Marijuana keeps Craig Rodgers alive.

With his muscular physique and energetic, fast-talking personality, the 36-year-old Las Vegas resident seems the epitome of health — except for the banana-size scar on the left side of his head.

Rodgers was on a good career track as a trade-show organizer until 2006, when he was diagnosed with brain cancer. Now he's a passionate advocate of medical marijuana, lives on government disability, and earns a few extra bucks making candles that look like brains.

He was one of several patients who attended a conference in Tucson last month regarding the use of marijuana in medicine.

Rodgers was fishing in Canada when the first seizure struck. He was rushed from the backcountry to a hospital, but doctors didn't find the cause until three months later, after another seizure. The diagnosis is seared in his memory.

"Your tumor is here," his doctor told him while pointing at an x-ray of his head. "You're going to die."

Rodgers was given 18 months to live. Surgeons were able to remove about 80 percent of the tumor in 2007 and told him it probably would come back. They also put him on a chemotherapy regimen, which was when he "got involved in cannabis." He'd tried it a few times in his late teens and early 20s, but this experience was different.

"I took two puffs, and it was incredible," he says. "It made me feel well."

Every day, he smokes a little and eats more. Pot eases his stress and helps him sleep. It helped with the nausea that comes from the chemo drugs he's taking: "I even gained a couple [of] pounds." It helps with the "mild" pain he feels in his head. And, he says, it keeps him from having seizures.

Even more than that, Rodgers believes strongly that the pot has extended his life by slowing growth of the cancer.

The proof, he says, is that he's still alive, five years after his surgery. Still, the cancer did return and Rodgers had another surgery in December. This time, he was told there could be no more operations and that he had three years to live.

Pot, he feels, may be his best chance to beat the odds. He grows seven plants under Nevada's medical-pot law. Besides cooking pot into "edibles," making pot tea, and smoking marijuana occasionally, he also takes pot oil in pill form and turns raw weed into juice, which is rich in cannabidiol (CBD), the second-most-abundant active compound in marijuana behind delta-9 tetrahydrocannabinol (THC).

No hard evidence proves whether pot helps Rodgers' cancer. The possibility exists, nonetheless.

THC and CBD have been found in scientific studies to shrink tumors and inhibit the growth of cancer cells.

THC and other cannabinoids, including CBD, "can act as direct anti-cancer agents in multiple types of cancer" both in laboratory cultures and in the human body, according to a 2010 article in the medical journal Molecular Cancer Therapeutics. The article goes on to relate that a study showed THC and CBD were successful in treating glioblastoma, the same type of cancer that Rodgers has.

That study, conducted by researchers at California Pacific Medical Center Research and the University of California-San Francisco, was conducted in a lab and not on humans. It revealed that the combination of THC and CBD is more effective at fighting cancer than either compound alone, a finding that suggests the marijuana plant's ingredients and oils may work together to produce beneficial medical results.

"With the growing evidence showing cannabinoids are effective inhibitors of multiple types of cancer, it is likely that additional clinical trials will be carried out," wrote the authors of the California study. "Combination treatments with cannabinoids" may improve the results of such future trials.

The study didn't address questions that would be important for Rodgers' self-medicating experiment, such as how much marijuana he'd have to consume and how best to consume it to treat his cancer.

Without scientifically valid evidence, all he can do is have faith that marijuana is reducing his tumor, or at least preventing it from getting worse.

"I hope for that every single second of my life," he says grimly.

For millions of patients with cancer, chronic pain, and other maladies, the potential benefits of marijuana can't be discounted.

Many consider marijuana a wonder drug, and the list of ailments that scientists say it benefits is long.

Pot helps more with some things, like nerve pain, appetite stimulation, and nausea, and less with others, such as glaucoma. It's shown at least the potential to help with a wide range of maladies, from Parkinson's disease to arthritis.

More people use the drug these days. One survey based on self-reported information shows that 17.4 million Americans admitted using weed in 2010, up from 14.4 million in 2007. The modern medical-marijuana movement apparently is responsible for the increase.

