There has been a substantial drop in the number of young people with mental health problems who have to be treated in non-specialist wards, a new report revealed.

In 2015-16 there were 135 cases where under-18s were treated either in an adult psychiatric ward or a hospital children's ward, down from a record of 207 the previous year.

A total of 118 youngsters were admitted to these non-specialist wards in 2015-16, the Mental Welfare Commission said, compared to 175 in 2014-15.

In the NHS Greater Glasgow and Clyde the number of these admissions fell by 53% over the year while in the Lothian area the drop was greater at 62%, with Grampian reporting a 44% decrease.

Colin McKay, chief executive of the Mental Welfare Commission, said: "When young people are so unwell that they need hospital treatment for mental ill health, they should wherever possible be treated in a specialist unit. We were concerned in recent years at the rising numbers who were not receiving this treatment.

"Today's figures show a substantial, and very welcome, drop in the numbers admitted to non-specialist wards. We hope this will be sustained and even improved upon in future.

"The change has come about due to a combination of new beds becoming available, improved intensive community support and improved processes and more stable staffing in specialist units."

The NHS has three specialist in-patient units in Scotland for treating under-18s with mental health problems - in Glasgow, Edinburgh and Dundee.

The report pointed out there is no specialist intensive psychiatric in-patient care for this age group, stating while the number affected was low (14), adult intensive psychiatric care units are "highly specialised environments" with doctors having voiced fears about their suitability for treating young people.

The Mental Welfare Commission also highlighted the "limited access to education" there was for some young people who were receiving in-patient care and added it was "disappointed" that there had been a drop in access to appropriate activities for this age group.

Mr McKay said: "An adult ward can be a difficult and alienating environment for a young person.

"That is why it is so important that the care is informed by specialist expertise, and the young person has access to age-appropriate recreation and activity."

The vast majority of admissions to non-specialist wards last year saw under-18s being treated in adult wards while in three of the 135 cases young people were treated in a paediatric ward.

The most common reason for young people to be taken into hospital for treatment was deliberate self-harming or suicidal behaviour, with almost half (49%) of the cases where more detailed information was available involving this.

In just over a quarter (26%) of cases, the admission was because of concerns about possible or actual psychosis.

In 27% of admissions, the young person spent between one and three days being treated on a non-specialist ward, there were 12 cases where patients were there for five weeks or more.

Mental Health Minister Maureen Watt said: "We take the mental health of our young people very seriously and are investing an extra £150 million in mental health over five years.

"We have also doubled the number of child and adolescent mental health service psychology posts in recent years.

"More young people are coming forward to seek help as the stigma surrounding mental health declines."