Journal of Child Psychology and Psychiatry 56:3 (2015), pp 394–396


Commentary: Physical health outcomes and health care have improved so much, so why is child mental health getting worse? Or is it? A commentary on Collishaw (2015) Frank Verhulst

Department of Child and Adolescent Psychiatry, Erasmus University Medical Center – Sophia Children’s Hospital, Rotterdam, The Netherlands

The frequency of problems in children and adolescents varies between times within populations in the same geographical area. It has often been suggested, both in popular media as well as in scientific literature, that problems in children and adolescents have increased and that present-day youth fare less well than youth in the past. These concerns are fed by the assumed negative impact of societal change on individual development. It has been 20 years since Rutter and Smith (1995) published a book on various kinds of findings on child and adolescent problem behaviors that occur at different points in time in western societies in the latter part of the 20th century. They concluded that, despite a lack of rigorous epidemiological data, there was some evidence for a secular increase in adolescents’ conduct problems, substance abuse, depression and suicide. Fergusson (1996) wrote a critical notice in this Journal on the Rutter and Smith review. Interestingly, he argued that factors implied by Rutter and Smith as risks for adjustment problems, such as changes in social, economic, educational, family and other structures associated with child rearing and child development, may equally well lead to positive developments. He argued that increasing social diversity may lead to increasing variability in adolescent adjustment patterns with on the one end increasing numbers of young people showing psychopathology (as was shown by Rutter and Smith) and on the other end increasing numbers of young people who show responsible prosocial behaviors. However, there were no data available to test the possibility that social change has had both positive and detrimental effects for adolescents. More recently one may argue that the use of modern media may have similarly diverse effects, with negative impacts such as cyber bullying as well as positive impacts such as easier social communication. Rutter and Smith’s review also made clear that there were numerous methodological obstacles hampering firm conclusions about secular changes in rates of disorder that may well reflect changes in diagnostic criteria, use of mental health services, or record keeping such as police or suicide records. Typically time-trend studies of mental health problems

should involve a comparison of the rates of problems over time in one geographically defined population. If diagnostic criteria and assessment procedures are held constant over time, temporal trends can be determined. Twenty years ago, few epidemiological comparisons were available in which changes in problems in representative samples of children and adolescents from western societies at different points in time were assessed with similar standardized procedures. This situation has changed drastically over the last couple of years. In the current Annual Research Review, Collishaw, who is well-acquainted with executing secular trend studies himself, gives an impressively thorough overview of studies published over the last two decades on secular trends in child and adolescent mental health with an emphasis on studies that compare rates of child and adolescent problems over time in one geographically defined population (Collishaw, 2015). His main conclusion is that there is evidence for substantial secular change in the population prevalence in high-income countries of adolescent emotional problems and antisocial behavior, but not for childhood neurodevelopmental problems. Both periods of increase and decrease in symptom prevalence could be determined. The substantial increases in referrals of children and adolescents to mental health services are not reflected in changes in population prevalence of child and adolescent mental disorders. Collishaw’s review, which is a scholarly attempt to summarize the extent of changes in rates of child and adolescent adjustment problems over the last twenty years, leaves the reader with an overwhelming impression concerning the large variation in findings. Trends in prevalence of mental health problems of children and adolescents in high-income countries vary widely with type of problem, age, gender, country, period, source of information, and assessment methodology. Also, there is a multitude of possible explanations for any trends that have been observed, including changes in family life, and in socio-economic and cultural influences. The major strength of Collishaw’s review lies in the fact that it integrates findings of a large number of studies on trends in child and adolescent mental

© 2015 Association for Child and Adolescent Mental Health. Published by John Wiley & Sons Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main St, Malden, MA 02148, USA