Sixteen states and Washington, D.C., now have medical-pot laws on the books.

Because of this, people who wanted to try pot previously but were deterred because of the law can now possess it legally. In addition, older generations, who were lied to about the dangers of marijuana, are fading away, replaced by people who are more knowledgeable about the relative safety and therapeutic potential of the drug.

In Arizona, voters passed one of the most progressive medical-marijuana laws in the country, granting qualified patients the right to possess up to 2 1/2 ounces at any given time. Patients also can grow up to 12 plants at home unless a dispensary is open within 25 miles.

As of early May, the state had more than 28,000 registered patients.

Because of a failed effort by Governor Jan Brewer to derail the law, the dispensaries that legally could sell marijuana to these patients are not yet open.

The Arizona Department of Health Services, which oversees the state's pot program, took applications from would-be dispensary owners between May 14 and 25. It expects to approve many of the applications this summer. Unless the federal government intervenes, retail medical-pot stores are expected to open as soon as August, offering various strains of sativa, indica, pot-infused foods, and such concentrates as tinctures.

An aboveboard marijuana-distribution system would mean that thousands of people will have safer and regular access to their medicine, and the eventual opening of dispensaries no doubt will cause Arizonans' interest in obtaining registration cards to rise.

At the end of May, the DHS will hold hearings on whether to expand the list of qualifying ailments to include post-traumatic stress disorder, anxiety, depression, and migraine headaches.

Definitive studies haven't been conducted to determine whether pot helps any or all of these maladies, nor are scientists anywhere near a consensus on the overall potential of marijuana as a medicine.

Marijuana and medicinal products derived from it have been proved to work for a range of conditions. Yet debate rages on about how well pot works for even these ailments, and whether it and its processed forms are effective for patients.

Some advocates of the drug make claims that sound similar to those of faith healers or pushers of so-called alternative treatments, including acupuncture or powdered ginger.

The truth is, marijuana appears useful in treating some medical problems. But claims that pot can cure just about anything clearly are bogus.

Only in the past decade or so has marijuana begun to be studied scientifically, after centuries of its use as a folk remedy.

One reason is that expert analysis of the beneficial effects of pot has been stifled.

"Research surrounding cannabis that meets modern scientific standards has remained limited due to cannabis' status as a federally restricted Schedule 1 substance," wrote officials with the California Medical Association in a call to decriminalize pot last year.

The American Cancer Society's website, after mentioning that pot has been used as a medicine for 3,000 years, states: "Political and legal controversies surrounding its status as an illegal substance, as well as concerns about potentially harmful side effects, have hampered the process of scientific inquiry in many countries, including the United States."

Moral concerns surrounding the drug's recreational use have trumped honest public-safety issues when it comes to marijuana, which is less dangerous than aspirin, Tylenol, and, especially, alcohol.

The U.S. Centers for Disease Control reports that about 79,000 Americans die annually as a direct result of excessive alcohol use. More than 1,000 Arizonans die each year from accidental overdoses of prescription drugs.

Yet no reports exist of a single person ever dying from a marijuana overdose — not even a child. (That highly touted statistic could change. In recent years, emergency rooms have seen a handful of cases of babies going into comas for up to 48 hours after eating large quantities of marijuana-laced food or hashish that, presumably, their parents had left lying around. The kids apparently made complete recoveries.)

A 2003 British medical journal article by California doctor Stephen Sidney cites two studies that tracked the medical records of thousands of people for more than a decade. Both studies showed that marijuana use does not contribute to premature death.

Catchphrases along the lines of "more studies are needed" appear in many articles about the positive or negative health effects of marijuana.

Emphasizing the problem are studies with conflicting conclusions. For instance, some studies suggest pot is responsible for some cases of lung, neck, or testicular cancer; other studies show that using pot reduces — however slightly — the risk of lung, head, and neck cancer.

