Preeminent doctor-turned-journalist and Emmy winner Sanjay Gupta of CNN came out with a powerful mea culpa on marijuana legalization this morning, personally apologizing for his role in opposing the little green plant. Dr. Gupta had previously opposed the use of marijuana because of its purported dangers, but has changed his tune on almost every statement he has made.

"Reading these papers five years ago, it was hard to make a case for medicinal marijuana. I even wrote about this in a TIME magazine article, back in 2009, titled 'Why I would Vote No on Pot.'" 

Sanjay Gupta marijuana weedIn an effort to build buzz for his documentary, which premieres Sunday night, Gupta has been sharing his blunt talking points with Katie Couric on ABC NewsPiers Morgan on CNN, and Craig Ferguson on the Late Late Show. He also admitted to what CNN called a "shocking revelation," that he and Piers Morgan had smoked weed before (GASP!).

What did Gupta actually say that he wants to apologize for? Well, quite a lot, actually, and the new version of Gupta rejected almost every argument that old Sanjay Gupta once made.

On Marijuana's Dangers

Then:

In the 2009 Time Magazine article, Gupta explained why "marijuana isn't really very good for you": 

Frequent marijuana use can seriously affect your short-term memory. It can impair your cognitive ability (why do you think people call it dope?) and lead to long-lasting depression or anxiety. While many people smoke marijuana to relax, it can have the opposite effect on frequent users. And smoking anything, whether it's tobacco or marijuana, can seriously damage your lung tissue.

And in a 2002 interview with CNN anchor Bill Hemmer, he noted the links between marijuana use and schizophrenia and depression.

But the three studies you are talking about talk specifically about schizophrenia and depression, and the fact that marijuana use earlier in life actually may lead to an increased -- 30 percent increase -- in schizophrenia later in life.

...

Schizophrenia is a very complicated diagnosis ... The fact that this THC can actually cause these things is just becoming known now.

Now:

"As much as I searched, I could not find a documented case of death from marijuana overdose."

On Marijuana's Benefits

Then:

In that 2002 CNN interview:

And marijuana can offer some of those things, especially when it comes to reducing nausea and vomiting, [though I'm] not advocating that necessarily myself. I think there are other ways to do that besides marijuana. There are a lot of short-term effects which may be hard to get around.

Now:

In Gupta's column:

[T]here are very legitimate medical applications. In fact, sometimes marijuana is the only thing that works.

On Piers Morgan's show, speaking about an expert against marijuana legalization.

He seemed to concede that it has no medical benefit whatsoever. That's not true. We know that there is medical benefits.

On Marijuana's Addictive Powers

Then:

In the 2009 Time piece:

Why do I care? As Dr. Nora Volkow, director of the National Institute on Drug Abuse, puts it, "Numerous deleterious health consequences are associated with [marijuana's] short- and long-term use, including the possibility of becoming addicted."

Now:

On Piers Morgan's show:

"This idea of high abusive or addictive potential: It can be addictive, but as opposed to other things  ... a lot of it smacked of a lot of propaganda, Piers."

In Gupta's own column this morning:

[I]t is hard to make a case that it has a high potential for abuse. The physical symptoms of marijuana addiction are nothing like those of the other drugs I've mentioned.

So at what point in his research did he change his mind on marijuana? A June 2009 interview with Anderson Cooper suggests a shifting opinion, as Gupta lists studies of both positive and negative impacts of weed on people. He accepts both sides of the argument, and does not take a definitive stance either way.

Marijuana Sanjay GuptaIn November 2010, on Cooper's show again, he again speaks without taking a strong opinion either way. Cooper asks whether a recent report on the rising amount of THC in marijuana is bad, and Gupta responds: "It kind of depends who you ask. There's pretty charged people on both sides of this issue." Cooper then asks if pot is addictive. "Well, some people say it is, and some people it's addictive to the point where it might be a gateway drug, but that is also a controversial point." Is pot bad for kids? "But again it is hard to say for sure with any conviction that those side effects last into the future or long-term."

He appeared to be debating within himself in these interviews. Now, though, Gupta says he has made up his mind. And it sounds like it's for good.

Photo of Gupta: REUTERS/Lucas Jackson

Photo of Marijuana plant: AP Photo/Alexandre Meneghini