Many police officers feel their efforts to enforce the law on possession of cannabis have "little or no impact" on offenders' use of the drug, according to a study.
Researchers from the University of York looked at data from thousands of drug offences dealt with by North Yorkshire Police between 2013 and 2016, and interviewed 37 officers about their experience of policing cannabis possession.
The research concluded: "Most said that cannabis policing had little or no overall impact on offenders. Nonetheless, many referred to particular groups or instances where an impact might be made - especially on young people early in their drug careers.
"Many officers saw cannabis use as a significant problem and several specifically mentioned the importance of trying to prevent escalation into 'harder' drug use."
It said several officers pointed out that "ultimately, they could not know what impact their policing was having, and for many, the question was irrelevant in the sense that it was simply part of their job and something they had to do".
North Yorkshire has one of the lowest crime rates in the UK but it is much higher ranked for drugs offences, the majority of which were for cannabis possession.
The research found: "While interviewed officers were largely happy with the disposals available to them for dealing with adults, there was widespread frustration with the limited options when dealing with young people.
"The majority of officers did not want to criminalise young people, wanting instead to divert them to disposals that would help them with their drug use."