All the studies show that problematic drug use is far more common in poorer communities.
There were also fewer obvious signs of problematic drug use – far fewer hollowed-out faces, no needles on the street.
"These levels of resources would be better used by the police in targeting real problematic drug use, or on education and treatment," he said.
Most problematic drug use is related to stress, trauma, genetic predisposition, mild or serious mental illness, use at an early age, or some combination of those.
The inquiry, the Liberal Democrats said, would look at reforms in Portugal which are said to have reduced problematic drug use through decriminalisation for personal use and investing in treatment centres.
But these measures reveal very little about the impact of problematic drug use, the implications of drug control efforts on people's lives or human rights violations: the very problems drug policies ostensibly are meant to address.
More extensive decriminalisation measures across Europe and beyond seem to have achieved the desired effect, reducing drug use and abuse by removing factors that create problematic drug use such as stigmatisation, lack of access to healthcare, prison sentences and employment difficulties.
For example, problematic drug use significantly predicted violent re-offending.
Additionally, 19.1% had indications of current problematic drinking, and 8.2% reported problematic drug use.
People with mental health disorders and problematic drug use are over-represented in the prison system.
For the JJIs, being involved in research to decrease substance abuse can draw attention to problematic drug use among juvenile delinquents in general, but also to the possibility that problematic drug use continues within the walls of the JJIs.
