CELF4 is required for proper CNS development and function. CELF4 deficient mice shows seizures, hyperactivity and hyperphagia-related obesity resembling to neurobehavioral phenotype described in human CELF4 deficiency. CELF4 haploinsufficiency is responsible for the phenotype associated with del (18q) syndrome that is characterized by neurodevelopmental disorder including seizures, intellectual disability, autism spectrum disorder, autism features and/or behavioral disturbances. In most patients 18q12.2 deletion was detected by banding techniques/aCGH/FISH analyses and had variably d deletions encompassing this region (range 18q11-18q21.2). However, a minority of patients had a molecular definition. Haploinsufficiency of CELF4 has been mostly related to 18q12.2 deletion as well as to chromosomal translocations. Most patients had de novo deletions, some patients inherited CELF4 haploinsufficiency from an affected or healthy parent. CELF4 represents one the most significant gene associated with depression in genome-wide association study of depressed patients.