Last week, NHS Digital released the results of a major survey of adolescent mental health. The findings suggest that one in eight five- to 19-year-olds in England has a clinically impairing mental health condition, while one in 20 meets diagnostic criteria for two or more clinically impairing mental health conditions. This means that, on average, three pupils in a class of 24 will be struggling with poor mental health.

Previous research shows that, for many children, such difficulties persist, and that half of those meeting diagnostic criteria will also meet diagnostic criteria for the same mental health condition three years later.

In the following analysis, I will talk through the statistics in detail and explain why they matter to teachers and schools.

Why is this survey important?

In short, because it is a highly controlled and very accurate survey that enables long-term analysis. This is the third in a series of government-funded surveys and followed the same methods, as far as possible, as the studies conducted in 1999 and 2004 to allow for comparison.

More than 9,000 children and young people aged 2-19 were selected from the NHS patient register to provide a representative population-based sample. The involvement of children under the age of 5 and above the age of 16 makes it an unusual and valuable study internationally.

In contrast to many other recent reports about child mental health, which draw on administrative data from service access and prescriptions or brief questionnaires, this survey employed a detailed, multi-informant, standardised diagnostic assessment with every child or young person. This makes it more accurate - and of more use, to teachers in particular - for the following reasons:

• Even when standardised diagnoses are used in other surveys, they tend to employ a brief questionnaire to select children and young people for more detailed assessment. This two-phase approach can save time and money, but as no screening questionnaire is 100 per cent accurate, the results are less reliable.

• The use of multiple informants improves the accuracy of the mental health assessments. The parents of all 2- to 16-year-olds were interviewed, as were the parents of older teenagers, provided that the young person consented. Similarly, young people aged 11 or older were interviewed and, if the family agreed, a questionnaire was mailed to a teacher that they nominated. As well as mental health, the interviews covered access to services, plus background characteristics and experiences selected after extensive consultation with key stakeholders.

• The standardised diagnostic assessment was administered by trained interviewers, then a small team of mental health practitioners reviewed all the information collected from parents, young people and teachers to make the assessment process as similar to clinical practice as possible.

• The nature of the assessment meant the professionals involved were able to see if a parent, teacher or young person had misunderstood what was being asked, and could spot children who would fall through the gaps in the diagnostic manual, but who nonetheless had clinically significant difficulties. The clinical raters assigned diagnoses of mental health conditions according to the 10th edition of the World Health Organization’s International Classification of Diseases.

So is the mental health of children and young people deteriorating?

There is no doubt that referrals to CAMHS, clinical diagnoses of autism spectrum conditions (ASC), and prescriptions of antidepressants and attention deficit hyperactivity disorder (ADHD) medications, as well as presentations to accident and emergency departments with self-harm, have all significantly increased over the past five-to-10 years.

These increases do not necessarily signal that the mental health of children and young people in the community has worsened, but they may be driven by a greater willingness to seek help, improved identification of difficulties or changes in clinical practice.

Indeed, an analysis of data from community samples across Great Britain over 20 years did not provide clear evidence of poorer mental health in terms of scores on the questionnaires used. Yet over this time, more parents and young people reported concerns that they had a mental health problem when asked.

Some differences with the 2017 survey were unavoidable; the previous surveys used the child-benefit register as a sample frame, but, as it is no longer a universal benefit, this approach would not have generated a representative sample.

The comparisons described below necessarily focus on the narrower age range (age 5-15) and include only the types of mental health condition studied in previous surveys.

The survey confirmed a modest increase in the prevalence of mental health conditions overall among five- to 15-year-olds, from 9.7 per cent in 1999 to 10.1 per cent in 2004 and 11.2 per cent in 2017. This represents a statistically significant increase from 1999 to 2017, but not from 2004 to 2017.

The prevalence of emotional disorders (approximately 4 per cent) did not change between 1999 and 2004, but had risen to nearly 6 per cent among five- 15-year-olds in 2017, and was apparent for both boys and girls.

In contrast, the prevalence of behavioural disorders and ADHD did not demonstrably change.

Similarly, the prevalence of ASC and eating disorders, which were only included in the 2004 survey, was similar in 2017.

While any increase in the proportion of school-age children who have clinically significant mental health conditions is obviously concerning, the increase is modest and may not fully explain the recorded increase in referrals, clinical diagnoses and prescriptions.

How many children are struggling with poor mental health?

Among children and young people aged 5-19 in 2017, 12.8 per cent met diagnostic criteria for one or more mental health condition, as did 5.5 per cent of two- to four-year-olds. The children were more likely to have poor general health, and live with a parent with poor mental health and unhealthy family function, and to be classified white British.

With the exception of young people with eating disorders, all mental health conditions occurred more frequently in children whose families were on a low income or in receipt of benefits. Overall, there was no difference between the proportion of boys and girls with poor mental health, although there were gender differences in the types of condition identified.

Boys were more likely to be diagnosed with ADHD, ASC and behavioural disorders, which were more common among preschool and primary-age children; girls were more likely to be identified with emotional and eating disorders, which increased significantly in adolescence.

These findings are consistent with the earlier surveys, and many others worldwide.

The prevalence of mental health conditions increased steadily with age, from 5.5 per cent of two- to four-year-olds to 9.5 per cent of five- to 10-year-olds, 14.4 per cent of 11- to 16-year-olds and 16.9 per cent of 17- to 19-year-olds. This increase was more pronounced among young women than young men. It is mostly due to the greater increase with age in the prevalence of emotional disorders among girls, and particularly high rates of emotional disorder in young women aged 16-19 (22.4 per cent) compared with boys of the same age (7.9 per cent). This echoes the findings of the most recent adult mental health survey, which included people from age 16 upward. Although using different methods and assessments, it also identified especially high levels of anxiety and depression among younger women.

