A teaching union has linked a reported rise in self-harm amongst children to the "unrelenting" schedule of assessments in the new school curriculum.

The Scottish Secondary Teachers' Association (SSTA) acknowledged that the causes of self-harm are wide and varied, but said the curriculum and its assessments are a contributing factor to pupil stress and can damage pupil welfare.

The number of children admitted to hospital for self-harm doubled in some parts of Scotland between 2009 and 2014, according to NHS data obtained by the BBC.

ChildLine reported a 20% increase in counselling sessions in 2014, and mental health charity Penumbra reported a 166% increase in referrals since 2009.

Seamus Searson, SSTA general secretary, said the union "is acutely aware of the workload pressures associated with the National Qualifications but is extremely concerned as to the potential damage on our young people as the pressure intensifies at this time of year".

He added: "There is evidence that a rising numbers of pupils are being identified as self-harming.

"The causes of self-harm are wide and varied.

"But equally, we have to accept that school, the curriculum, the at times unrelenting internal assessment of our 15 and 16-year-olds between January and April is a contributing factor to pupil stress and can damage pupil welfare.

"How do we, as a teacher profession, respond to it?

"Teachers can question the pointless and often invalid assessment burdens. Teachers question the frequency and intensity of assessment faced by our 15 and 16-year-olds sitting N4 and N5."

He said an average pupil in S4 faces 24 assessments in at least six subjects between January and April.

One unnamed English teacher quoted by the SSTA said some of these assessments are "pointless" as they are not necessary for the exam, not valuable for progression and do not develop skills for work.

Euan Duncan, SSTA president, said: "Teachers have been, by and large, left to develop courses and assessments as they teach them.

"This is overbearing stress that experienced professionals, as adults, are struggling with and that stress is unintentionally, yet undeniably, being transferred and transmitted on to our pupils.

"The Government and the SQA need to review its current assessment requirements and accept the gathering of naturally occurring pupil's classwork and the use of teacher's professional judgement are sufficient and reduce the pressure on our pupils and the threat of self-harm."

The Scottish Government said it was not aware of any evidence to support a link between any suggested rise in self-harm and exam stress.

A spokesman said: "There is a range of mental wellbeing support available for young people in schools and it is for local authorities and school to decide on the best approaches, within Curriculum for Excellence.

"All schools should gather evidence about any mental health issues facing young people and take steps to provide the right support.

"The Scottish Government, working closely with the Scottish Qualifications Authority and Education Scotland, has provided an unprecedented level of support - including an additional £11 million since 2012 - to help teachers and schools prepare for Curriculum for Excellence and the National Qualifications."