From temperament to YouTube: exploring the link between childhood temperament, YouTube usage patterns, and emotional/behavioral problems among children.

BACKGROUND: YouTube is a widely used video sharing and social networking platform among children and adolescents. However, research on YouTube usage among this population remains scarce. Specifically, studies on factors that influence children and adolescents' usage are clinically significant but largely lacking. Additionally, few studies have examined the association between usage and emotional/behavioral problems, which is fundamental to smartphone research. Therefore, this study explored the relationship between early childhood temperament, subsequent YouTube usage patterns, and emotional/behavioral problems. METHODS: The Kids Cohort for Understanding Internet Addiction Risk Factors in Early Childhood (K-CURE) is the first long-term prospective cohort study in Korea aimed at understanding the long-term effects of media exposure on young children. The study included 195 children aged 8-11 years enrolled in the K-CURE study. Caregivers, predominantly mothers, who voluntarily participated during their visits to community centers for children's mental health in Korea's major cities, completed a detailed self-administered survey. Childhood temperament was measured in 2018 when the children were 5-8 years old. Subsequent YouTube usage patterns and emotional/behavioral problems were assessed in 2021. Data were analyzed using frequency analysis, correlation analysis, and multiple linear regression. RESULTS: The study found that 21.0% of children started using YouTube before age 4, with the most common onset age being 8-9 years (30.3%). These children used YouTube on average 4.8 days per week for 68.5 min per day. Early childhood persistence was negatively associated with the subsequent YouTube usage duration, and the age at first YouTube use was negatively correlated with subsequent usage frequency. Furthermore, a younger age at first YouTube use and higher usage frequency were significantly associated with increased emotional/behavioral problems. CONCLUSIONS: In the YouTube environment, where content is automatically recommended based on user preferences, traits related to usage patterns may be associated with persistence, which is linked to self-regulation. Considering the current trend where children use smartphones, contents frequently for very short durations, our findings highlight the importance of self-regulation in the media usage of children who are still developing. Additionally, our results provide fundamental information for future YouTube studies and illustrate similarities and differences between smartphone and YouTube research.

Safety outcomes of selective serotonin reuptake inhibitors in adolescent attention-deficit/hyperactivity disorder with comorbid depression: the ASSURE study.

BACKGROUND: Attention deficit-hyperactivity disorder (ADHD) is related to depressive disorder, and adolescents with both present poor outcomes. However, evidence for the safety of concomitantly using a methylphenidate (MPH) and a selective serotonin reuptake inhibitor (SSRI) among adolescent ADHD patients is limited, a literature gap aimed to address through this investigation. METHODS: We conducted a new-user cohort study using a nationwide claims database in South Korea. We identified a study population as adolescents who were diagnosed both ADHD and depressive disorder. MPH-only users were compared with patients who prescribed both a SSRI and a MPH. Fluoxetine and escitalopram users were also compared to find a preferable treatment option. Thirteen outcomes including neuropsychiatric, gastrointestinal, and other events were assessed, taking respiratory tract infection as a negative control outcome. We matched the study groups using a propensity score and used the Cox proportional hazard model to calculate the hazard ratio. Subgroup and sensitivity analyses were conducted in various epidemiologic settings. RESULTS: The risks of all the outcomes between the MPH-only and SSRI groups were not significantly different. Regarding SSRI ingredients, the risk of tic disorder was significantly lower in the fluoxetine group than the escitalopram group [HR 0.43 (0.25-0.71)]. However, there was no significant difference in other outcomes between the fluoxetine and escitalopram groups. CONCLUSION: The concomitant use of MPHs and SSRIs showed generally safe profiles in adolescent ADHD patients with depression. Most of the differences between fluoxetine and escitalopram, except those concerning tic disorder, were not significant.

Relationship between screen time among children and lower economic status during elementary school closures due to the coronavirus disease 2019 pandemic.