A major problem in doing research is that scientists, amazingly, can obtain marijuana legally (under federal law) from only one place in the country — a small farm in the Coy W. Waller Laboratory Complex at the University of Mississippi. Supplies are limited to relatively low-grade pot, not high-potency marijuana such as that found at dispensaries in Colorado and California. The lab is run by the National Institute on Drug Abuse, which partners with the U.S. Drug Enforcement Bureau and takes an open and subjective stance against marijuana use.

"They have never, in the history of their organization, provided any support to any study about marijuana when it has to do with the therapeutic benefits," says Brad Burge, spokesman for the California-based Multidisciplinary Association for Psychedelic Studies, a longstanding scientific-research organization that studies such drugs as marijuana, LSD, and ecstasy.

Despite the scarcity of conclusive studies, doctors and researchers — including critics — agree that marijuana, or at least its constituent compounds, have positive uses in medicine.

Ailments that scientific studies and anecdotal reports say can be treated by marijuana products include pain from various causes including cancer, nausea (often related to cancer or AIDS therapies), multiple sclerosis, Parkinson's and Alzheimer's diseases, anxiety, depression, schizophrenia, post-traumatic-stress disorder, glaucoma, autism, hepatitis, wasting syndrome, Crohn's disease, and seizures.

"I see patients every week who talk about the benefits," says Tucson M.D. and clinician Margaret Gedde. "The big news is that [marijuana] is so tremendously helpful."

Even as the federal government insists through its drug policy that pot has no medical use, a major drug company, GW Pharma, sells the pot-based Sativex drug in countries including Canada and New Zealand to treat patients with cancer, multiple sclerosis, neuropathic pain, and arthritis.

Marinol, the brand name for a type of synthetic THC, has been used for years in the United States and actually is recommended as an alternative to pot by the U.S. Drug Enforcement Administration, when the DEA argues against any need for pot legalization. But, for many patients, Marinol isn't as good as the real thing.

Whatever new drugs scientists come up with based on marijuana, the fact remains that smoking or otherwise ingesting marijuana produces the same benefits as Marinol and Sativex. The American Medical Association's Council on Science and Public Health wrote in a 2009 paper that:

"Results of short-term controlled trials indicate that smoked cannabis reduces neuropathic pain, improves appetite and caloric intake — especially in patients with reduced muscle mass — and may relieve spasticity and pain in patients with multiple sclerosis."

There is no question that most doctors will say smoking anything is bad for the lungs. Pot smoke contains known carcinogens, such as benzene and formaldehyde, and common sense dictates that it can't be good to inhale smoke from burning embers, which includes hot tar and a potpourri of chemicals.

Yet even the notion that smoking pot is bad has been debated. Earlier this year, a major study out of the University of California-San Francisco found slight improvements in the lung function of marijuana users after years of moderate smoking.

Viewed from the rosiest of perspectives, then, marijuana comes off as a super plant.

Pot works as medicine because it taps into a special network in the body that has become a major area of scientific research.

In the 1960s, scientists trying to find the psychoactive components of marijuana isolated THC. It was the main chemical of several similar compounds in pot dubbed cannabinoids, after the scientific name for marijuana, cannabis. And it's the chemical most responsible for the high that users feel.

Then came a stunning find in the '80s: Our bodies are programmed to produce and use molecules that are similar to cannabinoids.

Researchers discovered that the human body contains many parking lots for cannabinoid molecules. When cannabinoids slip into these unique spots, they act as brain-message transmitters to help control appetite, responses to pleasure, the immune system, and much more.

This network became known as the endocannabinoid system ("endo" meaning within the body). Naturally occurring cannabinoids typically fill these gaps when appropriate. But flooding them with external molecules — which is what happens when marijuana is ingested — also triggers a response.

The high that users feel is one effect, a negative to those who want to isolate medical benefits. Other responses include release of anti-inflammatory and cell-protective agents, and the reduction of nerve pain.

The second major type of cannabinoid in pot is cannabidiol, also known as CBD — the stuff Craig Rodgers hopes will keep his cancer cells from reproducing.

Dozens of other cannabinoids also are released into the body after marijuana is ingested, and these are believed to work together to produce therapeutic effects. As recently as 2009, scientists discovered new cannabinoids in marijuana, boosting the number to more than 80.

