'Growing up, whether it be having a single parent, trying to deal with that at a young age, not knowing how to deal with it, [were] among a lot of other things [that caused stress for me]... it was learning how to deal with these issues,' he continued.
The actor also admitted that initially he was wary of seeking help.
'Initially, for me personally I'm somewhat proud, like you know, 'I don't have a problem,' that sort of stuff, that bravado... but it slowly creeps up on you. You find yourself being quite depressed.'
Over the past 10 years or more - discounting the last 12 to 18 months because obviously I've been very preoccupied with my brain cancer over that time - there have been many times I've been down,' he confessed to The Daily Telegraph on Saturday.
'I had thoughts 'what if I wasn't here anymore' and 'what's the point of being here', things like that,' he went on.
The interview was also the first time Johnny has spoken openly about the domestic violence that he and his older brother witnessed his mother suffer at the hands of a former partner.
Last year Johnny shocked fans by revealing he’d had a 7cm tumour removed from his skull and was currently undergoing chemotherapy for a brain tumour.
This article originally appeared on WHO.