The incidence rate of developmental regression is gradually increasing. In the early stages of children's development, both ASD and DD patients can experience developmental regression, which in turn aggravates cognitive function impairment and seriously affects the effectiveness of intervention and treatment. However, the mechanism is unclear, and early screening and diagnosis are difficult. At present, the etiological mechanism of regressive autism and retardation patients at home and abroad is still unclear.This study will advance knowledge about the biological neurocognitive processes, clinical course and outcomes with the potential to improve child and family outcomes through earlier recognition and support. Based on the previous research foundation and advantages of team members, this young innovation team intends to further improve early disease screening, diagnosis strategies, and scientific typing plans by conducting basic and clinical collaborative research on the pathogenesis, precise typing biomarkers, and intervention treatment targets of children with major developmental regression related diseases, and to search for possible gene and drug intervention targets.

1. Procedures. Children who visited the Children's Health Department between 2021.12 and 2024.12., met the inclusion criteria, and had informed consent signed by their parents. Developmental assessment (Gesell assessment, ABC scale) was routinely performed upon enrollment. After enrollment, routine follow-up visits will be conducted every three months for 1-2 hours each time. Clinicians and researchers will carefully sort out the subject's development process, record and evaluate it. If regression occurs, retest developmental assessment (Gesell assessment, ABC questionnaire). Behavioral assessments and blood samples will be collected once for those found to be regressed upon enrollment. The team will conduct biomarker, genomics, and imaging research based on a prospective patient study cohort.
2. Sample size.This study is a observational trial. 100 children with autism spectrum disorder who met the inclusion criteria and signed informed consent forms were included. Among them, there are 30 cases of children with regressive autism spectrum disorder. 100 children with global developmental delay who met the inclusion criteria and signed informed consent forms were included. Among them, there are 30 cases of children with global developmental delay.And 100 normally developing children. Tools used in the research process: (Gesell assessment, ABC questionnaire).
3. Statistical analysis.All the data are analyzed using SPSS 25.0 or R language,which enters by a dedicated person,and checks by three people to ensure accurate data entry.Statistical analysis is completed under the guidance of professional statistical analysts from the Epidemiology Research Office of the project leader's unit.
4. Ethical matters and data protection. Before epidemiological survey,children and guardians participating in the study signed a consent form and schools signed a disclaimer.During the study,medical ethics laws and regulations were strictly observed,and psychiatrists,psychologists and pediatricians participated in the entire process to provide health protection for children.And they protect the privacy of subjects and do not disclose subjects' information.

Inclusion Criteria:

• （1）ASD patients：

  1. Patients diagnosed with autism spectrum disorder based on DSM-5 by 2 child care physicians and/or psychiatrists with associate senior professional titles or above.
  2. Aged 1-7years

• （2）DDpatients：

  1. Patients diagnosed with global developmental delay based on DSM-5 by 2 child care physicians and/or psychiatrists with associate senior professional titles or above.
  2. Aged 1-7 years

Exclusion Criteria:

• Exclude other histories of mental illness, neurological diseases and severe physical diseases, exclude patients with a history of substance and drug abuse, and patients who have not taken risperidone and other related antipsychotic drugs.

Patients aged 1-7 who have been diagnosed with autism spectrum disorder and global developmental delay according to DSM-5 by 2 child care physicians and/or psychiatrists with associate senior professional titles or above.

Data is confidential during the study.