A twin study of self-reported criminal behaviour

Area of Science:

• Behavioral Genetics
• Criminology
• Psychiatry

Background:

• Twin studies are crucial for dissecting genetic and environmental influences on individual differences.
• Understanding the etiology of criminal behavior requires differentiating genetic, shared, and non-shared environmental impacts.

Purpose of the Study:

• To analyze the contributions of genetic and environmental factors to criminal behavior using twin data.
• To investigate the persistence of environmental influences on criminality after leaving a shared environment.

Main Methods:

• Utilized self-reported data on arrests and criminal behavior from the Vietnam Era Veteran Twin Registry.
• Analyzed data from 3226 male twin pairs who served in the military during the Vietnam era.

Main Results:

• Both genetic factors and the common environment significantly influenced early arrests.
• Genetic factors, not the common environment, significantly predicted later criminal behavior (ever arrested, multiple arrests).
• The common environment influenced early criminal behavior, but this effect did not persist after leaving the shared environment.

Conclusions:

• Genetic factors play a probabilistic role in criminal behavior by influencing individual dispositions.
• Shared environmental influences on criminality are significant only while the environment is actively shared.
• Genetic predispositions are more critical for long-term criminal behavior than shared environmental factors.