President Trump denied recent claims questioning his mental stability while calling himself “really smart” and a “genius” in a series of tweets sent early Saturday morning.

“Now that Russian collusion, after one year of intense study, has proven to be a total hoax on the American public, the Democrats and their lapdogs, the Fake News Mainstream Media, are taking out the old Ronald Reagan playbook and screaming mental stability and intelligence.....” the president penned on Twitter.

In the tell-all book published Friday, Fire and Fury: Inside the Trump White House, Michael Wolff wrote that "100 percent" of people close to Trump with whom he spoke concluded Trump was "incapable of functioning in his job." That claim, along with a report earlier this week which revealed that lawmakers met with a psychiatrist to question the president’s mental health, led to days of discussion in the media and by pundits on the matter.

Trump followed up with another tweet explaining his "two greatest assets," his "mental stability and being, like, really smart" he said led to his 2016 election rival, Hillary Clinton, to go "down in flames."

"I went from VERY successful businessman, to top T.V. Star," Trump continued, adding “ President of the United States (on my first try). I think that would qualify as not smart, but genius....and a very stable genius at that!” Trump concluded.

Trump also mentioned Ronald Reagan, who before Trump was the oldest president. His critics often made suggestions that he had dementia, noting that he would contradict himself, forget names, or appear absent-minded. Six years after finishing his second term, Reagan announced he was diagnosed with Alzheimer's disease.

Doctors and key aides told Dr. Lawrence Altman, a New York Times reporter who interviewed Reagan about this health, that they didn't notice any changes to Reagan's mental ability while he was in office, but one study found Reagan's speech patterns exhibited some changes, like not using unique words. These signs, however, don't necessarily indicate that his judgement or decision-making was impacted.

White House press secretary Sarah Sanders largely avoided discussing her boss's mental health during the press briefing this week, instead telling reporters that the country should be more worried about North Korean dictator Kim Jong Un.

"It's disgraceful and laughable," Sanders said of criticism aimed at Trump's mental state during the press briefing on Thursday. "If he was unfit, he probably wouldn't be sitting there," she added.

Trump is scheduled to undergo a medical exam next week on Jan. 12, but critics are likely to be disappointed.

Trump is scheduled to undergo ​his first ​routine medical exam ​as president on ​Jan. 12 ​at Walter Reed National Military Medical Center, but an extensive mental health assessment isn't typically part of the exam.

​Still, some assessment may be included. Experts recommend people over age 65 are screened by a primary care provider on memory, function, depression, and anxiety. ​

No law demands disclosure of a president's medical record​ or that its details are complete​. As was the case under past presidents, a doctor will only release information the patient has consented to.