It is not a character flaw; it is a chronic disease.
Relapse rates are on par with more socially acceptable chronic diseases like diabetes or heart disease.
Drug addiction is heritable.
And it is established easiest in developing brains.
Finding the needle in the haystack with endophenotypes
Addiction is a heritable disease—genetic research estimates between 40 and 60 percent—and is also linked to personality types, which are also heritable. Traditional molecular genetic research, which attempts to linkgenes to clinical outcomes (i.e. disease), has yet to identify genes specifically associated with addiction.
Leading addiction researchers, including Volkow, encourage the study of endophenotypes, where behavioral traits associated with diseases are used to help identify clinically relevant genes. Studying genes associated with behavioral traits that are themselves linked to diseases should be more successful than directly linking a gene to the disease.
Personality type is a behavioral trait used to identify endophenotypes associated with addiction. Personalities with more neurotic and negative emotional tendencies (labeled NEM/N) are associated with addiction and other mental health disorders that often co-occur with drug addiction, like depression and anxiety. NEM/N personalities are also associated with variations in the serotonin transporter gene, which is one of the most studied genes in all neuroscience.
Though the NEM/N personality is associated with addiction and serotonin genes are associated with NEM/N personalities, serotonin genes have not yet been strongly linked to drug addiction! Volkow and her colleaguesuse this example to argue for “the lack of utility of directly connecting genes and clinical phenotypes” and to push for using behavior to identify biological markers of addiction.
If the important gene is the needle and the human genome is the haystack, studying endophenotypes facilities finding that needle by reducing the size of the haystack. Identifying genes associated with addiction is important because of potential treatment therapies.
The establishment of addiction and the vulnerability of growing up
Drug addiction is most likely to take root before the brain finishes developing, which for humans is the mid-20s or maybe even into the early 30s. Rats exposed to nicotine as adolescents self-administer more nicotine than rats first exposed as adults. The vulnerability ofadolescence to drug addiction is true of humans too; exposure to drugs during adolescence increases the likelihood of addiction. And adolescence is when most people experiment with drugs.