Back in 1894 - 1895, Parliament set up a commission to investigate the prevalence of cannabis use in the Indian subcontinent, and to make recommendations on how it should be addressed.

The Commission interviewed over 1,000 witnesses and produced a seven volume, 3,500 page report, which concluded that:

"Total prohibition of the cultivation of the hemp plant (i.e. cannabis) for narcotics, and of the manufacture, sale or use of the drugs derived from it, is neither necessary or expedient in consideration of their ascertained effects, of the prevalence of the habit of using them, of the social and religious feeling on the subject, and of the possibility of its driving the consumers to have recourse to other stimulants or narcotics which may be more deleterious

...

The means to be adopted for the attainment of [control and restriction are:

- adequate taxation, which can be best effected by the combination of a direct duty with the auction of the privilege of vend

-prohibiting cultivation, except under license, and centralising cultivation" (Emphasis added)

The Commission were spot on in their assessment that prohibition might lead consumers to have recourse to more "deleterious" narcotics:

1. Synthetic cannibinoids aka "Spice" only took hold because they were, temporarily, legal, meaning that they were more readily available to some consumers (e.g. on the Isle of Jersey, or in rural parts of the Midwest USA) and/or did not carry the threat of arrest, and weren't detected by drugs tests (which is one of the reasons why they have taken such a firm grip on prisons, which routinely drug test prisoners) Their effects are much more unpredictable than actual cannabis, and in many cases, much more unpleasant and severe, with reports of physical withdrawal symptoms (aka "rattling") and overdose symptoms (kidney damage) entirely unknown with actual cannabis.. The USA has no equivalent of the  Psychoactive Substances Act, which means that certain synthetic cannabinoids remain legal in the US, but unsurprisingly there is almost no market  for them in states where cannabis is either fully legal or widely available and decriminalised.

2. Prescription Opioids. US states with medical marijuana laws have markedly lower opioid prescription rates and opioid abuse rates. In part this is because recreational users have a safe alternative to raiding Grandma's opioid stash for a high. In part this is because patients with back pain, arthritis etc. have a safer alternative to opioids for medicating their pain.

3. The development of "skunk". The selective breeding of high THC, low - CBD cannabis, which carries a greater risk of causing anxiety, paranoia, etc, solely occurred under the black market, as producers of a contraband product have a clear incentive to produce the highest potency product possible (i.e. the most active ingredient per square cm of material which you have to hide from the feds) - hence why during prohibition there were lots of "Moonshine" stills producing high strength alcohol and absolutely no illegal beer brewers up in the Kentucky hills.

 

There it all was, set out in black and white 125 years ago by the Victorians.