Electrical status epilepticus in sleep (ESES) is an electrographic pattern associated with cognitive impairment. Our study aimed to prospectively evaluate the psychiatric findings and language skills in patients diagnosed with ESES and to determine the immune modulatory treatment-responsive subgroups. We assessed the patients for psychiatric features and language skills at the baseline and 12 months after. Psychiatric disorders were screened according to DSM-V criteria. We implemented standardized tests including Clinical Global Impressions-Severity Scale (CGI-S), Revised-Children Anxiety and Depression Scale, Children's Sleep Habits Questionnaire-Abbreviated, Aberrant Behavior Checklist (ABC), and Childhood Autism Rating Scale. We used tests adapted/developed for Turkish language including Test of Language Development-Primary-Fourth Edition: Turkish (TOLDP-4:T), Turkish Non-word Repetition Test (TNRT), Turkish Multilingual Sentence Repetition Test (MultiSIT-TR) and Turkish Communication Development Inventory (TCDI). Disability was evaluated by Pediatric Evaluation of Disability Inventory (PEDI). Thirty-nine patients were included. Psychiatric evaluation revealed attention deficit hyperactivity disorder-like symptoms in 25 patients, intellectual disability in 12, and specific learning disability in 8. Patients were treated with corticosteroids or IVIg in addition to anti-seizure medication. The spike wave indexes improved significantly at the end of follow-up period (80 % (65-91) vs. 37 % (24-65), p <
0.001). After 12 months, statistically significant improvement was found in ABC, CGI-S, TOLDP-4:T, TNRT, MultiSIT-TR, TCDI, and PEDI scores (p <
0.05). Patients with improvement in psychiatric symptoms had earlier age. Phonologic working memory performance was significantly preserved and improved compared to other language domains. Immune modulatory treatments may contribute to improvement of psychiatric symptoms and language skills. Preservation of phonologic working memory and grammar performance might be a valuable feature to differentiate ESES-related language impairment.