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Pistorius trial: What is Generalised Anxiety Disorder?

20 May 2014 Last updated at 13:20 BST

The judge in the Oscar Pistorius trial has ordered him to start daily tests on Monday to assess his mental state when he killed his girlfriend.

Judge Thokozile Masipa told the South African athlete to attend Weskoppies psychiatric hospital in Pretoria as an outpatient for a month.

It comes after a defence witness said the double amputee was suffering from Generalised Anxiety Disorder (Gad).

Michelle Roberts from the BBC's Health and Science team explains what Gad is, and why the trial has been delayed.