More than 70,000 people under 18, including nearly 2,000 primary school children, have been prescribed anti-depressants in England over the last year, new figures show.
But experts have called for caution in giving the drugs to youngsters, warning that potential long-term effects on developing brains are not fully known.
Mental health campaigners say access to other treatments, such as "talking therapies", should be made more widely and easily available as a first resort.
GPs have said the prescription figures are evidence of youngsters seeking treatment, which is encouraging, but have backed calls for greater access to other therapies.
NHS data obtained by The Times through freedom of information requests showed 7.3 million people were given at least one antidepressant prescription in England in 2017.
The drugs were used by one in six adults, the statistics suggested, with the total number marking an increase of nearly 500,000 since 2015.
The number of anti-depressant prescriptions has more than doubled in the last decade.
A psychiatrist at Oxford University, Andrea Cipriani, told the paper that doctors needed to be careful of prescribing anti-depressants to the developing brain.
"We don’t know the long-term consequences," he said.
A 2016 review by Dr Cipriani found most available anti-depressants did not help children and teenagers with serious mental health problems and some could be unsafe.
The review of clinical trial evidence found that of 14 anti-depressant drugs, only one – fluoxetine, marketed as Prozac – was better than a “dummy” placebo at relieving the symptoms of young people with major depression.
Another drug, venlafaxine, was associated with an increased risk of suicidal thoughts and suicide attempts.
However, the study concluded that the true effectiveness and safety of anti-depressants taken by children and teenagers remained unclear because of the poor design and selective reporting of trials, which were mostly funded by drug companies.
Head of the Royal College of GPs, Professor Helen Stokes-Lampard, said on Friday that it was “important that (the) figures aren’t automatically seen as a bad thing,” however she warned of a “severe lack” of other options available to doctors.
Tom Madders, spokesman for the charity Young Minds, said prescribing antidepressants to youngsters was appropriate in some circumstances, although they should not be used as a “sticking plaster for poor access to talking therapies”.