Educators working in key stage 5, therefore, may face notable challenges in supporting young people in general, and young women in particular.

Emotional disorders, by which we mean clinically significant anxiety and depression, can affect appetite, sleep, and the ability to think clearly and concentrate, with obvious implications for a child’s ability to function in school.

They often commence in childhood or adolescence, and run a fluctuating, episodic course. Fewer than half of the young people who are affected maintain their recovery into early adult life, while many experience repeated recurrences.

Anxiety disorders comprise a range of conditions in which extreme worry and fear cause significant distress, or they consistently prevent the child from coping with ordinary activities.

Depression as a diagnosis, as opposed to ordinary sadness, involves persistent, unrelenting low mood, irritability and lack of energy, such that the capacity to enjoy, or sometimes even undertake, ordinarily pleasurable activities is impaired.

Behavioural disorders or persistent, repetitive, disruptive or aggressive behaviours that violate social norms, are of obvious importance to educators. That these problems are no longer the most common mental health condition in children and young people is only because of the increase in emotional disorders.

The numbers of primary and secondary school-age children identified with behavioural disorders was similar but consistently higher among boys (five- to 10-year-old boys at 6.7 per cent and girls at 3.2 per cent, 11- to 16-year-old boys at 7.4 per cent and girls at 5 per cent). The prevalence in 16-19 years was strikingly low (1 per cent of boys, 0.5 per cent of girls), which may be due to fewer parent and teacher reports being obtained for this age group, or a lower level of recruitment among those with behavioural difficulties when the individual themselves rather than the parent was the key informant.

Some people question whether or not behaviour that challenges others should be considered a mental health condition, but a childhood diagnosis of conduct disorder predicted all adult mental health conditions in the Dunedin cohort (bit.ly/DunedinStudy), including anxiety, depression and psychosis. Their educational, occupational and health outcomes are very poor compared with children without these difficulties. Robust evidence exists for the effectiveness of parental training courses but on their own, they’re unlikely to solve school-based problems.

We are beginning to acquire evidence for school-based interventions that are urgently needed.

School-based factors

As with the previous surveys, teachers were the most common “service” contacted within the previous year about mental health; contact with teachers was reported by 48.5 per cent of those with a mental disorder.

Education support services were accessed by 22.6 per cent of those with a disorder, and educators should be proud that they achieved the highest level of satisfaction.

Importantly, there was no reported contact with professionals in relation to mental health for one in four young people with a disorder, underlining the importance of the designated mental health leads and school-based mental health teams proposed in the government’s Green Paper on young people’s mental health provision (bit.ly/MHGreen).

Over a third of children with a disorder had recognised special educational needs, while half of those with and without recognised special educational needs had an education, health and care plan. The survey was not able to ascertain the reason for the special educational needs, but it is probable that, for some children, the special educational need related directly to their mental health condition.

Nearly two-thirds of children with ASC (62.9 per cent) and ADHD (68.8 per cent) had identified special educational needs, compared with only a quarter with emotional disorders. The last of these are frequently less evident in school, although anxiety may prompt opposition and rule breaking, as a child tries to avoid what they are frightened of, or the lack of energy, motivation and irritability inherent in depression may be mistaken for laziness and disobedience.

The highly social and repeatedly changing nature of the school setting is hugely challenging for children with ASC to navigate, even when they are intellectually able, while the difficulties in sitting still and concentrating that comprise ADHD often cause greater difficulties, as academic demands increase at school.

Teachers reported that 1.7 per cent of five- to 16-year-olds recorded unauthorised absence from school, which was more common among those with mental health conditions. This ranged from 0.8 per cent of children without a disorder to 5.5 per cent of those with hyperactivity, 9.7 per cent of those with an emotional disorder and 11.2 per cent of those with a behavioural disorder.

According to parental report, 1.2 per cent of five- to 16-year-olds had experienced a fixed-term or permanent exclusion from school. Exclusions were more frequently reported if the child had a mental health condition (6.8 per cent versus 0.5 per cent) and were most common among those with hyperactivity (11.7 per cent) or conduct disorder (11.6 per cent). Among children with these conditions, approximately one in 20 reported three or more exclusions from school, which suggests a need for more effective support for this group.

Bullying is arguably our most tractable public mental health problem, which casts a shadow over adult as well as child mental health, and commonly centres on school peer groups. Effective interventions exist, but as one in five 11- to 19-year-olds reported being bullied over the previous year, we need to do better in their implementation. The experience of being bullied was more frequently reported by girls than boys (25.8 per cent versus 16.7 per cent) and twice as common among those with a mental health condition.

In summary

These long-awaited statistics indicate an increase in mental health conditions in children and young people. The rise in emotional disorders is concerning, and young women in their mid-teens in particular seem to be vulnerable. The impact of mental health on children’s ability to cope with school is evident by the high levels of contact with teachers and educational support services, special educational needs, truancy and exclusion. Previous research highlights the considerable cost attached to mental health-related contact in the education system. Even with increased demands on services in recent years, a quarter of those with impairing mental health conditions had no professional contact within the previous year. The Green Paper proposals provide a much-needed opportunity to better identify and support those who struggle, as does the mandatory inclusion of mental health in PSHE.

Tamsin Ford is professor of child and adolescent psychiatry at the University of Exeter College of Medicine and Health, and worked on Mental Health of Children and Young People in England, 2017, which can be read at bit.ly/MHCSurvey2017