BACKGROUND: This study aimed to examine whether the extended use of a variety of digital screen devices was associated with lower economic status and other environmental factors among Korean elementary school children and their caregivers during school closures precipitated by the coronavirus disease 2019 (COVID-19) pandemic. METHODS: A total of 217 caregivers of children 7-12 years of age from Suwon, Korea, were recruited and asked to respond to a self-administered questionnaire in June 2020. The questionnaire addressed demographic information and children's use of digital media, in addition to their caregivers. The t-test was used for continuous variables, and the Kruskal-Wallis test was used for variables measured on an interval scale. A multiple regression analyses were performed to examine the effects of significant correlative factors on screen time in children as predictors. RESULTS: Children with lower household incomes demonstrated a higher frequency and longer duration of smartphone and tablet personal computer use compared to those from higher income households. Children of households in which incomes decreased after COVID-19 used smartphones and tablet PCs more often and for longer durations. Children from households that experienced decreased income(s) after COVID-19 used personal computers more often and for a longer duration, and children from low-income families engaged in longer screen time on smartphones. A change in primary caregiver(s) may have increased children's screen time on smartphones. CONCLUSION: Lower household income was associated with longer screen time among children, and poor mental health among caregivers during school closures precipitated the COVID-19 pandemic.

Lower-Income Predicts Increased Smartphone Use and Problematic Behaviors Among Schoolchildren During COVID-19 Related School Modification: A Longitudinal Study.

BACKGROUND: As the coronavirus disease 2019 (COVID-19) has continued for a couple of years, the long-term effects of the pandemic and the subsequent school curriculum modification on the mental health of children and parents need to be investigated. To clarify the changes that can occur during one school year and to predict the risk factors for vulnerable groups, this study identified parameters relative to children's screen time, their problematic behavior, and parental depression. METHODS: A total of 186 participants were analyzed who were parents of elementary schoolchildren in South Korea. These parents were required to complete a web-based questionnaire twice. The questionnaires were conducted in June 2020 and September 2021. Participants' general demographics including family income, children's screen time, sleep patterns, problematic behavior, and parental depression were assessed via the parental questionnaire that included various measurement tools. RESULTS: Children's body mass index (BMI) increased significantly in 2021 (18.94 ± 3.75 vs. 18.14 ± 3.30, P < 0.001). Smartphone frequency of use per week (5.35 vs. 4.54, P < 0.001) and screen time per day (3.52 vs. 3.16, P < 0.001) significantly increased during the period of the COVID-19 pandemic. The television screen time (2.88 vs. 3.26, P < 0.001), frequency of viewing (3.77 vs. 4.77, P < 0.001), and children's problematic behaviors significantly decreased (9.15 vs. 11.85, P < 0.001). A lower income household was a key predictor of increased smartphone frequency (B = 1.840, 95% confidence interval [CI], 0.923-2.757, P < 0.001) and smartphone screen time (B = 1.992, 95% CI, 1.458-2.525, P < 0.001). The results showed that the lower income household (B = 5.624, 95% CI, 2.927-8.320, P < 0.001) and a child's psychiatric treatment history (B = 7.579, 95% CI, 5.666-9.492, P < 0.001) was the most significant predictor of problematic behaviors of children and parental depression (B = 3.476, 95% CI, 1.628-5.325, P < 0.001; B = 3.138, 95% CI, 1.827-4.450, P < 0.001). CONCLUSION: This study suggested that children's smartphone screen time and BMI increased during COVID-19 because of the school curriculum modification following school closures in South Korea. The increased children's problematic behaviors and parental depression were predicted by lower-income households and the previous psychiatric history of children. These results indicate that multiple social support systems to the vulnerable group are needed during the ongoing pandemic and that a modified school setting is required.

Parental Mental Health and Children's Behaviors and Media Usage during COVID-19-Related School Closures.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is different from previous disasters in that it continues to the present and has affected all aspects of family life. During epidemics, psychosocial support is not less important than infection control. During COVID-19-related school closures, prolonged partial closures of schools could have detrimental social and health consequences for children and may increase the burden on the family. Based on a community sample in Korea, this study identified parental concerns, children's media usage, other various factors and examined whether parental stress level or depression were positively associated with problem behaviors, media exposure, and sleep problems of the primary school children during school closure under COVID-19. METHODS: Participants were 217 parents residing in Suwon, South Korea, who had primary school children and responded to a web-based questionnaire on parental concerns from school closure under COVID-19, subjective stress, depression, whether having received mental health services, and family characteristics; children's sleep patterns, problem behaviors, media usage during the online-only class period, and changes in activity level following the pandemic. RESULTS: During school closure, children gained body weight, spent less time in physical activities and more in media usage. Besides online learning content (97.2%), YouTube was highly used content (87.6%), and games followed (78.3%). Parental subjective stress index was highly associated with parental depression (Pearson correlation 0.439, P < 0.001), children's sleep problems (0.283, P < 0.001), tablet time (0.171, P = 0.012) and behavior problems (0.413, P < 0.001). Parental depression was associated with children's sleep problems (0.355, P < 0.001), TV time (0.153, P = 0.024), tablet time (0.159, P = 0.019), and behavior problems (0.524, P < 0.001). Parents who previously received mental services seemed to be more concerned about the problems their children already have getting worse because of COVID-19 than the disease itself. Children's sleep problem was associated with tablet (0.172, P = 0.011) and smartphone time (0.298, P < 0.001), but not its frequency. CONCLUSION: During COVID-19-related school closures, many parents and children had various difficulties relating to mental health. Ongoing monitoring of mental health of high-risk groups and multiple support systems may need to be expanded to cover those parents having difficulty in caring for their children.

