However, therapy is a treatment of the willing, and if he is unwilling, even if you convince, cajole or otherwise twist his arm to get him along to an appointment, then therapy is unlikely to have much impact.
In many ways, this is the paradox of therapy for depression, especially the kind of long-standing mood problems you describe with your son. Depression shapes how we think, and over time those thought patterns can become habits - with depression less being something that comes and goes, and more something that is a pervasive outlook - what some people might even consider part of the personality.
But this doesn't mean it can't change.
So if you are to encourage him towards some kind of treatment, then initially it's important to keep expectations low - to simply support him to find someone he may want to try talking to, and to commit to it for a period of time, probably at least six months.
It can be tempting to try to see therapy as the silver bullet and to want to sell it to him, but paradoxically trying to build hope in this way can actually set the therapy up to fail, and further reinforce his hopeless and cynical view.
What's also important is how you manage your own expectations and responses to your son - a hard task, because as a parent it's heartbreaking to see our children suffering, regardless of their age.
The challenge for close whānau with the "horse to water problem" is to recognise and accept the limits of the help we can actually provide.
My challenge to you is to recognise the problem that trying too hard to help can cause, namely resistance.
It's natural for all of us to feel defensive or even push back when we feel we're trying to be convinced of something and this can be counter-productive, in this instance decreasing the chances of your son engaging in help.
Successfully helping then requires a careful balance of offering information, empathising with the difficulties he faces (even if you can see that he may not do things to help himself) and reminding him that help is available.
So, be clear about what help you're prepared to offer, whether that be helping to find treatment, financial support for therapy, going to the doctor with him, or taking him to counselling appointments.
But offer it gently - lay it on the table as it were - and leave it there.
And this is a challenge of acceptance. To accept the limits of what we can do, and recognise what will work, what won't work, and your son's need - right even - to choose.
Because he has a right to choose, even to make bad choices, and he needs to take responsibility for those choices. And you have the right to look after yourself and accept that you may have already done all that you can.
Letting go is hard, but trying to change someone who doesn't want to change - or isn't ready to yet - is harder, and in the end, only harms us, and the relationship we have with them.
Looking for support? It's available
• Call or text 1737 any time for support from a trained counsellor
• Call PlunketLine 24/7 on 0800 933 922
• Depression helpline: Freephone 0800 111 757
• Healthline: 0800 611 116 (available 24 hours, 7 days a week and free to callers throughout New Zealand, including from a mobile phone)
• Lifeline: 0800 543 35
• Samaritans: 0800 726 666
