The prevalence of a diagnosis of any psychiatric disorder at age 11 was 13.2 and 11.3%, respectively, when the DSM-5 and ICD-10 criteria were applied. The prevalence of any psychiatric disorder was higher among the male adolescents, mainly because ADHD/hyperactivity disorders and conduct/oppositional disorders were more common among the boys. The prevalence of any mood disorder, any ADHD/ hyperactivity disorder, and any psychiatric disorder was higher among adolescents belonging to families with a lower SEP than among those belonging to families with a higher SEP. Low maternal education, smoking during pregnancy, the presence of moods symptoms during pregnancy or maternal chronic and severe depressive symptoms in the first years of the adolescent´s life, male gender, 5-min Apgar score < 7 at birth and preterm birth were associated with higher odds of any psychiatric disorder at age 11.
The prevalence of psychiatric disorders among the adolescents in our sample is comparable to that reported in a recent systematic review and meta-analysis that included studies conducted in 27 countries and employed various methods of assessing psychiatric disorders [8]. Other studies from low- and middle-income countries, in which the DAWBA was applied, reported prevalence rates similar to those of our study. In a two-stage prevalence study of randomized samples of children between 5 and 10 years of age (n = 922) from three contrasting areas of Bangladesh [24], the overall prevalence of any psychiatric disorder was 15.2% (15.4% in rural areas, 10.0% in urban areas with a better SEP, and 19.5% in urban areas with a worse SEP). In a sample of 448 subjects between 7 and 14 years of age in Russia [29], the observed prevalence of psychiatric disorders was 15.3%, 70% higher than that previously observed in a comparable study of children and adolescents in Great Britain [30]. In a study involving subjects between 7 and 14 years of age in the southeastern region of Brazil [23], the reported prevalence of psychiatric disorders was 12.7%.
The rates of psychiatric disorders are generally higher in studies using screening instruments than in those using diagnostic instruments. A study conducted in the city of Taubaté, in the state of São Paulo, Brazil, evaluated 454 school children (7–11 years of age) at public and private schools [31]. Using the Strengths and Difficulties Questionnaire, the authors found that 35.2% of the subjects were considered positive for mental health problems, which reached clinical relevance in 22.7% and borderline relevance in 12.5%. The Estudo de Riscos Cardiovasculares em Adolescentes (ERICA, Study of Cardiovascular Risk in Adolescents), a cross-sectional school-based study conducted in Brazilian municipalities with more than 100,000 inhabitants, evaluated 74,589 adolescents [32]. Using the 12-item General Health Questionnaire, the authors found that, among the subjects between 12 and 14 years of age, the prevalence of common psychiatric disorders was 26.7%.
In the present study, the evaluation of the prevalence and symptomatology of psychiatric disorders was performed according to the DSM-5 criteria. Therefore, in addition to the specific differences between the DSM-IV and DSM-5, we included three nosological categories belonging exclusively to the DSM-5: DMDD; body dysmorphic disorder; and binge-eating disorder. DMDD, which is included in the DSM-5 depressive disorders section, was the main factor accounting for the difference of mood disorders prevalence between the DSM-5 and ICD-10 criteria. It should be noted that, according to the DSM-5, the symptoms of ODD often occur in children with DMDD, the main difference being that angry outbursts and the occurrence of the symptoms in more than one sphere (family, school, and social) are more common in the latter. Therefore, this new diagnostic category (DMDD) also explains the difference between prevalence rates for conduct/oppositional disorders when ICD-10 and DSM-5 are used.
In our study, the most common psychiatric disorders were anxiety disorders. A systematic review of 11 studies, using the DSM-III, Revised or DSM-IV diagnostic criteria, showed that the reported prevalence of any anxiety disorder in children under 12 years of age ranged from 2.6 to 41.2% [33]. The authors found that the most common anxiety diagnosis in that age group was separation anxiety disorder. Despite the notable variation in prevalence estimates, which is likely due to differences in methodology and the instruments used, the lifetime prevalence of “any anxiety disorder” in studies involving children or adolescents is between 15 and 20% [34].
In the present study, the prevalence of any ADHD/ hyperactivity disorder was similar to estimates reported for children and adolescents around the world (5.3% in individuals under 18 years of age) [19]. A recent cross-sectional study that assessed 1676 6-to-16 year-olds from four regions of Brazil using the Schedule for Affective Disorders and Schizophrenia for School-Age Children/Present-and-Lifetime-Version (K-SADS-PL) applied to mothers/main caregivers, reported a prevalence of any ADHD/hyperactivity disorder of 4.5% (CI 95% 3.5–5.6) [35].
