We provide a systematic review of epidemiological surveys of autistic disorder and pervasive developmental disorders (PDDs) worldwide. A secondary aim was to consider the possible impact of geographic, cultural/ethnic, and socioeconomic factors on prevalence estimates and on clinical presentation of PDD. Based on the evidence reviewed, the median of prevalence estimates of autism spectrum disorders was 62/10 000. While existing estimates are variable, the evidence reviewed does not support differences in PDD prevalence by geographic region nor of a strong impact of ethnic/cultural or socioeconomic factors. However, power to detect such effects is seriously limited in existing data sets, particularly in low‐income countries. While it is clear that prevalence estimates have increased over time and these vary in different neighboring and distant regions, these findings most likely represent broadening of the diagnostic concets, diagnostic switching from other developmental disabilities to PDD, service availability, and awareness of autistic spectrum disorders in both the lay and professional public. The lack of evidence from the majority of the world's population suggests a critical need for further research and capacity building in low‐ and middle‐income countries. Autism Res 2012, 5: 160–179. © 2012 International Society for Autism Research, Wiley Periodicals, Inc.

Two-thirds of ASD cases in the overall sample were in the mainstream school population, undiagnosed and untreated. These findings suggest that rigorous screening and comprehensive population coverage are necessary to produce more accurate ASD prevalence estimates and underscore the need for better detection, assessment, and services.

In order to develop a structured and objective diagnostic instrument, authors completed: (1) the translation and back translation of the Korean version of the Kiddie-Schedule for Affective Disorders and Schizophrenia - Present and Lifetime Version (K-SADS-PL) and (2) the examination of its validity and reliability of the K-SADS-PL-Korean version (K-SADS- PL) when used with Korean children. A total of 91 study subjects were recruited from child and adolescent psychiatry outpatient clinics. Clinical diagnoses were used as a gold standard for the examination of validity of K-SADS-PL-K. Consensual validity of threshold and sub-threshold diagnoses were good to excellent for attention-deficit/hyperactivity disorder (ADHD), fair for tic and oppositional defiant disorders, and poor to fair for anxiety and depressive disorders. Inter-rater and test-retest reliabilities were fair to excellent for ADHD and tic disorder. The significant correlations between the K-SADS-PL-K and Korean Child Behavior Checklist (K-CBCL) were found, which provided additional support for the concurrent validity of the K-SADS-PL-K. Sensitivities varied according to the diagnostic categories, but specificities remained high over all diagnoses, suggesting that the K-SADS-PL-K is a desirable confirmatory diagnostic tool. The results of this study suggest that the K-SADS-PL-K is an effective instrument for diagnosing major child psychiatric disorders, including ADHD, behavioral disorders and tic disorders in Korean children. Future studies will examine the validity and reliability of the K-SADS-PL-K in larger samples, including adolescents and community samples on a variety of child and adolescent psychiatric disorders.

School bullying is highly prevalent in Korean middle school students. Demographic characteristics can help identify students at greater risk for participation in school bullying.

Objective Changes in autism diagnostic criteria found in DSM5 may affect Autism Spectrum Disorder (ASD) prevalence, research findings, diagnostic processes and eligibility for clinical and other services. Utilizing our published, total-population Korean prevalence data, we compute DSM5 ASD and Social Communication Disorder (SCD) prevalence and compare them to DSMIV Pervasive Developmental Disorder (PDD) prevalence estimates. We also describe individuals previously diagnosed with DSMIV PDD when diagnoses change with DSM-5 criteria. Method The target population was all 7-12-year-old children in a South Korean community (N= 55,266), those in regular and special education schools and a disability registry. We utilized the Autism Spectrum Screening Questionnaire for systematic, multi-informant screening. Parents of screen-positive children were offered comprehensive assessments using standardized diagnostic procedures, including the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule. Best estimate clinical diagnoses were made using DSMIV PDD and DSM5 ASD and SCD criteria. Results DSM5 ASD estimated prevalence is 2.20% (CI: 1.77-3.64). Combined DSM-5 ASD and SCD prevalence is virtually same as DSM-IV PDD prevalence (2.64%). Most children with Autistic Disorder (99%), Asperger Disorder (92%), and PDD NOS (63%) met DSM-5 ASD criteria, whereas 1%, 8% and 32%, respectively, met SCD criteria. All remaining children (2% ) had other psychopathology, principally Attention Deficit Hyperactivity Disorder and anxiety disorder. Conclusion Our findings suggest that most individuals with a prior DSMIV PDD meet DSM5 diagnostic criteria for ASD and SCD. PDD, ASD or SCD, extant diagnostic criteria identify a large, clinically meaningful group of individuals and families who require evidence-based services.

