Mental health disorders occur in one in eight children and young people .The most common problems are internalising disorders such as anxiety and depression, with rates highest in females aged between 16 and 19 . At present, only one in four young people with difficulties within a clinical threshold will seek support from specialist Child and Adolescent Mental Health Services (CAMHS) . Furthermore, of those young people and families who are referred to CAMHS, one in four were not accepted into treatment . Demand outstrips supply to such an extent that some CAMHS services set their acceptance thresholds based on imminent risk to self or others, leaving many young people with treatable mental health conditions unable to access CAMHS or facing extra-ordinary waiting times .
Past research has focused on barriers to CAMHS access, which include demographic factors, including ethnicity, and indicators of social vulnerability, for example social care or youth justice service contact [4–6]. Peer, family and self-stigma, limited contact with adult caregivers who recognise mental need  and a lack of awareness to navigate the supportive services , are also known to prevent young people from seeking appropriate help. As these findings suggest, drivers of help-seeking do not just appear to relate to mental health symptom severity but also other contextual burdens that a young person is exposed to.
It is also possible that not all children, with mental health symptoms, who meet clinical disorders thresholds, have unmet needs. Those with a sufficiently positive quality of life – those with good home, school, social lives and a sense of autonomy - may experience much lower impact from their symptoms . For example, some children and young people may be able to manage their mental health challenges and maintain quality of life either through self-management or support from family or other supportive adults/peers, charities and online tools [1, 10].
At present, children and adolescent’s mental health problems have been largely examined using conventional symptom scales, for example Strengths and Difficulties Questionnaire (SDQ) as it is one of the most widely used measures in CAMHS [11, 12]. However, this emphasis on symptom scales has missed some important features of the mental health challenges that lead to contact with mental health services. In particular, less consideration has been given to the impact of mental health problems on day to day function and young people’s ability to derive meaning and enjoyment from life .
Furthermore, there has been little work conducted on how quality of life, especially young people’s self-rated quality of life, may relate to help seeking or the recognition of need by adult caregivers. A few longitudinal studies have examined mental health symptoms and environmental variables as predictors of adolescent rated quality of life, showing an expected association between both poorer family function, higher symptom severity and lower quality of life [14, 15]. However, as far we are aware, no studies have examined the longitudinal effect of quality of life on access to CAMHS that the conventional mental health difficulty measures may not capture, whilst taking into account other potential confounders including education attainment, school environment and family characteristics.
We aimed to address this limitation within this study. To do this, we used a population cohort study nested within a large-scale linkage between school and child mental health service administrative data. Using a historical cohort design, we examined longitudinal association between a young person’s self-reported quality of life (QoL) and a possible contact with CAMHS. We set out to estimate the strength of this relationship, whilst taking into account the severity of the young person’s mental health problems, and other potential confounders for CAMHS referral including ethnic, social-economic, social and educational factors.