In 2006, it was discovered that chocolate contains certain cannabinoids, too.

Much of the research into the endocannabinoid system has unfolded in the past 10 to 15 years, says Daniele Piomelli, a pharmacology professor at the University of California-Irvine and one of the foremost researchers on the subject.

Cannabinoids seem to work very well for certain conditions, but "we don't know exactly how this works," Piomelli says.

One of the most exciting areas of research into pot-based drugs, he says, is treatment of neuropathic pain, a "terrible condition" caused by nerve damage that often isn't relieved by traditional painkillers.

Piomelli says cannabinoids have been shown to be good as anti-anxiety, anti-psychotic, and anti-inflammatory agents. And the "data are very clear," he says, that the active ingredients in pot work for people suffering from nausea and lack of appetite: "It would be silly to deny that."

Cannabinoid receptors have been found throughout the human body — a few years ago, researchers located such receptors in the eyes. This seems to explain why cannabinoids like CBD and THC cause a drop in eye pressure, providing therapeutic relief to patients with glaucoma, which can advance to blindness. And that goes for whether the cannabinoids are inhaled or ingested some other way, according to a recent lecture by Melanie Kelly, a scientist with Dalhousie University in Canada.

Kelly, one of several healthcare experts who spoke on April 27 and 28 at the POT (Patients Out of Time) conference in Tucson, says her lab is trying to harness the effects of cannabinoids on the eye to develop better treatments for glaucoma and diseases that cause eye inflammation.

In its crude form, marijuana produces beneficial effects on eye pressure for only four to five hours, meaning it's not the perfect drug for glaucoma, Kelly says. Her goal is to find something so patients aren't "dosing all the time."

For many patients, of course, frequent "dosing" of marijuana isn't considered a problem.

The late-April POT conference at Loew's Ventana Canyon Resort brought together medical professionals, would-be pot-related business owners, and herb-possessing patients, the latter occasionally sneaking into the chaparral for quick tokes.

People at booths set up in a meeting room handed out educational pamphlets and promoted such products and services as a medical-pot-locating site, a company that tests bud for pesticides and other impurities, caregiver clubs, and hemp-based skin cream.

In one booth was Sandee Burbank, an elderly woman with white hair and a gentle face who looks like a character from a 1950s sitcom. She holds out a jar containing an ointment made from cannabis, olive oil, and beeswax. It works wonders for muscle pain, she claims, letting interested passersby take a whiff of it.

"It works quicker than ibuprofen," she says. "It relaxes your body but leaves your mind clear."

Hundreds of people filled the resort's ballroom for two days of lectures, though it wasn't obvious what many of the non-scientists were getting out of the presentations, some of which were highly technical.

Speaking a few days after the event, Arizona Department of Health Services Director Will Humble says, "It was unlike any academic conference I've been to in my 25-year career."

Humble, who attended the second day of lectures, adds that he realizes it wasn't meant to be a purely academic event. But what he found most striking was the enthusiasm for what is being promoted, ostensibly, as a medicine. In typical conferences dealing with scientific research, he says, observers are skeptical and presenters "are very careful not to overstate their conclusions or they'll get eaten alive by the audience."

At the POT conference, Humble says, the opposite sometimes was true.

It was easy to see what he meant. After Melanie Kelly's lecture, which drew no questions from the audience, two longtime pot smokers who have battled glaucoma stepped up to the lectern and stirred the crowd to applause several times.

Small, elderly Elvy Muskika of Oregon drew cheers as she told of the "freedom" she felt to speak her mind after her children went away to college and authorities couldn't take them from her.

"The mouth opened, and it hasn't closed since," she shouted. She then told the incredible story of three of her friends who were "terminal" at certain points, but thanks to their use of marijuana, "they are now cancer-free."

Of all the claims made by proponents of pot as medicine, the idea that marijuana can "cure" cancer is the most outlandish. Sure, as mentioned, some scientific studies show that THC and CBD can shrink tumors and kill cancer cells. But overselling pot can be dangerous to patients who might put off proven treatments such as chemotherapy or surgery.

