This study highlights a significant overall increase in the incidence of all mental health diagnoses during the COVID-19 pandemic, with anxiety disorders being the most common. Notably, the incidence of all studied mental health disorders was higher in girls compared to boys, with the exception of ADHD. Additionally, there was an elevated incidence of depression and anxiety diagnoses among individuals aged 19-24 years, while ADHD was more prevalent in the younger cohort aged 10-14 years. Depressive and anxiety disorders were more common among individuals from the most deprived areas, whereas eating disorders and ADHD were more frequent among those from less deprived areas. Furthermore, the incidence of mental health disorders was generally lower among individuals of non-Spanish nationality compared to Spanish nationals.
We noticed a consistent increase in incident depressive and anxiety disorders from 2008 to 2022, which is consistent with the results from longitudinal studies conducted in the UK [13] as well as a previous study carried out in Catalonia that used a different database [12]. Recent reviews corroborate the ongoing secular increase in the incidence of mental health disorders in adolescents, particularly in high-income countries, which is plateauing globally [24].
We observed increases in the incidence of all disorders in the years 2011-2013. This phenomenon, which has already been documented both in Catalonia [12] and in the UK [13], may be related to the impact of the economic crisis that began in 2008 [25]. The crisis reached its peak social impact in Spain in 2011 and continued in the following years due to austerity policies affecting social welfare, health, and education. [26].
Nevertheless, in this study a sharp increase in incidence of studied mental health disorders was noted following the onset of the COVID-19 pandemic. In 2020, a temporary dip in the incidence curves of anxiety, depression, and ADHD is observed. This finding aligns with other epidemiological studies on mental health disorders [27, 28] and can be attributed to the lockdown and restrictions on access to healthcare services during the early months of the COVID-19 pandemic [29, 30]. Longitudinal studies that calculated the incidence rates of mental health disorders over shorter periods (monthly or bimonthly) show a notable decrease in new recorded diagnoses in the initial months after the outbreak, with a gradual return thereafter to expected values [27, 28]. Following this decline, there has been a dramatic increase in all studied disorders until 2022. This surge reflects the adverse effects on adolescent and youth mental health resulting from the pandemic, as well as that of the lockdown and social distancing measures that were implemented. These impacts have been observed using different methodologies in many countries around the world [14].
Anxiety was the most frequent diagnosis during our study period, with incidences 5-times that of depression or about 10-times that of ADHD or eating disorders. While the higher prevalence of anxiety disorders compared to other disorders is expected, it appears excessively disproportionate considering epidemiological data [31]. Anxiety symptoms can be part of the clinical expression of other mental disorders or can precede the manifestation of other symptoms or mental health disorders [32]. Therefore, a significant percentage of the diagnoses of anxiety registered in primary care records may be an indicator of nonspecific emotional distress or preliminary states of other disorders.
The results of this study reveal a worsened state of mental health among girls, with a higher incidence in all disorders except ADHD. This disparity may be partly attributed to a sexist social system, where sexism and other forms of violence against women negatively impact mental health [7, 33]. Additionally, the greater prevalence of diagnoses in girls could be linked to the gender socialization process, which may enhance girls' ability to express psychological discomfort [33]. The results suggest that psychological distress manifests differently by gender, with girls more likely to express it emotionally, while boys tend to express it behaviorally [33]. This would correspond to the higher incidence in girls of depressive, anxiety, and eating disorders, and in boys of ADHD. ADHD incidence is consistently higher in boys than in girls throughout the study period, which could be attributed to sex bias in its clinical diagnosis process: girls with ADHD may be more easily overlooked due to a higher symptom threshold requirement for seeking help and diagnosis [34].
For eating disorders, the results reveal higher incidence in girls than in boys, in line with many other studies which indicate a greater presence of these disorders in girls [35]. This may be due to gender norms related to body image and weight [36] though other research suggests these disorders express different cultural norms, values, and conflicts influenced by gender and the sociocultural context [37].
According to age, our findings are consistent with the idea that internalized symptoms are more prevalent in older adolescents and young adults, whereas externalized symptoms are more prevalent in children and adolescents [38]. Thus, the 15-18 and 19-24 age groups would score higher for depressive and anxiety disorders, while the 10 -14 age group would score higher for ADHD. Age is a determining factor in the incidence of ADHD, displaying a gradient: the incidence is higher in the younger age group (10-14 years) while new ADHD diagnoses are infrequent in the age group over 18 years old. A limitation of our data is that we did not examine individuals under the age of 10, when, according to epidemiological data, the peak incidence by age is precisely around 7-9 years old [39].
