The Department of Health and Social Care (DHSC) linked drug and alcohol treatment data from the National Drug Treatment Monitoring System (NDTMS) to offending data from the Police National Computer (PNC), managed by the Ministry of Justice (MOJ).

We used this linked data to analyse the offending rate of people in the year before starting treatment and the reoffending rate in the year after starting treatment.

The main findings were as follows.

About two-thirds (67%) of the people in community-based drug and alcohol treatment in NDTMS had an exact match to a record on the PNC database. This compares with 9.4 million working-age individuals with a nominal record on the PNC in August 2024, equivalent to almost 1 in 4 of the working-age population.

People in treatment for opioids and crack were most likely to have offended in the year before treatment (20.7%), while those treated for alcohol only were least likely (11.1%).

People in treatment for opioids and crack had the highest average number of offences per offender (4.9). People in treatment for alcohol only had the lowest average number of offences per offender (2.4).

People who successfully completed or remained in treatment were less likely to reoffend in the year after starting treatment than people who did not complete treatment.

People in treatment for opioids and/or crack were more likely to have reoffended in the year after starting treatment, compared with people in treatment for other substances.