Trends in Digital Media Use in Korean Preschool Children.

BACKGROUND: Children today are exposed to various media devices, and their usage of these is increasing. Prior studies have outlined forms of harm this can potentially cause. However, there has been little empirical research on the use of media devices among preschool children in Asia. The aim of this study was to examine and analyze longitudinal trends in media device use among Korean preschool children, focusing on the frequency of engagement, time spent with, and ownership of media devices, delineated by sex. METHODS: Four hundred parents of children aged 2-5 years were invited to enroll. The baseline assessment, Wave 1, was conducted between December 2015 and June 2016, and follow-up assessments, Wave 2 and Wave 3, were conducted annually for the following 2 years. Time of media use, frequency of media use, and ownership of media devices (TV, tablet PCs, and smartphones) were investigated. RESULTS: Ownership of tablet PCs increased significantly between Wave 1 and Wave 3 for boys and girls (corrected P < 0.001). Frequency of media use increased significantly between Wave 1 and Wave 3 only in boys' use of tablet PCs (mean difference 0.8 day/wk). Time of media use increased significantly between Wave 1 and Wave 3 for both sexes in all devices, measured by mean difference on weekdays and weekends (TV by 0.6 and 0.7 hr/day, tablet PCs by 0.6 and 0.8 hr/day, and smartphones by 0.4 and 0.4 hr/day). Children spent more time using media devices during weekends than on weekdays. CONCLUSION: This study observed an increase in the tendency of media device use among preschool children in Korea. The patterns of use indicate that paying attention to the types of devices children use is needed, as well as vigilance on weekends.

Maternal Depression and Children's Screen Overuse.

BACKGROUND: It is known that there are various factors associated with children's screen overuse. The aim of this study was to examine the effect of maternal depression on 2-5-year-old children's overuse of various household screen devices. METHODS: Participants were from the Internet-Cohort for Understanding of internet addiction Risk factors/Rescue in Early livelihood (I-CURE) study, an observational prospective cohort study in Korea. Screen time for six types of screen devices (smartphone, television, computer, tablet, video gaming console, and portable gaming console) were assessed by parental questionnaire. Maternal depression was measured by the Korean version of the Beck Depression Inventory II. Logistic regression models were run to determine the association between maternal depression and children's screen overuse. RESULTS: Maternal depression was associated with children's television overuse after adjusting for other factors (odds ratio, 1.954; P = 0.034). Contrary to expectation, the relationship between maternal depression and screen time was not present on other devices such as smartphones, computers and tablets. CONCLUSION: Maternal depression is related with 2-5-year-old children's television overuse. Interventions in maternal depressive symptoms and the associated changes in parent-child relationship can be useful for preventing children's television overuse.

The effects of maternal depression on child mental health problems based on gender of the child.

Depression is a common disorder among women with young children. Compared to non-depressed mothers, depressed mothers tend to display less positive affection, provide less emotional support, and inconsistently respond to their child's every day and emotional needs. We examined the association between maternal depression and child (middle childhood) mental health problems according to the child's gender. This study was conducted between June and August 2006 on 3,911 subjects aged 7-12 years. The data for this study was collected through a questionnaire that included the Beck Depression Inventory (BDI) and Korean Child Behavior Checklist (K-CBCL). Most of the CBCL scores were higher for children in the depressed mother group. The two way ANOVAs (depressed group by gender) found girls to have significantly higher scores than boys on somatization. Children may experience somatic complaints when they also suffer from emotional disorders, and therefore must be observed closely.

Factor structure of the Internet Addiction Scale and its associations with psychiatric symptoms for Korean adolescents.

