Robbie's agony and ecstasy

Robbie Williams will take to the stage tomorrow before more than 100,000 fans - each one singing along adoringly to hits such as Let Me Entertain You, Angels and Feel. On stage, he is famous for his "cheeky chappie" persona, his energetic performances and obvious love of the reaction he is sure to receive from his audience.

At 29, and with millions of album sales and an £80 million record deal, Williams is every inch the successful pop star.

But, in his most frank interview yet, the singer reveals he is suffering from depression caused by ecstasy use. And for a year he has been taking anti-depressants, which he refers occasional ecstasy users suffer levels of depression four times higher than normal.

Serotonin, a hormone found in the blood, digestive system and brain, is the body's main mood regulator. Research suggests after ecstasy enters the bloodstream, it acts on blood cells to release serotonin. Although this produces a high, research suggests in the long term, it can deplete serotonin stores.

Psychologist Dr Cynthia McVey said: "People using ecstasy are putting their future mental health at risk as the full facts are not available."

Williams says he is now clean and sober.