The discovery of a gene variant associated with opioid addiction in African Americans may lead to personalized methadone treatment, according to HealthDay.

The gene variant helped identify African Americans who might need higher doses of methadone. Patients receiving methadone treatment for opioid addiction vary widely in their dose requirements, the researchers note. Too high of a dose can cause sedation and dangerous breathing difficulties, while too low of a dose can lead to relapse.

“Opioid addiction has become a national epidemic, and improving the effectiveness of medical therapies has to be a priority,” study lead author Andrew Smith of Yale University said in a news release.

The same gene variant was also found to predict the morphine dose needed to achieve effective pain control in African American children undergoing surgery. The findings are published in the journal Molecular Psychiatry.