In this paper, we explore underlying factors of Internet Addiction Scale (IAS) and examine how the dimensions of the IAS relate to psychiatric symptoms in Korean adolescents. Exploratory factor analysis with a sample of N = 1,722 consisted of 13-15 year old Korean adolescents identified three distinctive factors of IAS and they were labeled 'time management', 'withdrawal behaviors' and 'neglect work'. Then, multiple regression models were applied to assess the association between each factor and eight psychological problems, which were evaluated by Youth Self Report. The overall IAS was significantly associated with Somatic, Immature, Thought, Attention, Delinquent and Aggressive behaviors. However, three factor scores showed different association patterns and indicated multidimensional aspects of problematic Internet use.

Norepinephrine genes predict response time variability and methylphenidate-induced changes in neuropsychological function in attention deficit hyperactivity disorder.

Noradrenergic dysfunction may be associated with cognitive impairments in attention-deficit/hyperactivity disorder (ADHD), including increased response time variability, which has been proposed as a leading endophenotype for ADHD. The aim of this study was to examine the relationship between polymorphisms in the α-2A-adrenergic receptor (ADRA2A) and norepinephrine transporter (SLC6A2) genes and attentional performance in ADHD children before and after pharmacological treatment.One hundred one medication-naive ADHD children were included. All subjects were administered methylphenidate (MPH)-OROS for 12 weeks. The subjects underwent a computerized comprehensive attention test to measure the response time variability at baseline before MPH treatment and after 12 weeks. Additive regression analyses controlling for ADHD symptom severity, age, sex, IQ, and final dose of MPH examined the association between response time variability on the comprehensive attention test measures and allelic variations in single-nucleotide polymorphisms of the ADRA2A and SLC6A2 before and after MPH treatment.Increasing possession of an A allele at the G1287A polymorphism of SLC6A2 was significantly related to heightened response time variability at baseline in the sustained (P = 2.0 × 10) and auditory selective attention (P = 1.0 × 10) tasks. Response time variability at baseline increased additively with possession of the T allele at the DraI polymorphism of the ADRA2A gene in the auditory selective attention task (P = 2.0 × 10). After medication, increasing possession of a G allele at the MspI polymorphism of the ADRA2A gene was associated with increased MPH-related change in response time variability in the flanker task (P = 1.0 × 10).Our study suggested an association between norepinephrine gene variants and response time variability measured at baseline and after MPH treatment in children with ADHD. Our results add to a growing body of evidence, suggesting that response time variability is a viable endophenotype for ADHD and suggesting its utility as a surrogate end point for measuring stimulant response in pharmacogenetic studies.

Does psychopathology in childhood predict internet addiction in male adolescents?

This study investigated childhood psychopathology and Internet addiction in adolescents. Initial assessment data were obtained from 1998 to 1999, and a follow-up assessment was performed in 2006, when the original subjects entered middle school. Personal information for the 524 male subjects was obtained from the original data. The subjects were evaluated with the Korean version of the child behavior checklist, which was administered to the children's parents. Demographic and psychosocial factors were also evaluated. Children were reassessed with the self-reported Korea Internet Addiction Scale. Our results indicated that 3.6 % of the subjects had Internet addiction, and revealed a significant relationship between withdrawal and anxiety/depression and future Internet addiction. The results suggest that withdrawal and anxiety/depression during childhood should be considered in the etiology of problematic Internet use in boys. Accordingly, clinicians should consider anxiety/depression and withdrawal during childhood to prevent Internet addiction.

Effects of Screen Time on Problematic Behavior in Children During the COVID-19 Pandemic in South Korea.

Objectives: The coronavirus disease 2019 (COVID-19) pandemic has led to a decrease in face-to-face classes worldwide, affecting the mental health of children and their parents. The global pandemic has increased children's overall use of electronic media. This study analyzed the effect of children's screen time on problematic behaviors during the COVID-19 pandemic. Methods: A total of 186 parents from Suwon, South Korea, were recruited to participate in an online survey. The mean age of the children was 10.14 years old, and 44.1% were females. The questionnaire included questions on children's screen time, problematic behaviors, and parental stress. Children's behavioral problems were evaluated using the Behavior Problem Index, whereas the Parental Stress Scale was used to estimate parental stress. Results: The mean smartphone usage frequency of the children was 5.35 days per week, and the mean smartphone screen time was 3.52 hours per day. Smartphone screen time (Z=4.49, p <0.001) and usage frequency (Z=2.75, p=0.006) were significantly correlated with children's behavioral problem scores. The indirect effect of parental stress on this relationship was also statistically significant (p=0.049, p=0.045, respectively). Conclusion: This study suggests that children's smartphone screen time has affected problematic behaviors during the COVID-19 pandemic. Furthermore, parental stress is related to the relationship between children's screen time and problematic behaviors.

