The majority of children in a key study on puberty blockers saw their mental health deteriorate, new analysis suggests.

In the original study of 44 children, no evidence of mental impact, either benefit or harm, was discovered.

But a re-analysis of the information shows that 34% saw their mental health decline, while 29% found it improved.

This re-evaluation has been carried out by Professor Susan McPherson, from the University of Essex and David Freedman, a retired social scientist.

In the study, the word 'deteriorated' could mean going from being psychologically well and not needing treatment for mental health, to getting a diagnosis such as depression or anxiety.

What the re-analysis and the original research doesn't explain is why there is such variation between the children on the study.