Hillary Clinton has had a "serious concussion," falls, double vision and other health episodes, causing great concern for her physical health – and now it's been revealed that one of her top aides extensively researched a drug used to treat Parkinson's and Alzheimer's diseases.

While he worked for her at the State Department, Clinton Deputy Chief of Staff Jake Sullivan investigated the drug Provigil, according to an October 2011 emails sent to Clinton.

In one email, Sullivan tells Clinton the military administers Provigil, a drug that's also used to treat narcolepsy and sleep-wake disorders.

"Provigil is used to treat excessive sleepiness caused by narcolepsy or shift work sleep disorder (sleepiness during scheduled waking hours among people who work at night or on rotating shifts)," Sullivan wrote in a prior email, according to the Daily Caller.

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He said doctors often prescribe Provigil to treat "excessive sleepiness in patients with Parkinson's, Alzheimer's and multiple sclerosis."

Sullivan further explained that Modafinil, a generic name for the drug, "gained attention in the medical community because it is the first effective stimulant with no significant potential for abuse" and "it can be used for two to three day stretches at a time, with few known side effects and little risk of addiction."

One of Sullivan's emails to Clinton:

If the latest headlines are any indicator, many Americans appear to have questions about the health of the woman who could be America's next president.

According to CNN, if you do have those questions, you’re a "conspiracy theorist." And a "healther."

On Tuesday, CNN launched a defense of Clinton in light of the many questions that have been raised simply by her appearance, her behavior and her actions.

But never mind whether the progressives lash out with a label, because there's a troupe out in Hollywood making sure she knows the fastest way to the hospital, putting "Hillary" signs next to all the local directions to hospitals.

The Gateway Pundit posted some of the images.

CNN, meanwhile, posed a long list of questions about Donald Trump's health, poking fun at a doctor's report that said he is strong and has a high level of stamina.

Then the network took off on a tangent, labeling those with questions about Clinton "healthers."

CNN said they "are using junk science and conspiracy theories to argue that Clinton is suffering from a series of debilitating brain injuries."

"There is absolutely no credible evidence to backstop any of these claims," CNN claimed.

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Just one day earlier, amid increasing speculation about her health, Clinton sought to reassure voters in an appearance on "Jimmy Kimmel Live," opening a jar of pickles and telling the host, "Take my pulse … make sure I'm alive."

Questions have been raised about her health for years, with reports of a concussion, fainting, falling, uncontrolled coughing, blood clots, six-month recovery periods and episodes of losing focus. The speculation surged during her campaign for the Democratic Party nomination and has only increased since her party's convention.

She has admitted to suffering a "serious concussion," and husband Bill Clinton once spoke of a six-month recovery period after a health episode.

On Monday, she was on comedian Jimmy Kimmel's television show joking about the very serious issue of the health of a woman who would be president.

It was a reprieve, however, from the new evidence that the Clinton Foundation was a "pay-for-play" operation that gave donors access to the State Department while she was secretary of state.

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On the Kimmel show, Clinton said, "Take my pulse, while I'm talking to you – make sure I'm alive."

Kimmel quipped, "Oh my God, there's nothing there!"

The host also had her open a jar of pickles to prove "she's not on death's door."

Former New York Mayor Rudy Giuliani, however, doubled down on his worries about her health.

"I think Hillary is tired. I do," Giuliani said in an interview on "Fox and Friends" Monday. "When I saw Hillary at the press conference sitting down with a Hillary supporting police chief pretending she is pro-police. It is one of the most pathetic press conferences I've ever seen. Well, first of all, she looks sick. Number two, she looks completely uncomfortable saying anything pro-police."

And another prominent doctor expressed concern. Bob Lahita, a professor of medicine at Rutgers, told Fox Business, "The very fact that she's having these [blood] clots and she's had two bouts of thrombosis is disconcerting to say the least.

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"You go back to the history of our presidents and we've had many presidents up until Lyndon Johnson who’ve concealed their health during their campaigns, and it had dire effects for our country, going from Kennedy to Roosevelt, to Woodrow Wilson whose wife ran the White House for some time – so we have issues here and I think both candidates should be very forthcoming and perhaps have an impartial panel of physicians review the data and make that kind of decision before Americans go to the polls," remarked Lahita.

And it was revealed that several years ago, at a time when Clinton suffered a concussion, her adviser Philippe Reines contacted the NFL for information about severe head injuries.

Later, Clinton thanked Reines for his help, stating, "Having a cracked head is no fun at all."

A tech writer for the New York Times has called on Google to hide evidence of Clinton's "failing health."

That was after Giuliani said "all you gotta do is go online" to find out she is not well.

Meanwhile, the Drudge Report on Monday highlighted a less-than-flattering image of Clinton with the headline "Excellent Health."

The Clinton campaign hasn't addressed her health with documentation since 2015 when it released a statement from internist Lisa Bardack concluding she was in good health.

It was Breitbart News that reported New York Times tech columnist Farhad Manjoo wants Google to hide the evidence.

"Google should fix this. It shouldn't give quarter to conspiracy theories," he wrote.

Only a couple days earlier, the Clinton campaign lashed out at the publication of videos and the images suggesting she is unwell, calling the reports "deranged conspiracy theories."

Dr. Jane Orient of the American Association of Physicians and Surgeons had bluntly asked, "Is Hillary Clinton medically unfit to serve?" She has recommended a thorough independent assessment of Clinton's health.

