Lord Sutch fought long battle with depression.
The 58-year-old founder of the Monster Raving Loony party was "a comedian with tragedy at his heart", said Hornsey coroner Dr William Dolman.
The rock and roll musician was found hanging on the stairs at his late mother's home in South Harrow, north-west London by his fiancee, Ms Yvonne Elwood, on June 16.
Dr Dolman said: "He clearly was a man who had suffered from depression for a long period." He added: "The public saw the public face, a cheery, outgoing character, yet in the privacy of his room, his true character, his true sadness, appeared."
Dr Dolman added: "I suppose in a sense his life is a tragicomedy. It has come to a sudden end, an end he had obviously planned.
"The entertainment and fun he brought to many people in what one might call the sometimes unsavoury world of politics, I hope, will be remembered longer than the events of June this year.
"I record that David Sutch killed himself, and I'm going to add, while suffering from a depressive illness."
Ms Elwood, Lord Sutch's fiancee, of Elgar Road, Reading, told the inquest that Lord Sutch had been taking tablets for depression for quite a long period when she first met him.
"He suffered from manic depression for many years," she said.
"He had a public face, and a private face, which was, most of the time, severely depressed."
She added: "It would affect him physically, his whole face would drop, and he just couldn't cope."
She last saw him on Sunday June 13, at around midnight. After failing to contact him on Monday and Tuesday, she went to the house in South Harrow on the Wednesday. "He was on the stairs. He looked as if he was just leaning on the banisters."
Former madam Ms Cynthia Payne told the inquest that she had become friendly with Lord Sutch because they shared an election agent and he had lived at her house from 1988 to 1991.
Ms Payne, aged 66, who described herself as an after dinner guest speaker, said: "He was like a little boy, he always called me 'Mumsy'.
"He never slept properly, he used to get up at three in the morning.
"There was one occasion he woke up and was screaming coming down the stairs with a nightmare.
Ms Payne said the death of Sutch's mother had a bad effect on him.