Country Victorian MP Russell Northe says his depression has been so bad at times he could not get out of bed and contemplated suicide.
Mr Northe quit the Nationals on Monday and will see out his term as the Member for Morwell as an independent MP while focusing on recovering from mental health and gambling issues.
"It all came to a head in more recent times where it simply got to the point where I couldn't get out of bed in the morning," Mr Northe told 3AW on Monday.
"I have to confess, I've been very close to not being here on a number of occasions."
Mr Northe said he had failed to discuss work and personal pressures which added to the problem.
During the past four years he lost a close friend to illness, a family member was battling drug addiction and a family business venture did not go as planned, he said.
Professional triggers included disastrous events in his electorate such as the Black Saturday bushfires, closure of Hazelwood power station, and being away from his family.
"A combination of all those things led me to probably overindulging in booze and gambling on occasion," he said.
He admitted he had "incurred some personal debt" as a result, but did not say how much.
He said he was leaving the Nationals with no animosity and that the team had been supportive.
Nationals leader Peter Walsh said the party had been supporting Mr Northe with his struggles for about a year, but was unaware of his plans to quit until a statement was released to the ABC earlier on Monday.
"Our core focus has been Russell's wellbeing and the wellbeing of his family," Mr Walsh told reporters.
The party has had little contact with Mr Northe since he went on paid leave from parliament in June, citing personal health reasons as he shut down social media and email accounts.
The Nationals will start a preselection process to look for a candidate ahead of the November 2018 election in a seat with a tight margin.
Member for Eastern Victoria Melina Bath will assume responsibility for the Latrobe Valley from her Traralgon office.
Premier Daniel Andrews told reporters on Monday he wished Mr Northe "all the very best and I hope he's getting the support he needs".
Australian readers seeking support and information about depression can contact Lifeline on 13 11 14.
Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.
Suicide Call Back Service 1300 659 467.
MensLine Australia 1300 78 99 78.