And a video shows many others are raising similar questions.

WND has reported a wide range of concern over Clinton's health.

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Television doctor Dr. Drew Pinsky, for example, was on KABC's "McIntyre in the Morning" radio show to discuss Clinton's medical records.

He and another physician found reason for "concern."

"Both of us concluded that if we were providing the care she was receiving, we would be ashamed to show up in a doctor's lounge," Drew told the show's hosts. "We would be laughed out. She's receiving sort of 1950s-level care by our evaluation."

Gerard Gianoli, M.D., a member of the American Association of Physicians and Surgeons, or AAPS, argued that if the concerns were about Donald Trump's health, establishment media would spotlight the issue.

He wrote:

Imagine, if you would, that tomorrow Donald Trump suffers a concussion. Suppose he trips on a flight of stairs, falling down and hitting his head. The head injury is so severe that he is unconscious for a time and has to be hospitalized for a week. After getting out of the hospital, the Trump campaign tells us that he has fully recovered and that there are no lingering effects of the head trauma. During the following weeks, he is seen in public to wear glasses with a Fresnel lens on one side. He also seems to have trouble maintaining his balance, loses his thoughts in the middle of speeches, and has episodes of spasmodic movements suggestive of seizures. In this imaginary scenario, would it surprise anyone if the media became skeptical and pressed for release of Mr. Trump's medical records? Would it surprise anyone if the Clinton campaign made an issue of Mr. Trump’s health status during speeches and in TV ads? Would the media cry 'foul' over the Clinton campaign doing so? I think the answers to these questions are self-evident. The media and the Clinton campaign would be all over this like white on rice, and no one would question the appropriateness of their actions. To my knowledge, Mr. Trump has had no such issues with his health. However, Mrs. Clinton has had multiple problems – some she has revealed and some that she has not revealed.

Gianoli, in private practice in Covington, Louisiana, and a faculty member at Tulane University School of Medicine, has pioneered treatments in his specialty areas. He has been granted the American Academy of Otolaryngology's Honor Award, among others.

Gianoli was pointed in asking: "What do we know about Mrs. Clinton’s health? We know that she has suffered two deep vein thromboses and an episode of cerebral venous thrombosis. Blood spontaneously clotting within one’s veins on three separate occasions is not a good thing. In fact, it is life-threatening. This tells us that she has a hypercoagulable state requiring the use of Coumadin (a 'blood thinner') for the rest of her life to try to prevent this from happening again. While Coumadin may prevent future blood clots, it can also lead to life-threatening hemorrhage if she has any future trauma."

He added: "We also know that she suffered a concussion and, according to her husband, she took 6 months to recover. How do we know she recovered? If she was a high school athlete, she would have had mandatory neuropsychological testing before being allowed to participate in sports again. Given that being the leader of the free world is more important than playing goalie for the local high school, why is the mainstream media not demanding to see Mrs. Clinton’s post-concussion testing?"

He noted her own supporters have talked about her "right transverse venous sinus thrombosis … a blood clot that formed in one of the two major veins that drain blood from the brain."

The symptoms are "headaches, visual problems, and dizziness/balance problems."

"We know that Ms. Clinton has had all three of these. Less commonly known are 'brain fog,' problems with concentration, and short-term memory problems. Sounds familiar?" he questioned.

Orient said the evidence is there for people to review.

"There's the photograph of Secretary Clinton's difficulty walking up some steps. Now inability to climb stairs does not necessarily disqualify a person for public office. However, neither she nor people with her apparently anticipated a problem. The people helping her seem to be preventing a fall. Did she simply trip? Or was it a seizure or a stroke?

"Videos widely circulated on the Internet are, if authentic, very concerning. One shows prolonged, inappropriate laughter; another, strange head movements. In a third, she appeared momentarily dazed and confused, and lost her train of thought. Reportedly, she has a volcanic temper. (This is probably not new)," Orient wrote.

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The incident in which Clinton needed help going up stairs happened during a February event in South Carolina.

There also have been videos that have raised questions.

One appears to show her losing her concentration while speaking.

She simply comes to a halt and stares at the audience.

See the video:

And a July 21 video posted on YouTube shows Clinton's head suddenly turning and shaking vigorously for several seconds.

Blogger Jim Hoft of the Gateway Pundit headlined it, "Wow!" Did Hillary Clinton Just Suffer a Seizure on Camera?"

"The poor woman is in worse shape than we thought," he wrote.

Fox News medical "A-Team" also raised questions.

Dr. Marc Siegel noted: "In 2008 … I looked over a thousand pages of John McCain's records because of a melanoma he had 10 years ago. What about Hillary? In 2009, a severe fall. She breaks her elbow. In 2011, she boards a plane, falls. In 2012, she has a severe concussion which Bill Clinton says took her six months to recover from."

He continued: "Then she ends up with a blood clot in the brain and a lifetime of blood thinners. Just that point alone – if she's prone to falling, you can see from that picture up there that it looked like she can barely get upstairs without two people carrying her. Guess what if she falls and hits her head? She'll get a blood clot."

And Dr. David Samadi added: "The picture going up the stairs speaks a million words. Is she fatigued? Is she dehydrated? One of the main reasons she fell in 2012 and had the concussions was severe dehydration. They're holding her and going up the stairs. So she may be really dehydrated, she may have arthritis, she may have back pain, she may have fallen again. We don't know."