One of the major promoters of pot as a cancer-killer is Bob Melamede, a professor of biology at the University of Colorado and CEO of a penny-stock company called Cannabis Science. On the company's website are four case studies that include graphic photos of supposed skin-cancer lesions healing over time. Without credible supporting documentation (one case study includes two doctors' letters with the alleged physicians' names removed), the photos prove nothing. Melamede admits that one of the case studies includes photos that were submitted by the patient.

Melamede, wearing glasses and casual clothes at the conference, likes to be called "Dr. Bob." He's given treatment advice to patients, including Craig Rodgers, though he holds a Ph.D in molecular biology and biochemistry, not a medical degree.

During an interview before his conference lecture, Melamede discusses his ideas with New Times and several other people who have stopped at his table.

"It's all about how flowing energy directs the organization of matter," Melamede states, ending the sentence with an expectant stare, as if he wants to see a listener's mind blown by the idea. He confesses that he has attention-deficit disorder and "jumps around a lot."

Dr. Bob insists that the skin-cancer stories are true.

"With seeds and some dirt, you can produce medicine to cure your cancer," he says, noting that his company plans to open a Mesa clinic in coming weeks.

A hulking senior citizen at the table with Melamede, in response to New Times' skepticism, points to his leg, arm, and chest as he explains how pot oil got rid of his own skin cancer.

Melamede's new branding and licensing director, Andrew Pitsicalis, who says he previously worked in merchandising with Leon Hendrix, one of Jimi Hendrix's surviving brothers, mentions that the large senior citizen is famous — he's Robert Platshorn, a former marijuana smuggler who spent 30 years in prison before writing a book about his experiences.

Pitsicalis doesn't seem to understand that this information makes Platshorn's testimonial less credible.

Jacqueline Spruce, an Australian businesswoman with a booth at the conference, doesn't come across as kooky as Platshorn. Yet one of Melamede's four case studies includes pictures of Spruce's nose and a lesion that once was on it. She and partners hope to open a cannabis-based medical clinic in her country, if authorities allow it. One of the first medicines they want to offer is a pot cream for skin cancer, she says.

"I can't be skeptical," she says. "It cured my cancer."

More believable than such contentions is the idea that marijuana is an effective and relatively safe palliative medicine. That is, it may not cure certain serious conditions, but it does make patients feel better.

Phoenix's Paul O'Connor, 59, is one of thousands of state residents who says he uses marijuana to control his chronic pain.

"My back injury causes spasms in my spine," O'Connor says. "It radiates over my hips into my groin. The marijuana, it takes the edge off that. And it keeps me from having to ingest other chemicals, like muscle relaxants."

Another registered marijuana patient, Jean Matherly, also says she uses pot for back pain because of degenerative disk disease.

"Marijuana reduces the stress, and it relaxes the muscles," she says. "I can pretty much sleep all night with it."

There's no reason to think marijuana isn't helping these patients. But they both began using it long before they were injured. Matherly, who says she's smoked pot on and off since the 1970s, admits she probably would smoke it even if she didn't have chronic pain.

Many, perhaps most, registered patients in Arizona don't have conditions much more serious than Matherly's or O'Connor's. The latest stats show that 4 percent of the state's 28,289 registered marijuana patients have cancer. A mere 1.72 percent of patients, or 492 people, have glaucoma.

Chronic pain, however, was listed as a condition by 89 percent of patients. Pain often is a purely subjective concept, leading critics to call the qualifying ailment of "chronic and severe pain" a loophole for recreational users.

Chronic pain is a common condition suffered by about a third of Americans. Therefore, it's likely many of Arizona's licensed users do, indeed, have such pain. But the notion of medicinal use becomes less clear when users also happen to enjoy the buzz they get from their medicine.

With pot now legal for these users, the question turns back to safety. And there's no question that pot itself has minimal toxicity.

