The charity's report, Access Denied – A Teenager’s Pathway through the Mental Health System, found that children and young people are made to wait, on average, 66 days for an initial assessment by specialist mental health services.
Find out more about child mental health at 'Parental Mental Health and Child Welfare' on 2 December in London
But in some areas waits for conditions including severe depression and anxiety, self-harm, eating disorders and psychosis, stretch to 140 days – almost five months. By contrast, there are six-week targets in place for many physical health conditions.
Matthew Reed, Chief Executive of The Children’s Society, said: "Too many young people are struggling to access the support they need to overcome mental health problems. Children who are referred to specialist services for help with serious mental health conditions often need urgent support to prevent a problem from becoming a crisis. What they are getting at the moment, too often, is rejection, confusion and delay.
"Access to mental health support for even the most vulnerable teenagers – including victims of sexual exploitation – is patchy, in part because of a lack of clear national guidance on how they should be helped. This needs to change and we urge Government and health trusts to work together, alongside charities like ours on the frontline, to do more to help young people in their time of need."
Although waits for children aged 10-17 are improving in some areas, and have improved slightly overall in the past year, almost a third (31%) of providers reported an increase in waiting times for so-called Tier 3 Children and Adolescent Mental Health Services (CAMHS) between 2013/14 and 2014/15.
Thresholds for accessing care
Delays may be associated with increases in young people seeking help. Referral rates to specialist mental health services for children and young people rose by more than 40% between 2003 and 2010, research by Durham University found. In the last year around 200,000 children have been referred for specialist support.
The Government has recently pledged to introduce new access and waiting time standards for young people dealing with eating disorders by April 2016 – but not for other mental health problems, including those related to abuse or neglect.
Even children deemed to be vulnerable following experience of abuse, exploitation, neglect, violence or drugs problems are struggling to get help, with more than one in four (28%) young people referred being rejected or re-directed to lower-level services following an initial assessment.
One of the reasons why significant numbers of young people are being denied specialist support is the very high thresholds for accessing mental health services in particular areas, the report concluded.
As a result, the charity is calling for new standards on access and waiting times for all mental health conditions. It is also calling on the Department of Health to set out clearly, in national statutory guidance, the rights of young people to receive different levels of support for various conditions, as well as stating which cases should be fast-tracked, to tackle the postcode lottery of treatment.
Psychologist Linda Papadopoulos added: "Young people need help at the right time to stop mental health problems worsening and continuing into adulthood. In the most extreme cases, not getting help early enough can lead to children taking their own lives. The fact young people are being forced to wait months for support, and are often being turned away completely, shows just how urgently action is needed."