Every child in Scotland will need additional mental health support as a consequence of measures taken to tackle the coronavirus crisis, according to the country’s children and young people’s commissioner.

Speaking exclusively to the Guardian as he publishes Scotland’s comprehensive assessment of the impact of the pandemic on children’s rights – the first such review undertaken anywhere in the world – Bruce Adamson said the pandemic had sent a “very negative” message about how decision-makers value young people’s voices.

He said Scotland has been viewed as a children’s rights champion but that efforts to involve young people in the dramatic changes being made to their education and support “went out the window as soon as lockdown came along”.

There have been escalating concerns across the UK about children’s mental health after support structures were stripped away at the start of lockdown. Earlier this week, the Guardian revealed that five children with special educational needs have killed themselves in the space of five months in Kent, amidst warnings over the impact of school closures on pupils.

Adamson said that lockdown measures have been “catastrophic” to children’s mental health, but that it remained difficult to quantify what additional support was necessary. “Children haven’t been in places where people with the right skills have been able to assess what they need, so schools, youth work, clubs, outdoor activities need to be very careful as children return.

“Even the most resilient children are going to need additional support as they navigate this transition back into whatever is the new normal. Take as a starting point that every child is going to need something extra and many will need a lot extra.”

Adamson underlines that there was no direct input from children and young people into decisions around the cancellation of exams, or the change to a new method of assessment, and no representation on the Scottish government’s education recovery group.

“In Scotland we’ve got a well-developed civil society that is good at supporting them to be involved, and we should have been able to deal with that when the system is under pressure. That sends a very negative message to children and young people that they are a luxury or an addition rather than an integral part of the decision-making process.”

The report, undertaken for the commissioner by the Observatory of Children’s Human Rights Scotland, highlighted the difficulties of assessing the impact of emergency legislation on vulnerable groups of children because of serious gaps in data collection, including inconsistent definitions of ‘vulnerable’ across central and local government and no collective data on the total numbers of children who are living in poverty, digitally excluded, or receiving mental health support services or additional support for learning.