When the UK reclassified cannabis to a lower penalty category in 2004, there were no increases in cannabis use, other drug use, crime, or other risky behaviors.
Read this if you want evidence on whether reducing cannabis penalties leads to more drug use and crime.
No increases in cannabis use, other drugs, or crime after UK declassification
What the researchers found
Researchers exploited the 2004 UK declassification of cannabis (from Class B to Class C) as a natural experiment to test whether reduced penalties led to increases in drug use or crime. Using individual-level panel data from England and Wales (2003-2006), they compared outcomes across age groups that were differently affected by the penalty changes due to thresholds in British criminal law.
The difference-in-differences analysis found essentially no increases in cannabis consumption, use of other drugs, crime, or other forms of risky behavior following declassification. The null findings were consistent across multiple outcome measures.
Why it matters
A central concern about cannabis policy reform is that reducing penalties will increase use and associated harms. This study provided empirical evidence from a national-level policy change that declassification did not produce the feared increases.
The numbers in context
Data covered 2003-2006 in England and Wales. No significant increases were found in cannabis use, other drug use, crime, or risky behavior following the 2004 declassification.
How the study worked
Quasi-experimental study using individual-level longitudinal panel data from the Offending, Crime and Justice Survey (2003-2006). Difference-in-differences design exploited the fact that the 2004 cannabis declassification changed expected punishments differently across age groups due to legal thresholds.
What this study cannot tell us
The UK declassification was a relatively modest policy change (reclassification, not full legalization). The three-year follow-up may not capture longer-term effects. The specific age-based threshold approach relies on assumptions about how different groups perceived the policy change. UK findings may not generalize to other legal and cultural contexts.
How to read the evidence
Quasi-experimental design using a natural policy experiment with individual-level longitudinal data, providing stronger causal evidence than cross-sectional studies.
When this study was published
Published in 2014 analyzing the 2004 UK policy change. Cannabis was later reclassified back to Class B in 2009.
The bigger picture
This study joined a body of evidence suggesting that criminal penalties are not the primary driver of cannabis use rates. The finding is relevant to ongoing debates about cannabis decriminalization and legalization worldwide, though the UK context (temporary reclassification later reversed) is specific.
Questions still open
- Would full legalization (not just declassification) produce different results? Did the later reversal of the reclassification affect use patterns? Do these null findings hold in countries with different baseline use rates and cultural attitudes toward cannabis?
Common questions
Does reducing cannabis penalties increase use?
Does cannabis declassification lead to more crime?
Read the original research
Cannabis depenalisation, drug consumption and crime - evidence from the 2004 cannabis declassification in the UK.
Social science & medicine (1982), 115, 29-37
Citation
Braakmann, Nils; Jones, Simon. (2014). Cannabis depenalisation, drug consumption and crime - evidence from the 2004 cannabis declassification in the UK.. Social science & medicine (1982), 115, 29-37. https://doi.org/10.1016/j.socscimed.2014.06.003