Common mental disorders prevalence in adolescents: A systematic review and meta-analyses

1Common Mental Disorders (CMD) refer to depressive and anxiety disorders and are distinct from the feeling of sadness, stress or fear that anyone can experience at some moment in life. Despite some methodological differences in the epidemiological studies, it is estimated that 4.4% and 3.6% of the world adult population suffers from depressive and anxiety disorders, respectively. CMD can affect health and quality of life, and it is noted that CMD affect people at an early age.

2The Global Burden of Diseases, Injuries, and Risk Factors (GBD) study is a comprehensive study that evaluates incidence, prevalence, and years lived with disability (YLDs), which in its most recent study evaluated the period from 1990 to 2017 for 195 countries and territories, and identified that the burden of mental disorders is present for males and females and across all age groups. The findings of the GDB indicate that mental disorders have consistently formed more than 14% of age-standardized YLDs for nearly three decades, and have greater than 10% prevalence in all 21 GBD regions. Mental disorders are not often correctly identified and have negative consequences on people's health.

3At the population level the use of self-report psychiatric screening instruments, such as the General Health Questionnaire (GHQ), has been recommended to track CMD, also known as psychological distress/problems or psychiatric morbidity or non-psychotic mental illnesses. The GHQ-12 is a short and self-report form to identify people with psychological distress or CMD. This validated instrument comprising a multidimensional evaluation based in three factors: anxiety and depression, social dysfunctions and loss of confidence and can be applied in individuals of different ages.

4Adolescence, defined as a transitional phase between ages 10 and 19 is generally perceived as a phase of life with no health problems. However, approximately 20% of adolescents experience a mental health problem, most commonly depression or anxiety.

5Although there are preliminary data on the severity of these conditions among adolescents, there has been a lack of knowledge about the magnitude of CMD in adolescents worldwide. There was a systematic review of the global prevalence of CMD, published in 2014, which incorporated studies from 1980 to 2013 that surveyed people aged 16 to 65 and using diagnostic criteria other than GHQ. In addition, from this study it was not possible to identify the prevalence of CMD in adolescents. In this context, a systematic review of the literature was carried out to estimate the prevalence of CMD in adolescents around the world, from item 12 of the GHQ.

6This systematic review followed the Preferred Reporting Items for Systematic Review and Meta-analyses PRISMA checklist and for meta-analyses followed Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines.

7The systematic review protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42018094763.

8The present study included observational studies. Only studies that assessed the prevalence of CMD according to GHQ-12 in adolescents (10 to 19 years old) were considered for retention. In studies that evaluated adolescents and also individuals outside the age group of interest for this review, an attempt was made to identify only those eligible through the information contained in the article or by contacting authors.

9Moreover, no restrictions of language, publication date or status were applied. Studies of specific groups such as obese or diabetic individuals, adolescents in treatment of any health condition, college students, people who had traumatic experiences, pregnant teenagers and people with physical disabilities were not eligible. The ineligibility criterion considered those conditions that predispose to a higher risk of CMD, such as life events that presumably increase the chances of having feelings of stress, depression or anxiety. For example, among college students depression rates could be substantially higher than those found in the general population, probably because they experience moments of stress related to studies or future choices involving the profession phase of life. Systematic reviews, interventional studies or ecological estimates were also not included.

10A systematic search of the following databases was conducted to identify relevant studies: Medline, Embase, Scopus, Web of Science, Lilacs and Adolec. A partial grey literature search was also performed in Google Scholar, PsycINFO and Proquest Dissertation and Theses. The Google Scholar search was limited to the first 200 most relevant articles. The search was conducted on December 1, 2018 and updated in April 1, 2019. Additional articles, were hand-searched in selected articles to identify potentially eligible studies not retrieved by the database search. The search strategy was reviewed by two researchers, one of them with extensive experience in systematic reviews, according to the criteria of the checklist of the Peer Review of Electronic Search Strategies (PRESS checklist).

11The following strategy was adapted for the databases: (Adolescent OR Teenager OR Child OR Young OR Teen OR Youth OR Juvenile OR Adolescence OR Younger) AND (“General Health Questionnaire” OR GHQ OR GHQ-12) AND (“common mental disorders” OR CMD OR Anxiety OR anxious OR depression OR dysthymia OR “generalized anxiety disorder” OR “panic disorder” OR phobia OR “social anxiety disorder” OR “obsessive-compulsive disorder” OR “mental disorder” OR “mental health” OR "Psychological stress" OR "Life Stress" OR "Psychologic Stress" OR "Mental suffering" OR Anguish OR "Emotional stress") AND (Survey OR “Cross-sectional studies” OR Prevalence OR frequency OR "Cross-sectional" OR Observational). More information on the search strategies is provided in S1 Appendix. The Covidence Software (Cochrane Collaboration software®, Melbourne, Australia) was used to remove duplicate references and for the screening procedure, applied independently.