Validation of the Korean self-administered computerized versions of the kiddie schedule for affective disorders and schizophrenia for school-age children (KSADS-COMP).

The purpose of the present study was to examine the validity of the Korean version of the parent and youth self-administered versions of the KSADS-COMP (The Kiddie Schedule for Affective Disorders and Schizophrenia for school-age children). To assess the criterion validity of the KSADS-COMP, diagnoses made by the selfadministered KSADS-COMP were compared to the gold-standard diagnoses made by the child-adolescent psychiatrists in 41 participants (mean age=14.93 ± 2.16 years, female=41.46 %). Gwet's first order agreement coefficient (AC1) concordance ratings showed moderate to good range. The present study shows promising validity of the Korean self-administered versions of the KSADS-COMP in Korean youths.

Computerized Version of the Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children (KSADS-COMP): Development and Validation of the Korean Clinician-Administered Version.

OBJECTIVE: The purpose of the present study was to develop and validate the Korean version of the clinician-administered KSADSCOMP, which is the recently updated, web-based computerized version of the Kiddie Schedule for Affective Disorders and Schizophrenia for school-age children (KSADS). METHODS: A total of 71 participants (mean age=12.04±3.86 years, female=29.57%) participated in the study. A child-adolescent psychiatrist established a diagnosis for the participant after a thorough psychiatric interview with the participant and the parent. Researchers who were blind to the diagnoses administered the clinician-administered KSADS-COMP to the parents and participants. The gold-standard diagnoses made by child-adolescent psychiatrists were compared to the current diagnoses generated by the clinician-administered KSADS-COMP. Percent agreement, Cohen's Kappa, Gwet's first-order agreement coefficient (AC1), sensitivity, specificity, positive predictive value, and negative predictive value were calculated. RESULTS: Gwet's AC1, our preferred measure of agreement, showed excellent range between 0.78 and 1. Sensitivity, specificity, positive predicted value and negative predictive value also showed high scores. CONCLUSION: The current study demonstrated excellent criterion validity of the Korean version of the clinician-administered KSADSCOMP, though the small sample size could be a limitation. The current study was the first study to examine the criterion validity of the KSADS-COMP. Due to its readily usable format and efficient and accurate diagnostic process, widely-use of KSADS-COMP is expected.

Use of eye tracking to improve the identification of attention-deficit/hyperactivity disorder in children.

Attention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder of childhood. Although it requires timely detection and intervention, existing continuous performance tests (CPTs) have limited efficacy. Research suggests that eye movement could offer important diagnostic information for ADHD. This study aimed to compare the performance of eye-tracking with that of CPTs, both alone and in combination, and to evaluate the effect of medication on eye movement and CPT outcomes. We recruited participants into an ADHD group and a healthy control group between July 2021 and March 2022 from among children aged 6-10 years (n = 30 per group). The integration of eye-tracking with CPTs produced higher values for the area under the receiver operating characteristic (AUC, 0.889) compared with using CPTs only (AUC, 0.769) for identifying patients with ADHD. The use of eye-tracking alone showed higher performance compare with the use of CPTs alone (AUC of EYE: 0.856, AUC of CPT: 0.769, p = 0.029). Follow-up analysis revealed that most eye-tracking and CPT indicators improved significantly after taking an ADHD medication. The use of eye movement scales could be used to differentiate children with ADHD, with the possibility that integrating eye movement scales and CPTs could improve diagnostic precision.

The pathway of internalizing and externalizing problems from childhood to adolescence: a prospective study from age 7 to 14-16 in Korea.

This study prospectively investigated developmental psychopathology pathway from the age of 7 to ages 14-16. The subjects (N = 1,857) were evaluated using the Korean version of the Child Behavior Checklist and reassessed using the Korean Youth Self Report. In path analyses, total problems, externalizing problems, and internalizing problems in childhood associated significantly with problems in adolescence. In particular, childhood externalizing problems associated with adolescent externalizing problems, for both genders. However, our results differ from those of previous studies in that internalizing problems showed a restrictive stability by gender and in that early externalizing problems correlated negatively with later internalizing problems for girls. In the syndrome scales analyses, we confirmed that some syndromes showed heterotypic pathways, despite the general continuity of the developmental psychopathology. The importance of Anxiety/Depression and Attention problems in childhood suggested that adolescent difficulties are a consequence of an accumulation of such risk factors.

