Addiction vulnerability is an individual's risk of developing an addiction during their lifetime. There are a range of genetic and environmental risk factors for developing an addiction that vary across the population.[2][4][5] Genetic and environmental risk factors each account for roughly half of an individual's risk for developing an addiction;[2] the contribution from epigenetic (inheritable traits)[6] risk factors to the total risk is unknown.[4] Even in individuals with a relatively low genetic risk, exposure to sufficiently high doses of an addictive drug for a long period of time (e.g., weeks–months) can result in an addiction.[2] In other words, anyone can become an individual with a substance use disorder under particular circumstances. Research is working toward establishing a comprehensive picture of the neurobiology of addiction vulnerability, including all factors at work in propensity for addiction.