Discussion

Using healthcare register record linkage in Wales, we assessed both the annual and lifetime prevalence of CAMHS contact among children and adolescents. Over a 12-month period in 2004, 0.8% of the total child and adolescent population had contact with CAMHS, compared with the 12-month period in 2022, where this had risen nearly five-fold to 3.9%. In raw numbers, this reflects an increase from 4665 to 19 870 young people accessing CAMHS per year. In terms of lifetime prevalence (up to age 18 years) of CAMHS contact, among the birth cohort born in 1991 who turned 18 in 2009, 5.8% had attended CAMHS at some stage in childhood or adolescence. For individuals born in 2005 who turned 18 in 2023, however, this figure had risen to 20.2%.

Reliable information on the prevalence of service use is important because there is a distinction between the epidemiological burden of mental disorders in the population and the proportion of the population seeking specialist mental health services. For instance, national survey data from England suggest that only a minority of young people in the general population who would meet criteria for a mental disorder were in contact with CAMHS. ^{Reference Ford, Hamilton, Meltzer and Goodman21}

Of note, our data only reflect individuals who attended CAMHS and not the high numbers on waiting lists for services, ²² meaning the true demand for CAMHS is likely to be significantly higher even than the 20% figure in the most recent birth cohort. Research in England suggests that less than half of referrals to CAMHS are accepted. ^{Reference Sayal, Wyatt, Partlett, Ewart, Bhardwaj and Dubicka23} Further, the data reported here only indicate that an individual had at least one contact with CAMHS and they do not necessarily imply that an intervention or treatment was received.

Notably, while our findings pertain specifically to Wales they are likely to be generalisable across the UK given the similar structure of CAMHS provision in all four nations. In fact, the prevalence of CAMHS attendance may be even higher in Scotland, England and Northern Ireland due to their greater service capacity relative to Wales. ²⁴

Rates of CAMHS contacts were significantly higher for adolescents in comparison with children, with as many as 7.6% of adolescents having had one or more CAMHS contact in 2022 (the most recent year for which we have full data). This high rate of adolescent CAMHS attendance likely, in part, reflects the level of risk associated with the types of disorders that are more prevalent in adolescents in comparison with children (e.g. self-harm, eating disorders), increasing the likelihood that these type of referrals are accepted. The data also showed a growing disparity in terms of the numbers of adolescent girls versus boys attending CAMHS. There were only minor differences in the proportions of boys versus girls attending in the early 2000s. In 2022, however, 10% of all adolescent girls had one or more CAMHS contact, compared with 5.4% of boys. The high and increasing prevalence of CAMHS use among adolescent girls, in particular, is consistent with findings that this group has had a rising prevalence of mental health problems (particularly in internalising and eating disorders) over the past three decades. ^{Reference Bor, Dean, Najman and Hayatbakhsh2,Reference Potrebny, Nilsen, Bakken, von Soest, Kvaløy and Samdal3,Reference Collishaw, Maughan, Natarajan and Pickles6,Reference Tick, van der Ende and Verhulst7} On the other hand, the proportion of adolescent boys attending CAMHS peaked in 2018 at 6.2% and has not exceeded this figure since, highlighting important sex differences.

The reasons underlying the increasing prevalence of CAMHS contact are complex and multifaceted, reflecting both factors driving an increasing prevalence of mental disorders in young people and factors that specifically promote mental health service demand. Many researchers have suggested that the COVID-19 pandemic has contributed to an exacerbation of mental health help-seeking among children and adolescents. ^{Reference Deng, Zhou, Hou, Heybati, Lohit and Abbas25,Reference Madigan, Racine, Vaillancourt, Korczak, Hewitt and Pador26} Our findings, however, spanning nearly two decades, place year-on-year increases in a wider context and do not support the idea that the trajectory of increasing presentations to CAMHS can be directly attributed to the pandemic (other than being associated with a decreased number of attendances in 2020). While this does not mean that there were not pandemic-related mental health impacts on some young people, our findings indicate that the increasing trend of CAMHS presentations predates COVID-19, demonstrating the problems inherent in analysing changes over a limited number of years rather than taking into account trends over a longer period of time. Notably, the COVID-19 pandemic is just one of a number of global intensifying crises, such as climate change, war and increasing economic hardship, all of which may also be contributing to trends in youth mental health.