Effects of Frequent Smartphone Use on Sleep Problems in Children under 7 Years of Age in Korea: A 4-Year Longitudinal Study.

The use of electronic screen devices has a negative effect on sleep. The purpose of this study is to longitudinally examine the effects of various screen use on sleep problems in children under 7 years of age. A total of 314 caregivers of children aged 4−7 years from three cities in Korea were recruited and responded to a self-administered questionnaire from 2017 to 2020. As a result of the analysis of the mixed model designed as a two-leveled structure, the use frequency of smartphones significantly predicted children's sleep problems (ß = 0.328, p < 0.001) compared to that of TV, PC, and tablet PC. In addition, the frequency of smartphone screen use showed a weak but significant correlation with bedtime resistance (r = 0.067, p = 0.009), sleep duration (r = 0.089, p <0.001), nighttime awakening (r = 0.066, p = 0.010), and daytime sleepiness (r = 0.102, p < 0.001). The results of this study suggest that screen time education in Korea should focus on smartphones above all else.

Psychiatric disorders among children with acute lymphoblastic leukemia in South Korea: a nationwide population-based longitudinal study.

OBJECTIVE: Children with acute lymphoblastic leukemia (ALL) may be at increased risk of psychiatric disorders. This study analyzed the incidence of psychiatric disorders in children with ALL in South Korea. METHODS: Using nationwide claims data for January 2009 to March 2016, we identified three major psychiatric disorders (depression, anxiety and stress/adjustment disorder) among children diagnosed with ALL. We analyzed the incidence of psychiatric disorders before and after ALL diagnosis. RESULTS: Overall, 2160 children diagnosed with ALL were identified. Seventy-five children (3.5%) were diagnosed with at least one major psychiatric disorder from 1 year before ALL diagnosis to the last follow-up point (range: 42.5-111.5 months). Of these, 70 (93.3%) patients were identified after ALL diagnosis, with the incidence peaking 1 year after ALL diagnosis. Depression, anxiety and stress/adjustment disorders were diagnosed in 30 (1.4%), 15 (0.7%) and 30 (1.4%) patients, respectively. CONCLUSIONS: Among pediatric patients with ALL, most psychiatric disorders were identified after the diagnosis of leukemia, and psychiatric disorder incidence differed according to patient age and time since ALL diagnosis. Timely screening for and proper management of mental disorders are needed during all stages of ALL treatment.

Long-term methylphenidate use for children and adolescents with attention deficit hyperactivity disorder and risk for depression, conduct disorder, and psychotic disorder: a nationwide longitudinal cohort study in South Korea.

BACKGROUND: Methylphenidate (MPH) is the most frequently prescribed medication for the treatment of attention deficit hyperactivity disorder (ADHD). However, the safety of its long-term use remain unclear. In particular, real-world evidence of long-term MPH treatment regarding the risk of depression, conduct disorders, and psychotic disorders in children and adolescents is needed. This study aimed to compare the risks of depression, conduct disorder, and psychotic disorder between long- and short-term MPH treatments in children and adolescents. METHODS: This population-based cohort study used a nationwide claims database of all patients with ADHD in South Korea. Patients aged less than 18 years who were prescribed MPH were included in the study. Long- and short-term MPH were defined as > 1 year, and < 1 year, respectively. Overall, the risk of developing depressive disorder, conduct disorder and oppositional defiant disorder (ODD), and psychotic disorder were investigated. A 1:2 propensity score matching was used to balance the cohorts, and the Cox proportional hazards model was used to evaluate the safety of MPH. RESULTS: We identified 1309 long-term and 2199 short-term MPH users. Long-term MPH use was associated with a significantly lower risk of depressive (hazard ratio [HR], 0.70 [95% confidence interval [CI] 0.55-0.88]) and conduct disorders and ODD (HR, 0.52 [95% CI 0.38-0.73]) than short-term MPH use. Psychotic disorder was not significantly associated with long-term MPH use (hazard ratio [HR], 0.83 [95% confidence interval [CI] 0.52-1.32]). CONCLUSIONS: Our findings suggest that long-term MPH use may be associated with a decreased risk of depression, conduct disorders and ODD. Moreover, the long-term use of MPH does not increase the risk of psychotic disorders. Long-term MPH administration may be considered as a favourable treatment strategy for children and adolescents with ADHD regarding depressive, conduct, and psychotic disorders.