health, in the discussion of possible explanations and its implications, and in the suggestions how to set priorities for future research. The review also raises a number of issues related to existing time-trend research worth mentioning. First, it is hard to understand contrasts between increased adolescent mental health problems over the last twenty years versus improvements in general physical health standards in most western countries (e.g. increasing life-expectancy and reduced infant mortality), as well as improvements in other societal standards including key indicators of educational performance and accessibility to health care facilities. In order to evaluate increases in problems such as anxiety and depression symptoms in children and adolescents, information on impairment in everyday functioning and of other indicators of child and adolescent well-being are crucial. For example, although there was a, significant though small, increase in parent-reported (but not in teacherreported or self-reported) internalizing problems in Dutch adolescents from 1993 to 2003, The Netherlands were among the countries showing the lowest multiple health problems in 11–15-year-old adolescents and the highest overall feeling of life satisfaction of 41 countries all over the world in a 2005–2006 survey (World Health Organization, 2008). Admittedly, this example pertains to just one area and is not very recent (e.g. does not cover the recent economic recession) but it highlights the importance of information on everyday functioning to interpret trends in population prevalence of mental health symptoms. There may be other reasons why prevalence estimates change with time such as shifts in thresholds for reporting problems, including greater parental sensitivity to children’s problems, or less tolerance to behaviors previously perceived as normal. Second, as Collishaw mentions, it is inherently difficult to test reasons for secular changes in mental health. One problem is that often time-trend information on possible exposures is analysed at the group rather than the individual level. Thus, we do not know, and hence cannot control for, the joint distribution of the combination of different variables at the individual level. For example, a time trend showing improvements in children’s emotional and behavioral adjustment in a US national sample was reported in one study, whereas in another totally independent US national survey, covering roughly the same period, rates of child maltreatment have reduced. Collishaw interprets these two separate findings by stating that reduction in maltreatment is likely to have contributed to these US trends in child psychopathology. However, since there were no data at the individual level, findings can be distorted by bias, making it hazardous to draw any causal inferences. Few time-trend studies are available that test time trends in child problems controlling for differences in hypothesized explanatory factors over time at the individual level (e.g. parental © 2015 Association for Child and Adolescent Mental Health.



psychopathology, family functioning). However, much of the evidence is still weak and future studies should focus on obtaining information over time on the individual-level on as many relevant non-global measures as possible. Third, some indicators of poor mental health, such as recent increasing suicide rates, are thought to be associated with economic recession. Although economic fluctuations may be related to suicide rates, effects of socioeconomic changes on child and adolescent mental health in general are complex and can be counter-intuitive. For example, Cederblad and coworkers utilized a quasi-experimental nature of two cross-sectional studies carried out 15 years apart in Khartoum, Sudan (Rahmin & Cederblad, 1984). This revealed a time trend in the prevalence of motherrated child problem behaviors. In 1964–1965 the authors observed few problems in children living in three villages lying on the outskirts of Khartoum, Sudan, despite poor nutrition and physical health. The largely rural communities subsequently underwent rapid urbanization and economic growth resulting in better housing, nutrition, sanitation, medical care, and education. Despite these improvements, the authors, who copied the methodology of the first study on to the second study, found that mothers reported more problems in their children in 1980. The authors argued that both changes in thresholds for perceiving behaviors as problems due to changes in social context and expectations as well as changes in the prevalence of problems might have accounted for this increase. For example, hyperactive behavior was regarded as a problem if children are expected to sit still in school, but went unnoticed in the traditional rural life when far less children attended school. On the other hand, headaches and stuttering would be considered discomforting in all social settings. As discussed later, there is now some evidence that, comparable to physical health indicators, also for mental health problems in children, it holds true that inequalities in income and possibly in other social factors drive health disparities. Fourth, time-trend studies often confound age, period, and cohort effects. For example, secular change and birth cohort membership independently contributed to elevated odds of obesity in recent generations of Americans, suggesting that cohortspecific strategies may be needed to prevent obesity. As Collishaw indicates, few time-trend studies of child and adolescent mental health problems have been undertaken that controlled for cohort effects. It is, however, a bit confusing that the term ‘crosscohort comparisons’ has been chosen to describe comparisons of repeat epidemiological samples assessed at different points in time in which period and cohort effects can be confounded, though admittedly the author warns the reader that differences can reflect either period or cohort effects or some combination of the two. There is one study, though not mentioned in the review, that used



