Addiction treatment is most successful when it lasts more than 30 days, according to researchers at the University of Southern California. They found after one year, the treatment success rate was 55 percent for those who underwent a 30-day treatment program, and 84 percent for those in treatment programs that lasted longer.

The 72 people in the study were being treated for a variety of addictions, including opioids, amphetamines, benzodiazepines and alcohol, HealthDay reports.

Most government and private health insurance programs only reimburse patients for 30 days of addiction treatment, according to study leader Dr. Akikur Mohammad of the University of Southern California. “Aftercare is crucial once an individual has completed drug or alcohol treatment and is in recovery. There is a continuity of care that should be followed once initial treatment is completed,” he said.

The study appears in the Open Journal of Psychiatry.