Our study also observed a noteworthy relationship between socioeconomic deprivation and the incidence of ADHD and eating disorders, which diverges from patterns seen in other disorders. While depressive and anxiety disorders show higher incidence among individuals in the most deprived groups, ADHD presents higher incidence among individuals in the least deprived groups. This contradicts findings where ADHD symptoms, diagnoses, and treatments were more among individuals in most deprived groups [39, 40, 41]. Other studies reveal the mechanisms of more frequent ADHD diagnoses among individuals in diagnoses in individuals of high socioeconomic status, including heightened awareness among parents and teachers, greater academic performance expectations, higher health literacy, and improved access to healthcare [42, 43]. Moreover, the DSM-5 expanded the criteria for ADHD diagnosis, which may partially explain the peak in diagnoses around 2013.
Similarly, eating disorders predominantly occur in least deprived group. The reasons remain unclear, though some studies suggest that in statistical terms, a high family level of education is a risk factor. The relation between socioeconomic-status and higher incidence of eating disorders should continue to be studied [44].
Our study surprisingly revealed lower incidence of the studied mental health disorders among non-Spanish nationals compared to those with Spanish nationality. Despite universal coverage offered by the Spanish public healthcare system, barriers related to language and culture, lack of familiarity with rights, gaps in health literacy, limited knowledge of the health system, discrimination, and socioeconomic inequity lead to differential treatment within the healthcare system [45]. However, those of American nationality have shown a strong and sustained increase in the incidence of depression and anxiety since 2015, accelerating from the outbreak of the COVID-19 pandemic, resulting in their rates surpassing those of individuals with Spanish nationality. The specific factors behind these differential incidence trends merit further research.
There is a significant issue of psychological distress and adverse mental health among adolescents and young people, which have been exacerbated by the COVID-19 pandemic, though they preceded it [24]. Structural factors, discrimination and violence are risk factors, as they are different expressions of psychological distress between genders, age groups and socioeconomic status [7, 33, 37, 38]. Parental psychopathology, living in an urban context, excessive use of the internet and social networks, among others, have been identified as risk factors in previous research [46, 47], mediated by additional factors that facilitate or promote seeking help in the healthcare system [48]. Understanding this phenomenon is necessary for an appropriate response from the healthcare system and, since many relevant determinants are not healthcare-related, the response must also be rooted in societal change [49].
This study has limitations that must be considered when interpreting the results. Firstly, the data pertain to diagnoses recorded in primary care medical records, not the actual incidence of mental disorders in the population. Underdiagnosis or overdiagnosis can contribute to discrepancies between recorded diagnoses and the actual presence of disorders in the population [43, 50]. Additionally, increased knowledge and awareness among physicians and pediatricians about mental disorders, decreased stigma, and social trends regarding mental health, can facilitate increased help-seeking behavior and mental health diagnoses [51]. Secondly, diagnoses given in specialized psychiatry settings may not be adequately recorded in primary care medical records. However, within the Catalan public health system, primary and specialty care are integrated, reducing underreporting [52]. The management of chronic diagnoses initiated in other levels of care, –including private healthcare–, usually occur in primary care [53], reducing the probability of undocumented diagnostic information. Thirdly, for the gender-based analysis, we used the variable "sex" as a proxy. However, we acknowledge that gender is a far more complex construct that cannot be limited to a simple binary biological category [54]. And finally, the variable "nationality" must be interpreted with caution since we lack other data regarding origin, years of residence in the country, level of integration, or other relevant factors [55].
The strengths of the study lie in the sample size and the use of real-world origin of the data. Our study reports broadly representative data, including about two million adolescents and young adults seen in primary care in Catalonia. The SIDIAP database has been proven to be a valid and useful tool for research purposes [21]. Moreover, the extended study period allows us to analyze and interpret the situation within the context of the COVID-19 pandemic from a temporal perspective, including the secular evolution of the outcomes of interest since 2008. Additionally, our study encompasses the entire period of the COVID-19 pandemic, from its onset in early 2020 to the end of 2022, shortly before the formal declaration of the end of the pandemic by the WHO in March 2023 [56].