Casey has also lost his brother-in-law and two other friends to suicide.
"It's definitely a thing of sometimes you don't see it coming because guys like to hide things as much as they can.
"[Mental illness] is one of those things where you think you have to sometimes keep it in, or you might come across soft or you might come across a bit more needy than what you need to be."
Casey told the Herald on Sunday the loss of so many of his loved ones has made him realise not only the lasting impact suicide has on family and friends but just how many Kiwis are taking their own lives.
Provisional figures released last month show 606 Kiwis committed suicide between July last year and this June. When it comes to gender, for every woman that dies by suicide, three men do.
The Herald ran a special series on youth suicide this year called Break The Silence, which was aimed at starting a national conversation about the issue.
"Doing some simple things could make big problems not become as big and hopefully bring down the number of people getting to the point of committing suicide," Casey told the Herald on Sunday.
The pair don't claim to be experts on suicide prevention, but say they are speaking as friends who want to be there if a mate is suffering from mental illness and help others do the same.
"It's alright to not be alright," said Casey.
Pryor emphasised the importance of not feeling too awkward to raise the topic with a mate you are worried about.
"It's just a conversation. It really is not a big deal as soon as you start talking about this stuff."
Pryor said it was better to be wrong than be silent. He also encouraged people suffering from mental illness to speak up and ask for help.
"The big thing is, if they're your friend, they're certainly not going to judge you if you are dealing with mental health issues."
If a friend tells you they are not okay, the pair said it was important to remember that you don't have to try and fix the problem alone. Talk among your mates and come up with a plan, whether it is telling them to see a professional, sending them a text or catching up more often, they said.
"That little boost can just really help someone's day," said Casey.
Mental Health Foundation chief executive Shaun Robinson, who lives with bipolar, said whenever he feels depressed and anxious, he gets a message in his head that he is weak, people will judge him and that he has to be the tough male and not say anything.
"That conditioning on us blokes is really strong and the self-stigma about scary thoughts and feelings runs deep," he said.
"But every time I do open up and tell people I'm not feeling so good it's a huge relief; it helps me to recover more quickly, I get kindness and support from heaps of people and I'm blown away at how many other blokes from all walks of life tell me about their experiences.
"That's when I realise that opening up is a big part of being a good bloke."
Where to get help:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
Or if you need to talk to someone else:
• LIFELINE: 0800 543 354 (available 24/7)
• SUICIDE CRISIS HELPLINE: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• YOUTHLINE: 0800 376 633
• NEED TO TALK? Free call or text 1737 (available 24/7)
• KIDSLINE: 0800 543 754 (available 24/7)
• WHATSUP: 0800 942 8787 (1pm to 11pm)
• DEPRESSION HELPLINE: 0800 111 757
