However, she said, others may be "just responding to something that is happening to them".
She added: "If a child is being bullied and they have symptoms of depression because they are being bullied, what they need is for the bullying to stop.
"They need to feel safe again. They don't necessarily need anti-depressants or therapy."
She said too much rigorous testing and academic pressure was adding to anxiety in youngsters.
And she criticised 'nay-sayers' who say 'children need to be acclimatised to stress.'
She added: 'They're part of the problem...You cannot apply an adult amount of pressure to a child brain and expect them to cope."
'Being a teen is harder now'
Ms Devon also said being a youngster today was "harder than it has eve been".
She explained: "Yes, children have more stuff - more possessions. They have more of what they don't need.
"They have less of what they do need.
"Parents work long hours. Family time that is spent together is spent staring at a screen."
She said the culture of schools has become "fiercely competitive" as they push their children to strive academic excellence.
She added: "And all of this is exacerbated by the relentless pace that is set by the internet.
"Online, children face cyber bullying, advertising which tells them they're not good enough, pornography, airbrushed lives."
A report by the Commons Education Committee found a "significant number" of child and adolescent mental health services are turning away vulnerable young people for not meeting diagnostic thresholds or being without a stable placement - something experts told the inquiry was "disgusting and a huge self-esteem blow"