12The study selection process was carried out in two stages. First, the articles were selected based on their titles and abstracts, followed by a full text assessment. These two stages were carried by two independent authors (SAS and SUS) and the records that did not meet the inclusion criteria were discarded. The disagreements were resolved by consensus and counted on the participation of a third author (DBR).

13Data were extracted in duplicate by authors and discrepancies were resolved by consensus. The following data were collected: authors, year of publication, year of research, country, study design, age (mean or range), sample size (sex), GHQ cut-off point and outcome of the studies (prevalence of CMD). The corresponding authors of the studies were contacted (at least two attempts of contact) in case of unavailable data.

14The 12-item version of the GHQ has psychometric properties comparable to those of the longer versions of the questionnaire and the items of this instrument describe positive and negative aspects of mental health in the last two weeks and present a scale with four response options. The difference in the scale for positive and negative items indicates that the higher the score, the higher level of psychiatric disorders. The studies show great variation in the scoring methods for the GHQ, with scales ranging from zero to 12 or zero to 36.

15The critical appraisal tool, recommended by The Joanna Briggs Institute for cross-sectional studies, was used to assess the risk of bias. The purpose of this appraisal is to assess the methodological quality of a study and to determine the possibility of bias in its design, conduct and analysis. This instrument consists of nine questions answered as “yes”, “no”, “unclear”, or “not applicable”.

16For this study, when all items were answered “yes”, the risk of bias were considered low, and if any item were classified as “no” or “unclear”, a high risk of bias were expected. No scores were assigned; results were expressed by the frequency of each classification of the evaluation parameters. These ratings were not used as a criterion for study eligibility.

17The primary outcome was the prevalence of CMD, with a confidence interval of 95% (CI 95%). We estimated the summary measures for the total population and subgroups defined by sex, risk of bias and income level according to the World Bank classification. The meta-analyses were calculated using a random-effect model and weighed by the inverse of the variance. The heterogeneity was evaluated by the Chi-square test with significance of p<0.10, and its magnitude was determined by the I-squared (I2).

18Meta-regressions were performed in order to identify possible causes of heterogeneity using the Knapp and Hartung test with the following variables: risk of bias, sample size, proportion of female adolescent, year of study and income level. The small-study effect by visual inspection of the funnel graph and Egger's test was also evaluated.

19Analyzes were performed with the "Metaprop" command of the Stata software (version 14.0), adopting p<0.05.

20A total of 6 351 articles were initially found in the nine electronic databases, including grey literature. After removing the duplicates, the titles and abstracts of 3 783 articles were screened, and 197 potentially relevant studies were selected for full-text reading. An additional record was selected from the reference lists of the fully read articles. A total of 126 articles were excluded for nominated reasons (see S1 Table). Forty-three studies (reported in 72 articles) were therefore selected for inclusion in this review. The screening process is detailed in Fig 1.

21Table 1 shows a summary of the study characteristics. A total of 43 studies (200 980 participants; 19 countries) were included. The CMD prevalence studies were conducted in Asia, America, Africa, Europe and Oceania. The majority of studies (n = 33) had a cross-sectional design.

22For the purpose of comparing the studies, we selected only those that presented the score scale from zero to 12, totaling 32 studies classified by 3 or 4 diagnostic cut-off points. Thus for the set of studies that adopted the cut-off point of 3 or more symptoms of the GHQ-12, the sample size varied from 145 adolescents in India to 74 589 in Brazil, these studies included 96 842 adolescents between the ages of 12 and 19 years. In the set of studies with cut-off point of 4 or more symptoms, it ranged from 90 adolescents in Malaysia to 17 920 in Japan and the total sample was 79 892 adolescents aged 12 to 19 years.

23Only six (18.8%) studies were considered to be of low risk of bias. Considering that the GHQ is a self-administered instrument composed of validated questions and translated in several languages, the parameter that deals with the identification of the outcomes measured in a valid way was met by all the studies.

24Two parameters were not met by most studies: (1) appropriate statistical analysis; and (2) study subjects and the setting described in detail (Fig 2 and Table 2). It is important to emphasize that the critical appraisal tool recommends that the numerator and the denominator be clearly reported, and that the percentages should be given with confidence intervals, so in the methods section there must be enough details to identify the analytical technique used and how specific variables were measured in the study. In addition, the study sample should be described in enough detail so that other researchers can determine if it is comparable to the population of interest to them. It is worth mentioning that some studies have reported the year of data collection and characteristics of the study population.

