He had developed alcohol addiction in his teens and later admitted to a cocaine addiction. He did not seek therapy until he was 45.
King, 57, began the radio show The Nutters Club in 2009 - firstly on Radio Live then later on Newstalk ZB - which encouraged frank conversation about mental health issues. In 2012, he formed the Key to Life charitable trust.
A year later he began focusing on youth mental health, which has become his defining role.
He once said stand-up comedy wore him down because it was toxic and thrived on negativity. But he has applied his direct, confrontational approach from stand-up comedy also to his work in mental health.
He quit the Government's suicide prevention panel in 2017, calling it deeply flawed because it did not include a measurable goal for reducing suicides.
His energy instead went into a national roadshow called I Am Hope, in which he and other speakers travelled from Bluff to Cape Reinga last year to speak to 20,000 young people about positive solutions to a rising suicide rate in New Zealand.
King also created the Gumboot Friday initiative, which came from his description that having depression was like walking through mud each day. It raised nearly $1 million in April towards free counselling for young people.
Earlier this year, he was named Kiwibank New Zealander of the Year.