Representatives of Valley poison-control centers contacted by New Times say the first question healthcare professionals ask when a patient has an extreme reaction to marijuana is whether the weed was tainted with something dangerous.

Keith Boesen, managing director of the Arizona Poison and Drug Information Center, reports that of 65,000 phone calls to the center in 2010, 26 concerned marijuana. The center received calls from a woman who said, after trying pot for the first time on her birthday, that her "lungs were burning." Another case involved a 13-year-old boy whose father took him to an emergency room because he was acting disoriented and confused. Another was a 1-year-old who "presumably ate something."

Boesen says, "[The baby] was very altered — wasn't all there, very drowsy. What's tricky in kids — they have different tolerances than adults do in many cases."

In general, though, people can overdose on just about anything, including water, Boesen notes.

"On the spectrum of toxins, marijuana is not one . . . we're concerned about," he says. "In the event someone has a significant problem, the first thing [healthcare workers] think is that it wasn't marijuana."

Still, pot is not totally without risk. Though rare, it's possible that marijuana could trigger a latent psychotic or schizophrenic episode. Dr. Eric Voth, an anti-pot crusader who's chairman of the Institute on Global Drug Policy, says he's treated several patients who "smoked no more than three times and become psychotic for several years."

People with psychosis, he says, may have hallucinations, extreme paranoia, or exhibit irrational behavior.

On the other side of the aisle is Dr. Sue Sisley, an Arizona doctor hoping to persuade the federal government to let her conduct clinical studies with marijuana on people with PTSD. In her proposal, Sisley outlined the safety measures she plans — mainly having staff members on hand to watch for problems — in case users in a trial "get a psychotic break or a panic attack."

Such immediate problems subside quickly, she says, and the patient usually feels better the next day. But there are cases of people exposed to cannabis in their teens who "go on to develop full-blown schizophrenia," she acknowledges.

With uncertainties remaining about whether pot can cause mental illness in rare cases or whether mental illness causes certain individuals to seek out pot and other mood-altering substances, it's only prudent, Sisley says, to test marijuana on people 21 or older.

Despite the small risks inherent in the study, Sisley expects that if she gets the go-ahead, she'll have an abundance of volunteers.

One aspect of medical pot that can't be overlooked is the primary side effect: being stoned. Dr. Gedde, the Tucson doctor who recommends marijuana for many different ailments, says the high — while delivering part of pot's palliative benefit — also is one of its drawbacks.

"It wouldn't help your sharpness in a lecture," she says drily. Gedde says novice medical users she treats "feel they're not quite there, not in control."

Gedde suggests that medical-marijuana patients avoid smoking and use a vaporizer.

However, a 1996 study sponsored by the National Organization for the Reform of Marijuana Laws and the Multidisciplinary Association for Psychedelic Studies proved that vaporizers still allow plenty of tar to enter the lungs, while filtering out much of the THC. The study concluded that no matter how pot is inhaled, using the highest-potency marijuana available is best because less pot must be consumed for the desired effect.

As a main focus of her hoped-for study, Sisley wants to compare the therapeutic effects of pot ingested with vaporizers to those of marijuana ingested by smoking.

"Marijuana seems to reduce nightmares and improve sleep in a dose-dependent manner," she says. "The thinking is, how do I prescribe this in a way that makes sense?"

Long-term use of marijuana would be counterproductive if it makes a patient sicker. But Sisley says respiratory or other possible pitfalls of heavy or daily use have to be weighed against apparent benefits.

"I have found medical marijuana tremendously helps with my severe PTSD," a combat veteran wrote to the state in January in an attempt to persuade the Department of Human Services to add his condition to the list of qualifying ailments.

The man, whose name was redacted in documents, says staff at the U.S. Veteran's Administration "highly advocated" pot as a viable treatment option for him after 12 different medicines, including morphine, incapacitated him without any positive results for about three years.

Now, the veteran writes that he is more clearheaded, happier, and "less of an angry person with less aggression."

Which can't be a bad thing.

Ray Stern is a staff writer for the Phoenix New Times, where this story was originally published.