"I'm not saying anything other than pathological is a very serious disease. And he said he's pathological, somebody said he has pathological disease," Trump said.
"It's in the book that he's got a pathological temper," Trump continued. "That's a big problem because you don't cure that."
Trump then offered the example of a child molester.
"You don't cure these people. You don't cure a child molester. There's no cure for it. Pathological, there's no cure for that," he said.
When asked about Trump's comments by CNN, Carson adviser Armstrong Williams brushed off Trump's concern about the retired neurosurgeon's temper.
"Mr. Trump likes Dr. Carson, but Mr. Trump has resentment when he sees Dr. Carson rise," Williams told CNN. "He lashes out like he did tonight and resents Dr. Carson's continued rise and Dr. Carson (getting) the attention of the press and American people."
Fellow Republican presidential candidate Carly Fiorina also dismissed Trump's concerns while knocking his previous complaint that she kept interrupting other candidates during the Fox Business Network debate.
"Donald, sorry, I've got to interrupt again. You would know something about pathological. How was that meeting with Putin? Or Wharton? Or your self-funded campaign? Anyone can turn a multimillion dollar inheritance into more money, but all the money in the world won't make you as smart as Ben Carson," Fiorina wrote on Facebook Thursday night.
Watch Trump's interview on CNN: