Introduction
Depression in the population is a public health concern due to high prevalence rates, early onset and its impact on children and adolescents, families, and communities (1, 2). Depression in adulthood is a debilitating mental illness with clear developmental patterns from childhood through adolescence (3). Moreover, depression in childhood increases the risk of future episodes during adolescence (4, 5), and it adversely affects quality of life, motivation and learning (6-8). Depression among adults is associated with problems regarding interpersonal relationships (4), substance misuse (9), self-harm and suicide (10). Furthermore, major depressive disorder among youth has the greatest impact of any disorder, with more than 40% of young people experiencing a severe negative impact on their life (11).
Common symptoms of depression in adults are decreased energy, loss of motivation and initiative, increased degree of irritation, impaired concentration and memory, poorer self-esteem, guilt, shame and worthlessness, poor night's sleep, weight gain or weight loss, and suicidal thoughts and actions (12). Equal diagnostic criteria are employed to define major depressive disorder in children/adolescents and adults. The one exception to this is that DSM-IV and 5 (12, 13) allow for irritable rather than depressed mood as a core diagnostic mood symptom for children/adolescents. In systematically comparing adolescent and adult major depression symptoms profiles, Rice et al. (2019) demonstrated that appetite, weight change, energy loss and insomnia were more common in adolescents, while loss of interest, anhedonia and concentration problems were more common in adults. Further, the results were similar for depressive symptom count and major depressive disorder (14).
The diagnostic criteria for depressive disorders are the same for children and adults, but children’s depression will be characterised by their cognitive development and developmental age. Among young children, emotional disturbances, aggression, passivity, anxiety, behavioural difficulties, instability and restlessness, hyperactivity, isolation and various physical disorders, such as abdominal pain, can be symptoms of depression. Among depressed 3-6-year-olds, it was found that the depression was strongly characterised by guilt and extreme fatigue (15).
A comorbid relationship has been found between depressive disorders among older children/young adolescents and bulimia nervosa (16), anxiety and behavioural disorders (17), neuropsychiatric disorders such as ADHD (18), obsessive-compulsive disorder (19) and language disorders (20).
Prevalence
The prevalence of depression has been reported to be rather low, 0.08 % among children 3-5 years of age and 1.7 % between the ages 6–11 (21). An increase in the prevalence rate has been demonstrated in the transition period from childhood to adolescence; for example, the prevalence among adolescents between ages 12–17 is reportedly 6.1 % and 7.7% (11). A meta-analysis including 26 studies indicated a lower prevalence among children compared to adolescents: 2.8% for those under age 13 and 5.6% between the ages of 13–18 (22). Reported prevalence of depression and depressive symptoms in adolescents varies across studies. Wartberg and colleagues reported an estimated point prevalence of depressive symptoms at 8.2% among adolescents 12 to 17 years of age (23), compared to Saluja and colleagues, who reported that nearly 20% of young adolescents in grades 6, 8, and 10 in the US report symptoms consistent with depression (24).
Many children and adolescents struggle with depression or anxiety throughout adolescence. However, only a small percentage of these children will have such severe symptoms that require treatment (25).
Incidence
The incidence of depression is reported as significantly lower than point-prevalence. Garrison et al. noted a 12-month incidence of 3.3% for major depression in adolescents aged 11–16 years of age, based on structured interviews about symptoms and impairment and having identified dates of onset and duration. In addition, Lewinsohn et al. recorded an annual first incidence rate of 5.7% for major depressive disorder among high school students.
Gender differences
Before puberty, boys and girls appear to have similar rates of depression (22, 28). However, gender differences have been reported to emerge between the ages of 13 and 15 years, and the point prevalence of depression after puberty is preponderant in girls (about 2:1) (29, 30). Gender differences in a 12-month prevalence was found among older adolescents in a study of adolescents 15–19 years of age. For DSM-III-R major depressive episode, Haarasiltaet al. reported a 12-month prevalence of 6.0% among girls and 4.4% among boys, and observed in their study that 17.3% of girls between 12 to 17 years of age met the criteria for 12-month major depressive episode compared to 5.7% among boys.
Methodological challenges
Most studies investigate the occurrence of depressive symptoms among teenagers (23, 33, 34). In contrast, there is a lack of population-based studies examining depressive symptoms among the younger age groups. Furthermore, most studies report results based on only one assessment. A point-prevalence often provides merely a “snapshot” of how adolescents perceive their mood. Adolescence is a period characterised by transitions and shifting relationships and emotions (35-37) and have demonstrated that adolescents often report transitory depressive symptoms. Thus, to explore and evaluate the difference between point-prevalence and time-point prevalence, a study is warranted to examine the same sample repeatedly. Moreover, to our knowledge, no study has examined point prevalence, 12-month prevalence, and 12-month incidence among a representative sample of adolescents aged 11 to 14.
The aim of this study is to assess potential gender differences in point prevalence, 12-month prevalence, and 12-month incidence rates among children in 6th to 10th grade (age 11–14 years) by administering an established and robust self-report questionnaire twice within a twelve-month interval.
Method
Participants and procedure
All pupils in 6th –10th grade from 27 schools in two municipalities were invited to participate in the study. These two municipalities function as a representative sample of Norway in terms of geography, industry, income level, age distribution, morbidity and mortality, thereby making them appropriate for an epidemiological investigation (38).
A total of 2148 pupils were invited to participate in this study, and 1748 pupils and at least one parent/guardian provided informed consent. The population was assessed twice within one 12-month period resulting in 1439 participants at both data collection points. The data collection was carried out as part of the project “Health and Well-being”, which specifically examined the prevalence and effect of a universal preventive programme aimed at reducing social anxiety (39).
Teachers responsible for each class were given instructions on how to distribute consent forms and conduct the assessments. Written information about the study “Health and well-being” and consent forms were distributed to pupils by a teacher during a class session and were taken home to parents/guardians. The questionnaire forms were handed out by a teacher in the classroom and completed in the presence of the teacher. Almost all pupils completed the questionnaires in one session and within the 45-minute period allocated. In addition to the SMFQ, the booklet also included various scales assessing anxiety, stressful life events, resilience and quality of life. The schools in Norway are highly integrated containing severe intellectually and physically handicapped children and adolescents. Six pupils with severe mental retardation and extensive reading comprehension difficulties were excluded from the study.
Measurement
A self-reporting questionnaire was used in this population study. Depressive symptoms were measured by The Short Mood and Feelings Questionnaire (SMFQ) (40, 41). SMFQ is a 13-item self-report questionnaire designed to measure core depressive symptomatology in children and adolescents aged 6–17 years old. SMFQ assesses symptoms of depression during the past 2 weeks. All 13 items are negatively phrased and rated on a 3-point Likert scale with response categories ranging from 0 (Not true) to 2 (True). Example items include “I felt miserable or unhappy”, “I did everything wrong” and “I cried a lot”. Total scores range from 0 to 26, and high sum scores indicate high levels of depression symptomatology. SMFQ has been found to differentiate between depressed adolescents and non-depressed adolescents in the general population (42, 43), and there is good evidence of SMFQ’s psychometric properties such as conceptual validity, convergent validity and reliability (44). The SMFQ is a unifactorial measure with a high reliability score of α = 0.90 in Cronbach’s alpha (45). Cronbach’s alphas for the 13 depression items in this study was (α = 0.88) at assessment point 1 and (α = 0.86) at assessment point 2.
In a large population-based study that surveyed 10,220 adolescents 16–18 years of age, assessing both sleep and depression, the 90th percentile has been used as a cut-off score for SMFQ (46). A 90th percentile in our population is a total score of 10 for SMFQ at assessment point 1. We used a total score of 11 or higher for SMFQ to classify high levels of depressive symptoms and avoid over-reporting.
Ethical consideration
The Regional Committee for Medical and Health Research Ethics approved the re-use of data to investigate depressive symptoms among children and adolescents (REK) 2015/2315. Written information about this new project was sent by regular mail to the participants in the “Health and well-being” survey. The informants were given the opportunity to decline data reuse. One participant gave written feedback expressing that they did not want to attend the new study. All data obtained regarding this written information was deleted.
Data is stored anonymously and separately from identifiable name lists. Consent declarations and name lists are kept secure and locked away in line with recommendations from the Regional Committee for Medical and Health Research Ethics.
Statistics
Statistical analyses were conducted using the SPSS, Version 23.0 software (47). We present the specific point prevalence rates assessed across gender at both assessment points, the 12-month prevalence and 12-month incidence rates. In keeping with previous research, we defined depression cases at 12 months as having an SMFQ score of 11 or greater at each assessment point (48). Moreover, the 12-month incidence rates include those who scored above ≥ 11 at the second but not the first assessment point. Chi-squared analyses were used to investigate potential gender differences in point prevalence, 12-month prevalence and 12-month incidence. Effect sizes are defined as follows: Cramer’s V (49), no effect (0–0.099), low (0.100–0.299), moderate (0.300–0.499) and strong effect (≥0.5) (50). The significance level is set at 5% (51).
Results
A total of 2,148 pupils were invited to the study. A total of 1748 (81.6%) children and adolescents aged 11-14, 892 girls (51%) and 856 boys (49%), participated at assessment point. Further, 1439 participated at both assessment points. The average age of those who participated at both assessment points was 12.6 year (SD=1.09).
Point prevalence
The point prevalence among adolescents aged 11-14 was 9.3% at the first assessment point and 7.9% at the second assessment point. An independent chi-squared analysis confirmed a significant reduction in point prevalence differences between assessment point 1 (9.3%) and assessment point 2 (7.9%), χ2 (1) = 117.180 p < .000. At the first assessment point, 12.2 % of the girls and 6.1 % of the boys reported a high level of depressive symptoms (SMFQ ≥ 11). An independent chi-squared analysis indicated significant gender differences in point prevalence at the first assessment point, χ2 (1) = 15.993 p < .001, Cramer’s V = .106. At the second assessment point, 10.8% of girls and 4.8% of the boys reported high levels of depressive symptoms (SMFQ ≥ 11), and an independent chi-squared analysis revealed significant gender differences χ2 (1) = 17.509 p < .001, Cramer’s V = .110.
TABLE 1.
Point prevalence, 12-month prevalence and 12-month incidence among the total population, and separately among girls and boys at age 11-14 years
| Total | Girls 746 (51.9%) | Boys 691 (48.1 %) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Total | N | % | CI | n | % | CI | n | % | CI |
| Point prev. 1 | 133 | 9.3 | 7.80 - 10.80 | 91 | 12.2 | 9.85 - 14.55 | 42 | 6.1 | 4.31 - 7.89 |
| Point prev. 2 | 113 | 7.9 | 6.50 - 9.30 | 80 | 10.8 | 8.57 - 13.03 | 33 | 4.8 | 3.20 - 6.40 |
| 12-month Prevalence | 42 | 2.9 | 2.03 - 3.77 | 33 | 4.5 | 3.01 - 5.99 | 9 | 1.3 | .45 - 2.15 |
| 12-month Incidence | 69 | 4.8 | 3.69 - 5.92 | 45 | 6.1 | 4.38 -7.82 | 24 | 3.5 | 2.13 - 4.87 |