While a growing number of studies indicate associations between experiences of bullying and autism spectrum disorder (ASD), it is not clear what roles comorbid behavioral problems may play. We investigated the experiences of children with ASD as victims and/or perpetrators of bullying. Children with ASD epidemiologically ascertained participated in a cross-sectional study. Although children with ASD showed significantly increased risk for bullying involvement compared to community children, after controlling for comorbid psychopathology and other demographic factors, increased risks for being perpetrators or victim-perpetrators disappeared while risk for being bullied/teased continued to be significantly elevated. This finding will help guide medical, educational and community personnel to effectively identify children with ASD at risk for school bullying and develop interventions.

Pre- and perinatal complications have been implicated in the onset and clinical expression of Tourette syndrome albeit with considerable inconsistencies across studies. Also, little is known about their role in co-occurring obsessive-compulsive disorder (OCD) and attention–deficit/hyperactivity disorder (ADHD) in individuals with a tic disorder. Therefore, we aimed to investigate the role of pre- and perinatal complications in relation to the presence and symptom severity of chronic tic disorder and co-occurring OCD and ADHD using data of 1,113 participants from the Tourette International Collaborative Genetics study. This study included 586 participants with a chronic tic disorder and 527 unaffected family controls. We controlled for age and sex differences by creating propensity score matched subsamples for both case-control and within-case analyses. We found that premature birth (OR=1.72) and morning sickness requiring medical attention (OR=2.57) were associated with the presence of a chronic tic disorder. Also, the total number of pre- and perinatal complications was higher in those with a tic disorder (OR=1.07). Furthermore, neonatal complications were related to the presence (OR=1.46) and severity (b=2.27) of co-occurring OCD and also to ADHD severity (b=1.09). Delivery complications were only related to co-occurring OCD (OR=1.49). We conclude that early exposure to adverse situations during pregnancy is related to the presence of chronic tic disorders. Exposure at a later stage, at birth or during the first weeks of life, appears to be associated with co-occurring OCD and ADHD.

Discrepancy in perception of bullying experiences may lead to later internalizing or externalizing behavior in adolescents. A 1,663 South Korean 7th and 8th graders (mean age: 13.1 and 14.1 years old), were seen for a follow‐up study to examine the relationships between the discrepancy in perception of their bullying experiences (defined as discrepancy between self‐ and peer‐reports of bullying experiences) and internalizing or externalizing behavior at follow‐up. Bullying was assessed by self‐ and peer‐report. The discrepancy in perception of bullying experiences was defined by the concordance or discordance between self‐ and peer‐reports. Internalizing and externalizing behavior was evaluated using the Youth Self Report and Child Behavior Checklist, at baseline and follow‐up. Two by two ANCOVA was performed with a factorial design, categorizing discrepancy in perception of bullying experiences based on the agreement between self‐report and peer‐report. Internalizing/externalizing behavior‐at‐follow‐up was used as an outcome, adjusting for other known risk factors for internalizing/externalizing behavior, including baseline internalizing/externalizing behavior, and bullying experiences. Adolescents with perceptions of bullying experiences discrepant from peer‐reports showed increased internalizing/externalizing behavior at follow‐up. Bullying also stands out as an independent risk factor for the development of future externalizing behavior even among adolescents with accurate perceptions of bullying experiences. These specific groups of youth warrant more focused assessment and intervention.