In terms of factors that have specifically contributed to the rise in mental health service demand, it has been proposed that increased awareness around mental health problems, resulting in earlier detection and better identification of mental illness, has led to increased service demand. ^{Reference Wei, McGrath, Hayden and Kutcher27} Mental health awareness efforts may have reduced stigma surrounding mental illness, reducing barriers to help-seeking. ^{Reference Clement, Schauman, Graham, Maggioni, Evans-Lacko and Bezborodovs28} Another factor may be the impact of efforts to improve the accessibility of CAMHS, such as the increasing availability of telehealth services. ^{Reference Boydell, Hodgins, Pignatiello, Teshima, Edwards and Willis29} However, population research has indicated that the prevalence of mental health symptoms are increasing in the adolescent population, ^{Reference Potrebny, Nilsen, Bakken, von Soest, Kvaløy and Samdal3,Reference Collishaw, Maughan, Natarajan and Pickles6,Reference Tick, van der Ende and Verhulst7} along with the severity of these symptoms, ^{Reference Armitage, Newlove-Delgado, Ford, McManus and Collishaw30} suggesting that the observed rise is unlikely to be solely due to improved identification. Further, some researchers have argued that increased mental health awareness may not only be increasing help-seeking behaviour, but could also inadvertently contribute directly to rising mental health problems in teenagers. ^{Reference Foulkes and Andrews31}

Our data show a gradual year-on-year increase in adolescent presentations to CAMHS from 2004 to 2010. There was a sharp increase, however, in 2011, with this larger increase in attendances being maintained in 2012, 2013 and 2014. Between 2015 and 2018, attendances continued to grow but with smaller increases in numbers. This was followed by a drop in attendances in 2019 and a further (likely COVID-19 related) drop in attendances in 2020. Attendances increased again in 2022.

One potential contributor to increasing adolescent CAMHS contacts is the impact of austerity and increased income inequality in the UK. ^{Reference Karanikolos, Mladovsky, Cylus, Thomson, Basu and Stuckler32,Reference Ribeiro, Bauer, Andrade, York-Smith, Pan and Pingani33} There is evidence that the incidence of mental disorders rose in several European countries following the 2008 financial crisis. ^{Reference Gili, Roca, Basu, McKee and Stuckler34,Reference Kentikelenis, Karanikolos, Papanicolas, Basu, McKee and Stuckler35} Austerity measures in the UK have resulted in reduced funding to health, education and social services in Wales. ^{Reference Roberts and Charlesworth36} These cuts have likely exacerbated existing inequalities, potentially contributing to negative impacts on young people’s mental health. ^{Reference Brown, Gao and Song37} Our data, however, show that the increasing prevalence of CAMHS attendance pre-dated the 2008 financial crisis, though the trajectory increased more rapidly from 2011. While financial crises are known to have harmful effects on the health of the entire population, the current mental health crisis seems to be disproportionately affecting adolescents, ^{Reference McGorry, Mei, Dalal, Alvarez-Jimenez, Blakemore and Browne11} suggesting there are also likely to be unique, developmentally specific drivers of the rise in presentations for mental ill-health in this age group.

Another consideration might be the proliferation of smartphone use among teenagers, leading to increasing time being spent online, as well as the proliferation of social media engagement – notably, Instagram launched in 2010. The majority of the evidence on the impact of social media exposure on young people’s mental health, however, comes from cross-sectional studies, making it difficult to infer causality, ^{Reference Valkenburg, Meier and Beyens38} and it is likely that relationships are bidirectional. ^{Reference Sanders, Noetel, Parker, Del Pozo Cruz, Biddle and Ronto39} Nonetheless, that the increasing pattern of CAMHS attendance seems to disproportionately affect adolescent girls aligns with recent findings indicating age- and sex-specific windows of sensitivity to the effects of social media use. ^{Reference Orben, Przybylski, Blakemore and Kievit40} It is feasible that there may be sensitive periods during adolescence where young people are particularly vulnerable to the impact of social media on mental health. Another possibility is that the rise in mental health problems is a result of increasing fragmentation of interpersonal and societal connectedness. ^{Reference Wickramaratne, Yangchen, Lepow, Patra, Glicksburg and Talati41} Supporting this, research suggests that young people in more socially connected societies appear to have better mental health. ^{Reference Ougrin, Woodhouse, Tucker, Ronaldson and Bakolis42}

It is also notable that, while online activity has increased for adolescents, physical activity has decreased, with girls having lower physical activity levels than boys. ^{Reference Guthold, Stevens, Riley and Bull43} Decreased physical activity may also play a contributory role in declining mental health, though the evidence on the relationship between exercise and mental disorders in adolescents is of low certainty. ^{Reference Rodriguez-Ayllon, Cadenas-Sánchez, Estévez-López, Muñoz, Mora-Gonzalez and Migueles44}

The dramatic change, over a relatively short period of time, in the population who had contact with CAMHS raises a number of important clinical questions. To what extent can the CAMHS interventional evidence base, generated from studies that were often conducted decades ago, be applied to current clinical cohorts? That is to say, if the target population has exponentially increased without evidence to support their “equivalence” to the original target population, at what stage does an intervention change from being evidence-based to being experimental?

