In 2010, the STEP program was added to SAMHSA's (Substance Abuse and Mental Health Services Administration) National Registry of Evidence-based Programs and Practices (NREPP). Though they did not "approve" programs, they did rate the quality of research, and STEP received a favorable review in all areas.
In 2015, they adjusted their requirements for review and inclusion in the registry. STEP was re-reviewed and received a favorable review of "promising" under these new standards and was listed as a "legacy" program (a program that previously received a favorable review).
In January of 2018, NREPP was dismantled by the current presidential administration. STEP's review is no longer available.
However, please be in touch if you require research on STEP's effectiveness!