accelerated longitudinal comparisons in which period effects could be controlled for age and cohort effects. In this 10-year follow-up of a Dutch general population sample originally aged 4 through 10 years, parent-rated aggressive and delinquent behaviors showed a secular increase from 1983 to 1993 (Stanger, Achenbach, & Verhulst, 1997). Fifth, inequality in income distribution is likely to be associated with children’s health, development and education, most likely due to inequality in access to health and social services, in education, and in a number of other aspects of society relevant to child development. The impact of social disadvantage can be detected from childhood onwards. There is compelling evidence that socio-economic differences can already be found in the intrauterine period and that health inequalities accumulate in disadvantaged families from the intrauterine period of children’s life onwards. The question is whether secular trends in income inequality can be found, and whether any changes in income distribution over time are associated with child and adolescent mental health. Collishaw briefly describes two studies, one in the UK and one in Finland, that show that the disparity in prevalence of emotional problems between different income groups increased. A problem with the UK study, however, was that the assessments of emotional problems were not done in exactly the same way in the most current versus the two earlier cohorts. The largest increase in emotional problem scores by cohort and family income were between the first two earlier cohorts. It is known that even small changes in the wording of questionnaires can have large effects in the prevalences that are reported. Nevertheless, these findings add to the debate about the recognition of health burden caused by social inequality. There is a need for studies with measures of income inequalities at the individual-level over time together with information on child and adolescent mental health and impairment measured with similar assessment procedures as well as measures of hypothesized explanatory variables. Last, does Fergusson’s critique on the Rutter and Smith review still hold? Collishaw’s overall conclusion that there is emerging evidence for secular increases in adolescent emotional and conduct problems is well supported. However, to fully understand the meaning of secular changes in mental health problems, it is essential to also have information on impairment and prosocial functioning. Admittedly, the parallel information on time trends in mental health problems and social functioning from both the US (Achenbach, Dumenci, & Rescorla, 2003) and Dutch (Tick, van der Ende, & Verhulst, 2007) studies show that changes in mental health problems over time are roughly accompanied by opposite changes in social competence scores, indicating that if children in a general population sample fare worse they generally do so in multiple areas. However, it is possible that children are differentially influenced by

J Child Psychol Psychiatry 2015; 56(3): 394–6

changes in external factors over time. It also remains to be answered to what extent changes in symptom prevalence over time are accompanied by changes in impairment. Collishaw has shown that progress has been made in the field of secular trend research of child and adolescent mental health problems. This type of research is needed to determine the impact of societal changes on child and adolescent well-being, especially with respect to changing income inequalities, both in high-income as well as low- and middleincome countries, and factors that mediate the association between inequalities and child and adolescent mental health.

Acknowledgement This Commentary article was invited by JCPP Editors and has been subject to internal review. F.C. publishes the Dutch versions of ASEBA from which he receives remuneration; he has no other competing or potential conflicts of interest in relation to this article.

Correspondence Frank Verhulst, Department of Child and Adolescent Psychiatry, Erasmus University Medical Center – Sophia Children’s Hospital, P.O. Box 2060, 3000 CB Rotterdam, The Netherlands; Email: f.verhulst@eras

References Achenbach, T.M., Dumenci, L., & Rescorla, L.A. (2003). Are American children’s problems still getting worse? A 23-year comparison. Journal of Abnormal Child Psychology, 31, 1–11. Collishaw, S. (2015). Annual Research Review: Secular trends in child and adolescent mental health. Journal of Child Psychology and Psychiatry, 56, 370–393. Fergusson, D.M. (1996). Critical notice. Journal of Child Psychology and Psychiatry, 37, 485–487. Rahmin, S.I., & Cederblad, M. (1984). Effects of rapid urbanization on child behaviour and health in a part of Khartoum, Sudan. Journal of Child Psychology and Psychiatry, 25, 629–641. Rutter, M., & Smith, D.J. (1995). Psychosocial disorders in young people: Time trends and their causes. Chicester: Wiley. Stanger, C., Achenbach, T.M., & Verhulst, F.C. (1997). Accelerated longitudinal comparisons of aggressive versus delinquent syndromes. Development and Psychopathology, 9, 43–58. Tick, T., van der Ende, J., & Verhulst, F.C. (2007). Twenty-year trends in emotional and behavioural problems in Dutch children in a changing society. Acta Psychiatrica Scandinavica, 116, 473–482. World Health Organization. (2008) Inequalities in young people’s health: Health behavior in school-aged children international report from the 2005/2006 survey. In C. Currie, S.N. Gabhainn, E. Godeau, C. Roberts, R. Smith, D. Currie, W. Picket, M. Richter, A. Morgan & V. Barnekow (Eds.), Copenhagen: World Health Organization. Available from: . . hbscinternational-report-from-the-20052006-survey [last accessed 5 January 2015].

Accepted for publication: 5 January 2015 © 2015 Association for Child and Adolescent Mental Health.

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Commentary: Physical health outcomes and health care have improved so much, so why is child mental health getting worse? Or is it? A commentary on Collishaw (2015).

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