Re-evaluating the effectiveness of CAMHS interventions is particularly important in the context of a number of studies demonstrating that outcomes for CAMHS cohorts are often poor, both in the short-term ^{Reference Sayal, Wyatt, Partlett, Ewart, Bhardwaj and Dubicka23} and long-term. ^{Reference Healy, Lång, O’Hare, Metsälä, O’Connor and Lockhart45} Sayal et al ^{Reference Sayal, Wyatt, Partlett, Ewart, Bhardwaj and Dubicka23} for example, followed young people attending CAMHS for 12 months and found persistently high levels of self- and parent-reported mental health symptoms, functional impairment and self-harm. Healy et al ^{Reference Healy, Lång, O’Hare, Metsälä, O’Connor and Lockhart45} followed former CAMHS patients to approximately age 30 and found that these individuals went on to take up more than half of all adult mental health service out-patient appointments and more than half of all adult psychiatric in-patient bed days. What’s more, approximately half of severe mental illnesses diagnosed in the population by age 30 occurred in individuals who had attended CAMHS, including 50% of schizophrenia diagnoses, 48% of bipolar disorder diagnoses, 49% of recurrent depression diagnoses and 54% of borderline personality disorder diagnoses.

The rapid changes in numbers in contact with CAMHS highlights the need for real-time access to service use data, as well as the need for a greatly increased research capacity to keep pace with the rapidly increasing service use. Currently, mental health service data in the UK are spread across different data custodians and the processes to access these data are complex and time intensive. ^{Reference Ford, Mansfield, Markham, McManus, John and OReilly46} Data are not routinely collected on the type and severity of difficulties experienced by young people attending CAMHS, nor are data on whether young people who attended CAMHS accessed or benefited from treatment. Further, there is a lack of research infrastructure to carry out this work, including, but not limited to, a paucity of clinical academics working within CAMHS. ^{Reference Kelleher, Poziemska, Kieseppä, Thapar, Dubicka and Lockhart47}

Strengths of the study include the use of whole population data captured in prospective administrative data which is free of selection and recall bias. A limitation of the data is that we were only able to include individuals who were enrolled with a GP (representing ∼83% of the Welsh population), and only included those who had continuous GP registration between ages 5 and 18 years. This is likely to disproportionately exclude specific populations, such as refugee populations and those with high residential mobility, both of whom are at increased risk of developing mental health problems. ^{Reference Blackmore, Boyle, Fazel, Ranasinha, Gray and Fitzgerald48,Reference Tseliou, Maguire, Donnelly and Reilly49} Second, complete information on CAMHS contacts was not available until 2004, meaning that complete information on CAMHS use in childhood may not have been available for the older birth cohorts. However, we did have complete adolescent CAMHS contact data for all cohorts and since adolescent contacts comprise ∼70% of all CAMHS attendances, the missing childhood data likely has minimal impact on our lifetime prevalence estimates (evidenced by similar rate increases for any CAMHS contact (3.48-fold) versus adolescent-only contact (3.18-fold)). Private mental health service contact was not captured in the available data. These limitations, however, mean we are likely to have underestimated, rather than overestimated, the prevalence of CAMHS contact. CAMHS contact that occurred in earlier years, however, may have been more likely to be underestimated and this may account for some of the differences identified. Further, data for the 2023 year was incomplete (available from January to November only), which prevents direct comparison of the 2023 data with the other complete calendar years. Lastly, we were not able to assess the duration or frequency of CAMHS contact nor the specific diagnoses or treatment offered. The data only reflect whether an individual ever had contact with CAMHS, which limits our understanding of the actual impact on resources, as we cannot assess the depth or nature of service utilisation in relation to increased contact. Lastly, we acknowledge that there are concerns around the accuracy of medical coding; however, our prevalence estimates align with previous cross-sectional surveys of CAMHS attendance, ^{Reference Signorini, Singh, Boricevic-Marsanic, Dieleman, Dodig-Ćurković and Franic50} suggesting contact with CAMHS has been reasonably accurately coded in our data-sets.

In conclusion, there has been a dramatic increase in the number of young people attending child and adolescent mental health services in Wales over the last two decades. For the earliest-born (1991) cohort, 1 in 17 attended CAMHS in their lifetime but this has now increased to 1 in 5 young people for those born in 2005. The rapid change in numbers in contact with CAMHS raises serious concerns for the state of child mental health in the UK. Failure to treat mental health conditions can lead to poor long-term health, education and social outcomes, highlighting the urgent need to scale-up evidence-based mental health support for young people. The results also raise important questions about the evidence base for existing CAMHS interventions, which are often based on trials conducted decades ago, potentially with very different populations. There is a need to prioritise more intensive research activity within CAMHS to improve our understanding of the factors driving these increases in presentations but also, in the context of a rapidly changing target population, to evaluate the effectiveness of existing CAMHS interventions and to develop new, evidence-based interventions that are fit for purpose.