Speaking to the Sunday Times Magazine, Young spoke about having the anxiety disorder and addressed Morgan's claim that he instead had "whiny, needy twerp syndrome".
Morgan, who received a backlash after disputing Young's mental health experiences on social media, had added: "Seriously, is there any celebrity left in the world not currently suffering from PTSD?"
He described the term as "massively overused" and claimed it "damaged focus for those with real issues".
Young was angered by Morgan's response although admitted he was initially "terrified" when he saw the TV host at the CHelsea Flower Show. "Then I was like, I'm not letting that s**tbag walk away without telling him".
Young claims to have approached Morgan with his mother. The journalist comments that it sounded as though the pair had "a right old English barney, trying to explain the definition of trauma, refusing to shake each other's hands and so on... Bill Bailey was on the sidelines, telling them to move on".
Morgan told Young his brother had served in "actual wars" while Young replied that both his grandfathers had PTSD. The singer then turned to Morgan's parents.
"I said, 'I'm so sorry your son has turned out the way he has, because you both seem like really nice people', and I grabbed my mum's hand and sashayed into the flower show."
Young revealed he has PTSD after pulling out of the 2016 series of Strictly Come Dancing.
"I was really ill," he told Bryony Gordon's Mad World podcast. "I was dragging myself to rehearsals. I couldn't do it anymore."
His new album Lexicon is released on 14 June.
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