IT took Mike (name has been changed) more than 20 years to realise he was suffering from an illness so common that as many as one in four of us could experience it at some time during our lives.

"I didn't know I was depressed until someone else pointed it out to me. I had all the symptoms but ever did anything about it," he admitted.

"I was gradually going downhill - I was sinking without realising it. Because I didn't realise I was depressed, I didn't see any reason to do anything about it."

Mike, 38, of Bournemouth, admits that it took a year of being "pushed and nagged" before he went to his GP. "I was absolutely at rock bottom. The only way I could describe it is that I had almost totally failed to function as a proper, normal person.

"When you feel like that, you don't want to go out, see people, talk to people. Every normal situation is a challenge beyond your capability."

His doctor diagnosed him as having clinical depression. "It gave me an answer to why I felt the way I did. I was relieved because I knew something could be done about it," said Mike.

He was prescribed anti-depressants and since February has been having cognitive behavioural therapy with clinical psychologist Kalpita Kund of Dorset HealthCare NHS Trust.

"The difference between having the blues and being clinically depressed is that clinical depression is an illness," she explained.

"If you ask a depressed person: 'Can you tell me about the future?', they usually say: 'What future?'.

"They have images in their head of dark clouds, feeling they are stuck, feeling they are inadequate. They are low within themselves: low self-worth, low self-confidence, feeling like a failure, not having achieved anything."

Kalpita added that women were twice as likely as men to experience depression.

Signs of depression may include loss of energy and concentration, disturbed sleep, significant weight gain or loss, and emotions ranging from anger, anxiety and irritability to frustration, guilt, resentment and sadness. In cases of severe depression, people may feel suicidal.

But if they can be persuaded to take the first step and go to the doctor, they do not have to go on suffering.

Research has shown that a combination of medication and therapy is the most effective treatment. After a referral from the GP, a psychologist will carry out an assessment, then discuss with him or her what the options are.

Cognitive behavioural therapy, which has proven effective in treating depression, involves the therapist and client working together over a set number of sessions.

"The client sets the agenda. We're not advising them to do anything. We help them put the jigsaw together," explained Kalpita.

"It's about helping them understand what's happening and making them more aware of what's going on in terms of their thought patterns; how they impact on work life, home life and relationships; and what they can do to cope more effectively with their problems."

Mike said: "Kalpita put me at ease very quickly. One of the things I was asked was what I wanted to get out of coming to see her. From the beginning it was to stand on my own two feet."

"Where I am now is very different from where I was six months ago. There's definitely light at the end of the tunnel. It's not necessarily that I won't feel low again. A lot of what Kalpita is doing here is giving me tools for coping with life. I'm coming back to being a functioning human being.

"Six months ago, the only thing I wanted to do was go to bed. I would be praying not to wake up in the morning. Now I am able to have plans for the future again and believe I will be able to achieve those."

Mike's message to anyone else feeling as he did is: "Go and seek help. Don't be afraid and don't worry about what other people think. Don't shut yourself off from other people, particularly the ones close to you. You're not alone - you're ill and illnesses can be treated. It's not a sign of failure."

Useful numbers: NHS Direct 0845 4647; MIND info line 0845 766 0163 (www.mind.org.uk); Bournemouth Poole and District MIND 01202 392910; Samaritans 0845 7909090