It was more intimidating than an Old Firm game, he told the audience.

Neil Lennon, the former Celtic captain, spoke candidly yesterday of his battle with the depression which crippled his confidence and left him "a complete shell, a total wreck".

Lennon, 36, who now plays for Nottingham Forest, was launching a new study on recovering from long-term mental health problems, carried out by the Scottish Recovery Network (SRN).

Their book, Journeys of Recovery, draws on the personal experiences of nearly 70 people across Scotland to highlight factors that helped and hindered their recovery from a range of conditions.

Lennon told an audience at Glasgow Royal Concert Hall that speaking about his experience of depression was "a bit nervy - and worse than playing in an Old Firm game".

He said that for much of his Celtic career he "pretended to be fine" but was "absolutely dying inside".

"I am the last person you would think of as depressed - someone who is as confident, cocky and aggressive as me," he said.

"But when it first hit me I became a complete shell, a total wreck. I could not focus on anything I did. I did not want to play football, or even get out of bed in the morning. Even when we won an Old Firm game I had no sense of joy.

"I didn't know what was wrong with me. I felt I couldn't speak about it publicly because I didn't want it to be an excuse for bad performances."

Lennon's road to recovery began with daily visits to the Celtic club doctor, Roddy Macdonald, whose understanding was the key to helping him to come to terms with his depression.

"I never thought I was going to get better," Lennon said. "But you can recover. I haven't been unwell for two years now but I am still in recovery. I am still on light medication - it keeps me on an even keel.

"I want to send a message that it's all right to have it depression. No-one should be ashamed to talk about it because anyone can get it in any walk of life."

SRN is an affiliation of organisations and individuals with an interest in researching and raising awareness of mental health problems and mental illness.

It is part of the Scottish Government's National Programme for Improving Mental Health and Wellbeing.

In its research, it interviewed 67 volunteers who suffer from mental illness.

After comparing the people's testimonies, researchers found that, unsurprisingly, the most important factor was a willingness to get well and a belief that recovery is possible.

Developing an acceptable personal identity - defining oneself by something other than one's mental illness - was a crucial step towards moving forward and coping with the condition.

The quality of treatments and services were also important. Patients complained that they never saw the same doctor twice and could not establish a relationship with someone whom they found helpful.

Others reported a lack of support services outside normal working hours.

Simon Bradstreet, network director of the SRN, said: "People need to hear about recovery because our research shows that believing it can happen is the first step. It sounds like common sense but this has not happened in the past."

He added: "We need to increase access to crisis support outside office hours. If you can help people when they first identify symptoms you can prevent people from developing more serious illness."

Shona Robison MSP, Minister for Public Health, said: "This report provides a message of hope. It does not suggest that recovery is straightforward but it does show that recovery is possible.

"For many people a key factor was belief in that possibility of recovery. For friends, family members and wider community alike there is a responsibility to share and support this message of hope - and to raise expectations."