{"doi":"10.1111/pcn.13912","title":"Possible bimodality in the age distribution of pediatric functional neurological disorder","abstract":"Pediatric functional neurological disorder (FND) presents with various symptoms, including limb weakness, gait disturbance, tremor, seizures, and sensory disturbance, while patients' brains show no identifiable organic pathology.1-3 FND can occur as early as 3 or 4 years of age, but is more commonly reported in adolescents (over 10 years of age) who often face greater physical and psychological stressors in family, school, and social life.2, 3 A resting-state fMRI study in pediatric FND showed dysregulation within and across brain networks; an EEG study demonstrated overactivation of networks involved in threat detection; and an inpatient study found a blunted cortisol awakening response, suggesting hypothalamic–pituitary–adrenal (HPA) dysregulation.2 A recent perspective, based on the Ernst Strüngmann Forum on Youth Mental Health, hypothesizes that there are sensitive periods for neuroplasticity—windows when brain connectivity is most malleable—that emerge sequentially with overlap across different neural systems.4 For example, the threat-regulation system (involving cortical-hippocampal-amygdala networks) may be most plastic at earlier ages (3–20 years, peaking around 10–13) than the HPA-axis system (6–23 years, peaking around 13–16). This is followed by other systems such as prefrontal cortex connectivity and social cognition.4 This neurodevelopmental variation could contribute to variability in age at onset. For instance, the age distribution of anxiety disorder exhibits two onset peaks (one at 5.5 years and the other at 15.5 years)—a pattern that may reflect sensitive developmental periods related to threat-regulation and HPA-axis systems.4 However, no formal analysis has tested whether the age distribution of pediatric FND has a single peak or multiple peaks. Therefore, we aimed to identify and analyze secondary datasets that provide patient counts by single-year age category. Notably, most clinical studies of pediatric FND reported age using the mean or median (with range or interquartile range) in their “Table 1,” implicitly suggesting a single peak at 12–14 years (reviews3, 5). We identified three cohorts, among all the 23 pediatric FND cohorts we found, that had suitable publicly available data including patient counts for single-year age categories5-7 (see details in Table S1). First, Grattan-Smith et al. described 52 pediatric FND cases (69% motor, 77% sensory, and 15% seizure) in New South Wales, Australia (1975–1984), with age at admission recorded.6 The diagnosis was made by general pediatricians, pediatric neurologists, or child psychiatrists based on DSM-III; 90% of the patients underwent a formal psychiatric evaluation. Second, Raper et al. reported 124 pediatric FND cases (41% seizure, 18% sensory, and 16% motor) in Newcastle, UK (1997–2017) with age at presentation recorded.7 Twenty-seven of these patients were ≥ 16 years old and were excluded, leaving 97 cases for analysis. The diagnosis was made by pediatric neurologists based on ICD-10. Third, Yong et al. documented 97 pediatric cases (41% motor, 41% sensory, and 20% seizure) in Edinburgh, UK (2018–2020) with age at diagnosis recorded.5 The diagnosis was made by pediatric neurologists or general pediatricians based on DSM-5. Note that differences in diagnostic criteria across the cohorts (e.g., ICD-10 and DSM-III require a preceding psychological stress and a thorough differential diagnosis, whereas DSM-5 does not require a preceding psychological stress but emphasizes an inconsistency between neurological examination findings and symptoms1) might contribute to differing characteristics of the three cohorts. We primarily applied a Gaussian mixture model (GMM), which represents a data distribution as a weighted combination of multiple normal distribution components,8 to the combined data of the three cohorts (n = 246) and to each cohort (Fig. 1). We assumed one or two components (i.e., one and two peaks) and compared the model fits using the Bayesian Info","journal":"Psychiatry and Clinical Neurosciences","year":2025,"id":579107,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9608,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1489339,"name":"Hiroshi Azuma","orcid":"0000-0002-2225-9326","position":1,"is_corresponding":false},{"id":350864,"name":"Akihiro Nishi","orcid":"0000-0003-1629-5985","position":0,"is_corresponding":true}],"reference_count":8,"raw_metadata":null,"created_at":"2026-07-19T02:58:30.282164Z","pmid":"41137726","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}