There has been relatively little research investigating the prevalence of mental disorders in toddlerhood and early childhood, even though mental health issues occurring at this time in life could have a lifelong impact. Classifying mental disorders is challenging at this early age because of rapid changes in physical and mental abilities including the ability to regulate and control one’s own behaviour and emotions. Many behavioural or emotional problems occurring at this stage are typically explained away as being transient rather than more lasting indications of mental disorders. Furthermore, the continuum between typical and atypical development is blurred. Refusing to cooperate, shouting “no”, stamping feet, will be something many parents of children aged 2-4 years will be familiar with. Recall the episode from the famous TV show ‘Friends’ where in one scene little Ben is with his father Ross, and Ben’s mother (Carol) arrives home:
Carol: Hey! How’s Ben?
Ross: Well, I asked him if he wanted to eat, he said, “No.” I asked him if he wanted to sleep, he said, “No.” I asked him what he wanted to do, he said, “No.” So, he’s sweeping.
Although in 2016, the Diagnostic Classification of Mental Health and Developmental Disorders of Infancy and Early Childhood (DC: 0–5; Zero to Three, 2016) was developed for children aged 0-5 years taking into account the normal age-associated development and pathological manifestations of disorders, it is not widely used; with current diagnoses in children following the ICD and the DSM diagnostic systems which are meant for adults.
The present paper conducted a meta-analysis to identify the worldwide prevalence of mental health problems in the age group of 1-7 years in community samples (Vasileva et al, 2020).
The authors followed the PRISMA guidelines as well as the search strategy followed by previous meta-analytic studies on the prevalence of mental disorders in children. Thus, a systematic search for relevant literature was conducted on Web of Science, PsycINFO, PSYNDEX, MEDLINE, and Embase databases. Epidemiological studies of community samples published between 2006-2020 and using standardised procedure for diagnosing at least three disorders as per the DSM- IV, DSM-IV-TR, DSM-5, ICD 9/10, or DC: 0-3/ DC: 0-5 were included.
R software was used to perform the meta-analyses. The authors assessed the pooled prevalence of any mental disorder (combined proportion of people with any mental condition at any given time period), any specific mental disorder as well as comorbidity (simultaneous presence of two or more conditions) in this sample. Pooled effect sizes and confidence intervals (95%) were also calculated and interpreted. Moderators were also investigated, including but not limited to factors identified in an earlier meta-analytic study by Polanczyk et al (2015). These included study location, sample frame, diagnostic instrument, study design, functional impairment, number of diagnoses, and age group. Biases in publication were also assessed.
The sample included 18,282 children (that comprised 10 independent community samples) across 17 studies in the age range of 12-83 months. Parent reports were used to assess symptoms in the present or up to 3 months in the past. These studies were conducted in 8 countries (USA, Brazil, Denmark, Iraq, the Netherlands, Norway, Romania and Spain) and relied on birth registers (4 studies) or primary care practices (3 studies).
Findings showed the overall prevalence rates of any mental disorder to be 20.13% with substantial heterogeneity between studies.
The highest overall prevalence rates with respect to specific disorders were identified for:
- ADHD (attention-deficit hyperactivity disorder) (2.73% [95% CI: 1.3 to 5.8] to 4.27% [95% CI: 2.5 to 7.2])
- ODD (oppositional defiant disorder) (3.90% [95% CI: 1.8 to 8.3] to 4.90% [95% CI: 2.5 to 9.5])
- Specific phobias (2.36% [95% CI: 0.8 to 6.7] to 3.23% [95% CI: 1.3 to 8.0])
- Feeding disorders (1.36% [95% CI: 01.3 to 6.3] to 2.89% [95% CI: 1.7 to 4.7])
- Sleep disorders (1.65% [95% CI: 0.5 to 4.5] to 2.89% [95% CI: 0.8 to 1.0]).
Out of the 10 studies, 7 assessed the prevalence of comorbidity of two or more disorders. The pooled prevalence of comorbidities was 5.51% and excluding an outlier (a study by Petresco S et al, 2014), this prevalence rate increased to 6.44%.
Meta-regression analysis found sample frame, diagnostic instrument, study design, functional impairment, number of diagnoses, and age group to be non-significant predictors of heterogeneity in prevalence rates of any mental disorder. No publication bias (which refers to presenting only statistically significant findings since they attract publication) was found for most analyses, except for ODD and reactive attachment disorder.
Estimating the worldwide prevalence of mental disorders among children aged 7 years or less, the authors reached the conclusion that:
every fifth child suffers from a mental health problem
every third child with a mental disorder fulfils the criteria for at least one further psychiatric diagnosis.
Strengths and limitations
Despite the limited number of epidemiological studies of mental disorders among 1-7 years old community samples of young children, this meta-analytic study has made a significant contribution to the literature in identifying the prevalence of mental disorders in young children. It has highlighted the need for conducting more epidemiological studies for assessing mental disorders in this age group, where it is challenging to accurately identify mental disorders due to overlap with developmental changes. This study brings to fore the high prevalence rates of mental disorders and comorbidities in young children, which suggests the urgent need for better assessment and treatment of mental health issues in this age group. The study also included a large sample size, making the findings more reliable.
However, informant bias (potential error that can occur due to the fact that the subjects of study aren’t reporting for themselves but an informant is reporting on their behalf) cannot be ruled out as the reason for higher prevalence rates since parents reported on their children’s symptoms while older children and adolescents reported for themselves. It is also important to note here that the reported prevalence rates may not be representative of the worldwide prevalence as the samples were mostly restricted to developed Western countries from Europe and America. The prevalence rates are likely to vary in Eastern community samples and in developing countries. Moreover, these findings were based primarily on studies that used the DSM-IV criteria (which is meant for diagnosing mental problems in adult populations) and none of the studies included were based on the latest criteria in DSM-V or the ICD.
These findings highlight the importance of conducting more community studies among developing and LMICs (low and middle income countries), where mental health issues are still a largely neglected area considering the limited budget allocated to mental health treatment and research by the governments in such countries. Though there is increasing awareness among these countries regarding the importance of good mental health, the long-prevailing cultural stigma and lower literacy around mental health issues have led to the neglect of diagnoses of mental health issues in children. Thus, the possibility of higher prevalence of mental health problems among young children in these LMICs as compared to that among developed countries cannot be denied and needs to be explored in future research. Such problems among young children going undetected, and therefore untreated, would pose serious long-term effects in their lives. Since the latest version of DSM (DSM-V) also recognises and incorporates culturally-sensitive diagnostic criteria for various disorders, there is a need to develop tools (or adapt existing tools) for assessing mental health problems in children, which are sensitive to the culturally-manifested symptoms of mental health disorders.
Implications for practice
Findings from the present meta-analysis highlight the need for more research to be undertaken among young children which are specific to each developmental stage (such as infancy, toddlerhood, etc.). Further, it draws attention to the need of early identification and treatment of childhood mental disorders and highlights the need of using developmentally-sensitive criteria for classifying mental disorders. Specifically, since most of the children in the sample had received a single diagnosis, early treatment could prevent the possibility of developing co-morbidities. However, about one-third of the diagnosed children also had comorbidities of mental disorders, and therefore a more intensive intervention and approach to treatment is required in these children.
Statement of interests
We have no conflict of interest.
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