A "horrible trauma" might have triggered such an outburst, according to McCann. But typically flashbacks only last 10 to 15 minutes, she said, not the extended length of time Osbon was reported to have been forcibly subdued.
"If you had just the right circumstances -- no sleep, taking stimulants and a history with a PTSD trigger, he could have had weird flashbacks."
Another suspicious element is that Osbon was reported to have had visual hallucinations during the incident, which are not typical in psychotic breakdowns. Those with schizophrenia more typically have auditory flashbacks and "mental thoughts," according to McCann.
"It sounded like he was seeing things, and that is highly suggestive of an encephalitic event or a brain tumor," she said.
McCann applauded how passengers and crew handled Osbon's outburst. "Those were not ideal circumstances and they were brilliant," she said.
The "hero" passenger -- David Gonzalez -- said he was sitting in the second row of the plane when Osbon stormed out of the cockpit and rushed toward an occupied bathroom.
Flight attendants struggled to control him and Gonzalez, a 50-year-old from Pennsylvania on his way to a security convention, stopped the pilot as he moved in the direction of the plane's emergency exit.
Gonzalez put pressure on Osbon's windpipe and threw him to the floor where he sat on the pilot until the plane safely landed.
Anxiety psychologist Dr. Gregory Jantz, author of the 2012 book, "Overcoming Anxiety, Worry and Fear," said panic is a perfectly plausible in this scenario, especially in this age of terrorism.
Fear of flying is now number three among the top 10 phobias, according to Jantz.
"It has all the characteristics of a common panic attack and we are seeing more and more in our work with celebrities and sports figures and high-profile individuals," said Jantz.
"Professionals are more prone to panic attacks," he said. "One, they are high-performers. If you are a pilot or an athlete, you may be dealing with an underlying anxiety. Eventually, the body says, 'I can't carry this any longer.'"
Two to 5 percent of those who have panic attacks "do step over and lose touch with reality," according to Jantz.
He said the pilot may have had an anxiety disorder for some time.
"And usually, they find ways to self-medicate," said Jantz. "They look for ways to calm themselves and unfortunately, it can be self-destructive."
Fatigue can also trigger a panic attack, he said. "That is very common. People with anxiety disorder tend not to get enough REM sleep and they are in constant fatigue. That adds to the anxiety and can be a ticking time bomb."
Without treatment, panic disorder can get worse and sufferers can be "paralyzed by fear," he said.
But McCann said she believes that an underlying medical condition may explain Osbon's out-of-control behavior.
"If it's one of those toxic-induced things, we will know soon," she said. "I am hopeful for the pilot that it's the cause, because of his lack of prior history and there were no red flags in his exams."
"But if everything is negative and he continues this behavior in a very psychotic way," she said. "That will be a problem."
ABC's Matt Hosford and Christina Ng contributed to this report.