Manabu Oi: United Graduate School of Child Development, Kanazawa University, Bldg D, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan. oimanabu@ed.kanazawa-u.ac.jp. ORCID
Hiroshi Fujino: Faculty of Education, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo, 184-0015, Japan.
Naotake Tsukidate: Department of Humanities, Yamanshi Eiwa College, 888 Yokonemachi, Kofu, Yamanashi, 400-8555, Japan.
Yoko Kamio: Department of Child and Adolescent Mental Health, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashimachi, Kodaira, Tokyo, 187-8551, Japan.
Yuko Yoshimura: Research Center for Child Mental Development, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan.
Mitsuru Kikuchi: Research Center for Child Mental Development, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan.
Chiaki Hasegawa: Research Center for Child Mental Development, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan.
Keiko Gondou: Department of Child Studies, Faculty of Home Economics, Kyoritsu Women's University, 2-2-1 Hitotsubashi, Chiyoda, Tokyo, 101-8437, Japan.
Tomoko Matsui: Center for Research in International Education, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo, 184-0015, Japan.
The Japanese version of the Children's Communication Checklist-2 (CCC-2) was rated by caregivers in a large national population sample of 22,871 children aged 3-15 years. The General Communication Composite (GCC) of the CCC-2 exhibited a distribution with a single-factor structure. The GCC distribution between autism spectrum disorders (ASD) and language impairment (LI) groups in the general population fit inside a bell curve with significant overlap with the general population, and a continuum was evident between groups. No evidence of a natural cutoff that would differentiate categorically affected from unaffected children was seen. The Social Interaction Deviance Composite (SIDC) supported the notion that ASD and LI are on the opposite endpoints of a SIDC continuum of communication impairment.
