"It's been eight months since I last wrote about medical marijuana," he explains in a new column posted at cnn.com, "apologizing for having not dug deeply into the beneficial effects of this plant and for writing articles dismissing its potential. I apologized for my own role in previously misleading people, and I feel very badly that people have suffered for too long, unable to obtain the legitimate medicine that may have helped them.
"Since our documentary Weed aired in August, I have continued to travel the world, investigating and asking tough questions about marijuana.
"I am more convinced than ever that it is irresponsible to not provide the best care we can, care that often may involve marijuana. I am not backing down on medical marijuana; I am doubling down.
"I hope this next documentary will enable a more open discussion and advance science in the process…. Although the 1936 film Reefer Madness was propaganda made to advance an agenda with dramatic falsehoods and hyperbole, I hope you will find Cannabis Madness an accurate reflection of what is happening today, injected with the best current science.
"I worry that generations from now, my great-grandkids will find Internet headlines referring to me as the 'pot doc.' I do hope they will also read the rest of the story and understand the lives of the countless people who have suffered needlessly when a plant could have helped. I hope they know that I have dedicated my time to researching the medical literature, speaking to the scientists in person and piecing together a fact-based presentation meant to educate, not frighten.
"I know the discussion around this topic will no doubt get heated. I have felt that heat. But I feel a greater responsibility than ever to make sure those heated discussions are also well-informed by science."
In Weed 2, Gupta acknowledges that there have been some positive developments since Weed originally ran on CNN last August, such as Georgia's House voting in favor of a medical-marijuana bill and the NFL beginning to acknowledge that cannabis can help pain-stricken players.
Weed 2: Cannabis Madness airs on Mar. 11 at 10 pm on CNN.