25Among those that adopted the cut-off point of 3 or more symptoms, the prevalence of CMD was 31.0% (CI95% 28.0–34.0; I2 = 97.5%). In studies that used the cut-off point of 4 or more symptoms, the prevalence of CMD was 25.0% (CI 95% 19.0–32.0; I2 = 99.8%) (Fig 3). In the subgroup analysis, the heterogeneity remained high and it was observed that CMD is higher in female adolescents when considered the cut-off point 3 (Table 3).

26In the meta-regression, the high heterogeneity could not be explained by the studied variables: sex, income level and year of publication (p>0.05; data not shown).

27The funnel graph was able to show the asymmetry between the studies, with greater representation of large studies (Fig 4). Graph A shows the studies that adopted cut-off point 3 and graph B, those that used cut-off point 4. Both illustrate that there is an effect of small studies and these findings were confirmed by the Egger's Test (p<0.001).

28This systematic review was able to reveal the magnitude of CMD in adolescents from all over the world. When presented at this stage of life, CMD can have negative consequences throughout the future years. The problem is common and worrying, so much has been widely studied since the 1980s however, they refer to studies with diverse populations and with different ways of identification of CMD.

29Mental health can be influenced by several factors. Socioeconomic characteristics; characteristics of lifestyleand also characteristics related to affective relationships, have been the focuses of studies already performed in adolescents.

30Our meta-analysis revealed that very large studies were conducted in Japan and United Kingdom. It was reported that children and adolescents in Japan have greater depressive tendencies and this condition may be growing each year in several countries. In the United Kingdom, the assessment and monitoring of psychological distress among adolescents is a common practice and generally performed in longitudinal studies for more than two decades.The evidence indicates that the relationship between culture or personal values and mental disorders differs across cultures and age groups. An approach that takes into account the differences in social and cultural contexts is necessary to understand the occurrence and phenomenology of CMD in epidemiological studies, since there is a relationship between them but that needs to be better clarifies in future studies.

31Although with some degree of methodological issue in most studies, since less than 20% of the studies presented low risk of bias, the results of this study indicate that CMD affect girls more, considering only the studies that adopted cut-off point 3. Permanent concern with physical appearance, body dissatisfaction, exposure to sexualization may be one of the reasons that affect girls' mental health.

32Another factor that apparently influences the presence of CMD is income level. Even though the results presented in this systematic review showed no difference between income level of the countries and CMD, further studies with this focus are needed in order to deepen the knowledge about the subject. Longitudinal studies such as the British Household Panel Survey (BHPS) and Longitudinal Study of Young People in England (LYSPE) demonstrate the impact of economic recession and poverty in populations by strong associations between socioeconomic variables and health outcomes.

33Although the GHQ is a validated instrument for detecting CMD, the scoring scale and cut-off point are not consensual, which impairs comparison among studies. Meta-analyses in the present study were based on cut-off points 3 and 4, since they were more frequent among the studies.

34In relation to age, studies are commonly defined to be representative of the population aged 15 years or more, however, it is also important to investigate the phenomenon of CMD among the younger population (10 to 14 years), since global epidemiological data consistently report that up to 20% of children and adolescents suffer from a disabling mental illness. Particular attention should be paid to the most vulnerable adolescent population in order to create strategies based on scientific evidence. This systematic review revealed the severity of the problem by the worldwide high prevalence of CMD among adolescents, using a standardized criterion of measurement, the GHQ-12.

35In this review some of the eligible studies showed association data and did not present the prevalence and the respective confidence intervals, nor did they present the description of the evaluated population. It is possible that this review did not include all relevant publications, either because the articles did not present sufficient information or because the authors were not located or, finally, because of unanswered communication attempts.

36It is observed that the different cut-off points for the GHQ-12 adopted in the original studies were a complicating factor in the identification of cases of CMD and in the comparison among studies. Even if measures were taken to combine studies that were as comparable as possible, this review included studies conducted at different times and places and with varying methodologies. These characteristics are revealed in the heterogeneity between the studies, typically found in cross-sectional studies and, therefore, we performed a subgroup analysis and a meta-regression, but without success.

37In the elaboration of this systematic review, some steps were considered as the registration of protocol in PROSPERO, the use of the PRESS checklist, blind selection of studies, the adoption of updated analytical methods and a search strategy that enabled the capture of a large numbers of studies. An extensive search for studies was carried out in the literature sources, the grey literature, and the reference lists of the eligible articles. When necessary, the authors of potentially eligible studies were contacted to obtain extra data to carry out the meta-analyses. Moreover, this systematic review followed the PRISMA tool guide and the Meta-analysis of Observational Studies in Epidemiology (MOOSE).

38The global prevalence of CMD in adolescents was 25.0% and 31.0%, using the GHQ cut-off point of 4 and 3, respectively. CMD was more prevalent among girls when observing studies that adopted a 3 cut-off point. These results point to the need to include mental health as an important component of health in adolescence and to the need to include CMD screening as a first step in the prevention and control of mental disorders.