Viewers have seen this week's tram crash trigger the disorder as Gary suffered from flashbacks to his recent experiences in the army.
"His recovery is going to be a slow process," North told What's On TV. "He's really quite mentally ill now. It's heavy stuff and we'll follow him as he tries to cope with what he's going through."
North admitted that nothing Gary's parents Anna and Eddie does can help him with the situation.
"Anna is pussyfooting around him, but Eddie is like, 'Get your arse out of bed and get yourself sorted'," he said. "But neither technique is working."
Confirming that he had spoken to real soldiers about their experiences, he added: "One guy told me that two years after he'd been in Afghanistan, a tyre blew in the street and he threw himself behind a wall. It triggered a flashback. Apparently that's quite common with post-traumatic stress disorder."
> Click here to read our recent interview with Mikey North