetics plays a role in both socioeconomic status and mental health, with many genetic factors influencing both
Accounting for SES-related genetics significantly changes our understanding of the genetic relationships between mental health conditions
This work helps distinguish between genetic risks specific to mental health and those related to broader socioeconomic factors
The findings highlight the complex interplay between genetic risks, socioeconomic environments, and mental health outcomes

By shedding light on these intricate relationships, this research takes an important step toward a more nuanced understanding of the genetic architecture of mental health. Ultimately, this knowledge could inform more effective prevention and treatment strategies that account for both biological risks and socioeconomic contexts.