How Much Do Genes Influence Impulsivity and Compulsivity?

What you need to know

• Impulsivity and compulsivity are traits related to many mental health issues, including addiction and obsessive-compulsive disorder.
• This study looked at how much genes versus environment influence impulsive and compulsive traits in adult twins.
• The researchers found modest genetic effects for impulsivity and obsessiveness, but environmental factors seemed more important for a general impulsive-compulsive trait.
• Understanding these influences could help develop better treatments for related mental health conditions.

Understanding impulsivity and compulsivity

Impulsivity refers to a tendency to act quickly without thinking things through. Compulsivity involves repetitive behaviors that a person feels driven to perform. While these traits were once thought to be opposites, researchers now believe they overlap in important ways.

This study examined impulsivity and compulsivity as overlapping traits that exist on a spectrum in the general population. The researchers were interested in how much these traits are influenced by genetics versus environmental factors.

How the study worked

The study included 173 pairs of adult twins from Australia. Participants completed questionnaires measuring different aspects of impulsivity, compulsivity, and related traits like intolerance of uncertainty.

Using twin studies allows researchers to estimate how much of the differences between people on a trait are due to genes versus environment. This works because:

• Identical twins share 100% of their genes
• Fraternal twins share about 50% of their genes
• Both types of twins typically share very similar environments growing up

By comparing how similar identical versus fraternal twins are on a trait, researchers can estimate its heritability - how much of the differences between people are due to genetic factors.

Key findings

The researchers identified three key traits:

1. A general “impulsive-compulsive” trait combining aspects of both impulsivity and compulsivity
2. A more specific impulsivity trait
3. A more specific obsessiveness trait

For the general impulsive-compulsive trait, environmental factors shared by twins (like family environment) seemed most important, accounting for about 36% of the differences between people. Genetic factors did not appear to play a major role.

For the specific impulsivity trait, genes accounted for about 33% of the differences between people. This suggests impulsivity is moderately heritable.

For obsessiveness, the results were less clear. Genes may account for about 25% of the differences, but shared environment could also explain a similar amount. The data wasn’t strong enough to determine which was more important.

What this means for understanding mental health

These findings suggest that while there are some genetic influences on impulsive and compulsive traits, environmental factors play a very important role - especially for the general tendency to be both impulsive and compulsive.

This is actually good news from a treatment perspective. It means that these traits are likely quite modifiable through therapy, lifestyle changes, or other interventions. If they were highly genetically determined, they might be more difficult to change.

The general impulsive-compulsive trait identified in this study may reflect a broad risk factor for developing various mental health issues like addiction or obsessive-compulsive disorder. Since it seems strongly influenced by environment, identifying and modifying relevant environmental factors could potentially help prevent or treat these conditions.

Limitations to keep in mind

This study had a relatively small sample size for a twin study, which limited the researchers’ ability to draw firm conclusions in some cases. The results should be confirmed in larger studies.

The study relied on self-report questionnaires, which can be affected by participants’ insight and honesty. Using additional measurement methods in future research could provide a more complete picture.

The study only included adult twins, so the results may not apply to children or adolescents. How genetic and environmental influences change across the lifespan is an important area for future research.

Conclusions

• Both genetic and environmental factors influence impulsive and compulsive traits, but environmental influences may be especially important.
• A general tendency to be both impulsive and compulsive seems particularly influenced by shared environmental factors.
• These findings suggest interventions targeting environmental factors could potentially help prevent or treat mental health conditions related to impulsivity and compulsivity.
• More research is needed to identify specific environmental factors that influence these traits and to confirm these findings in larger, more diverse samples.

Understanding the complex interplay of genetic and environmental influences on traits like impulsivity and compulsivity is an important step toward developing more effective, personalized approaches to mental health treatment and prevention.