Pope Francis has revealed for the first time he sought help from a psychoanalyst 'to clarify a few things'.

In a new book Francis said he had weekly therapy sessions in his native Argentina at the age of 42 when he was leader of a Jesuit order under the country's military dictatorship.

Long before he was elected head of the Catholic church, when he was simply the Argentine Jesuit priest Father Jorge Mario Bergoglio, the now Pope said the regular appointments with the Jewish psychotherapist 'helped me a lot'.

Speaking to French sociologist Dominique Wolton for a new book, Pope Francis: Politics and Society, he said: 'At a certain point, I felt the need to consult an analyst. For six months, I went to her house once a week to clarify a few things. She was a doctor and psychoanalyst. She was always there.'

Although he did not specify what 'things' needed clarifying, Argentina was at the time under military rule with severe political suppression and many people disappearing.

He said: 'Then one day, before she died, she called me. Not to receive the sacraments, because she was Jewish, but for a spiritual dialogue. She was a good person. In those six months she really helped me.'

Francis told the French writer he now felt liberated. 'Of course, I'm in a cage at the Vatican, but not spiritually. Nothing frightens me.'

The candid admission will be published in Wolton's book on September 6 as Pope Francis departs on an official visit to Columbia.

Asked whether he still suffers from anxiety Francis said: 'When I get on the plane (at the start of an official trip) and I find myself in front of journalists (the Vatican press corps), I have the feeling that I'm going into the lion's den. I start to pray, then I try to be very precise.'

The Pope's Jesuit order is known for its respect of psychoanalysis and he has spoken about it before, explaining why he chose to sleep in a modest guesthouse instead of the Vatican's grand Apostolic Palace, he said: 'It's for psychiatric reasons. I can't live alone, do you understand?'