Children's mental health services will need to expand significantly to cope with the growing problems faced by young people, the head of the NHS in England has said.
Simon Stevens said higher rates of mental illness combined with a greater willingness of people coming forward with problems meant there would have to be a "major ramp up" in services.
In an interview with Parliament's The House magazine, he also commented on the debate over whether cannabis should be legalised for medical purposes, saying there is "some evidence" it can be effective for certain conditions.
Mr Stevens said there is a need to address the causes of young people's mental health, including their "negative" experiences online and on social media.
"There is a higher rate of genuine mental health distress and at the same time as that's become part of the public dialogue and stigma has reduced, people are willing to come forward. So, we've got both of those going on at the same time," he said.
"The consequence is that as a result, we're going to need a major ramp up under any scenario of young people's mental health services. That's got to be one of the big things that comes out of the long-term NHS plan."
Mr Stevens said he expected new survey results to be published later in the year to show a significant increase in young people experiencing poor mental health.
This would, he said, inevitably lead to questions over the causes and that social media companies and schools needed to become involved in the search for answers.
"There is a growing awareness that alongside some of the positive aspects of children's online experience and social media, there are some important negatives," he said. "We've just within the past week had WHO (World Health Organisation) recognise gaming addiction as a new disorder. So, this is something that has got to be looked at by schools, by social media companies."
The debate around medical marijuana has been reignited by the case of Charlotte Caldwell, who has waged a battle with the Government after the Home Office seized a supply of cannabis oil she tried to bring into the UK for her severely epileptic son Billy.
Mr Stevens said the issue must remain separate to whether it should be legalised for recreational use, stressing it can cause psychosis for some.
"We should have an entirely evidence-based look at whether there are compounds derived from cannabis that are effective for certain health conditions," he said. "There is some evidence to suggest that that's true: conditions such as multiple sclerosis, chemotherapy-induced nausea and so on."
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