Everybody must get stoned! Sang Bob Dylan back in the lazy hazy days of the mid 1960s. In that respect, it was clear from walking around Amsterdam last week, where I was covering a research conference on addiction, that not much has changed. And yet, as my Feature on bmj.com finds, there is suddenly so much innovation, both in how we regulate the cannabis trade and in the technologies that deliver the drug, that it’s causing huge uncertainty about whether we are sleep walking into a big public health mess.

E-cigarettes, for example, are reportedly taking off massively in the US, not just with nicotine but with hash oil. This, says Susan Weiss, of the US National Institute on Drug Abuse, is “putting people into contact with high concentrations of THC (the psychoactive compound in cannabis) of up to 75-90%. We have no idea what the health consequences are at this sort of potency, and we need to watch this very carefully.” As well as these e-reefers, other new disruptive technologies are rapidly emerging in the US, such as discreet mini-vaporisers, which are odourless, smoke-less, and very potent.

These new delivery systems are emerging at a time when some US states have legalised the production and sale of cannabis, notably Colorado, where a new large scale commercial industry has sprung up. It’s made popular such products as “edibles” containing THC, including “sour gummi bears” and “watermelon tarts.” People like Weiss point to a “perfect storm,” where loosening restrictions on cannabis in combination with new ways to consume cannabis at a higher potency could lead to an epidemic of health problems.

I wonder what the subject of this week’s BMJ Confidential makes of this topic? Theresa Marteau, director of the Department of Health’s policy research unit on behaviour and health, based at Cambridge University, “wants to change our minds about changing behaviour.” The public is more likely to change bad health habits where intervention is least intrusive, she says.

Asked to name the single unheralded change that has made the most difference in her field, Marteau says: “Personalised feedback from biomarker tests, including genome-wide association tests.” Why? Because they have “provided some of the best evidence that information does not lead people to stop smoking, eat or drink less. From this evidence, we can focus our efforts to change behaviour on less conscious processes activated by the environment.”

Rebecca Coombes is the magazine editor, The BMJ.