Epidemiological and clinical studies have found gender-related differences in many types of psychopathology. Early-onset disorders (those that begin in childhood) are typically more prevalent in boys, whereas those that begin in adolescence are more prevalent in girls [36]. Such differences vary by age group. For example, most studies involving children report that the prevalence of conduct disorders, with aggressive and antisocial behaviors, is higher among boys than among girls. During adolescence, the prevalence of depression and eating disorders is higher among girls, who are also more likely to engage in suicidal ideation. Adolescent boys, however, have more problems with anger, more often engage in high-risk behaviors, and are more likely to commit suicide [37]. Contrary to what was observed in the ERICA study, in which the prevalence of common psychiatric disorders in subjects 12–14 years of age was higher in girls than in boys, in our study the prevalence of any psychiatric disorder was higher in the boys than in the girls [32]. Because our study involved subjects aged 11 years, the frequency of disorders by gender found in the current study may reflect the prevalence of disorders observed in childhood, which is different from the prevalence of disorders by gender observed in older adolescents.
The SEP is used in epidemiological studies as a measure of socioeconomic factors that influence the place an individual occupies within the structure of society [38]. Although there are several indicators of the SEP, schooling, income, and the wealth index are the most widely used. Poverty is associated with multiple environmental risk factors for psychopathology, such as parental unemployment, maternal anxiety/depression, child/adolescent maltreatment and trauma exposure and fewer resources to access good quality health care. A systematic review that evaluated the effects of the SEP on the occurrence of psychiatric disorders in children and adolescents reported that the prevalence of psychiatric disorders was higher among children and adolescents belonging to families with a low income and whose parents had a low level of education than among those whose parents had higher incomes or higher levels of education [39]. In our study, after adjustment for potential confounders, only poor maternal schooling was associated with higher risk of any psychiatric disorder at age 11.
In accordance with our results, many studies reported the association between fetal exposure to maternal smoking in pregnancy and several adverse offspring mental health outcomes [40, 41]. Recently, Talati et al. showed that birthweight did not mediate the association between the exposure and externalizing psychopathology, indicating that the mechanisms through which maternal smoking increases the risk of offspring psychopathology were not operating through lower birthweight [42].
Consistent with previous reports, we found that maternal depression, especially when it is chronic and severe, was a strong predictor of offspring psychiatric disorders [43, 44]. Even though the exposure to maternal depression appears to be a significant independent risk factor for offspring mental disorders, Barker et al. reported that multiple risk factors exposures strongly affect child psychopathology, increasing the risk over and above the influence of maternal depression [45].
In our study, both preterm birth and 5-min Apgar score < 7 were associated with psychiatric disorders at age 11. The Apgar score is widely used to report the status of the newborn infant immediately after birth. Even though numerous factors can influence the Apgar score, 5-min low Apgar scores have been associated with an increased risk of a wide range of neurological and psychiatric disorders [46, 47]. Preterm birth has also been identified as a risk factor for several psychiatric disorders in childhood, such as emotional problems, ADHD and autism spectrum, increasing the risk significantly as gestational age decreases [48, 49].
In the present study, 22.7% of the adolescents with psychiatric disorders had one or more psychiatric comorbidities. Anxiety disorders accompany most psychiatric disorders, including mood disorders, disruptive behaviors, eating disorders, and substance use disorders. The combination of anxiety disorders and mood disorders is so common that many authors have postulated that anxiety disorders are part of the developmental sequence in which anxiety is expressed early in life, followed by depression in adulthood [34]. Community studies in young people have shown a high degree of the co-occurrence of conduct disorders and ADHD, which is associated with a worse prognosis in behavioral disorders, including substance use disorders [50]. Disruptive behavior disorders are also frequently accompanied by mood and anxiety disorders, although parents and teachers often report fewer problems related to anxiety and mood than to externalizing disorders, which are more easily perceived and more difficult to manage. The presence of psychiatric comorbidity interferes with the evolution of the psychiatric disorder, making its course more chronic, with a worse prognosis and a worse response to treatment [18]. The prevalence of comorbidities tends to be higher in studies conducted at mental health facilities and such comorbidities tend to occur more frequently in the later stages of development. A recent study by Bordin et al. showed that comorbidity increased the likelihood of maternal recognition of emotional/behavioral problems in children and adolescents, an essential first step in the searching for treatment or support for their children [51].
Strengths and limitations of the study
Among the advantages of the study is that it was a population-based study, with face-to-face interviews, involving a large sample of adolescents. In addition, we used an internationally recognized instrument, designed to generate diagnoses of psychiatric disorders, that has been validated for use in Brazil and was applied by trained psychologists, thus ensuring the quality of the data. Another important point is that we employed the criteria of the recently published DSM-5, which follows internationally accepted diagnostic criteria. Furthermore, the proportion of non-respondents was low.
One limitation of our study is that it was based only on information obtained from the mothers or legal guardians, because the DAWBA was not administered to the adolescents themselves or to their teachers. Reports from teachers and self-reports from adolescents could reveal other symptoms not recognized by the mothers, contributing to a more accurate diagnosis of the psychiatric disorders.