Extended-Release Lithium Treatment for Adolescents with Bipolar Disorder with or Without Comorbid Autism Spectrum Disorder: Protocol of a Longitudinal Prospective Naturalistic Study for the Assessment of Efficacy and Tolerability.

: Lithium is the gold-standard treatment for Bipolar Disorder (BD) in both adults and adolescents, effectively managing mood episodes and reducing suicide risk. While its efficacy in neurotypical youth is well established, its use in adolescents with Autism Spectrum Disorder (ASD) and comorbid BD remains under-researched. Here, we present the protocol for a study aiming to evaluate the efficacy and tolerability of Extended-Release Lithium Salts in treating adolescents with BD and comorbid ASD compared to neurotypical BD patients. : This longitudinal prospective naturalistic comparative study will enroll lithium-naïve adolescents aged 12-18 with BD, with or without comorbid ASD, from the Department of Child and Adolescent Psychiatry and Psychopharmacology. Participants will be followed for six months while receiving Extended-Release Lithium Salts treatment. Primary outcomes will include mood instability, suicidality, emotional dysregulation, and aggression, assessed through a range of clinical rating scales and diagnostic tools at baseline, three months, and six months. Secondary outcomes will focus on the safety and tolerability of Extended-Release Lithium Salts, with measures including side effect ratings, physical exams, and laboratory tests. : We hypothesize that Extended-Release Lithium Salts will demonstrate non-inferiority in treating BD symptoms in adolescents with comorbid ASD compared to those without ASD. : This study is poised to fill a significant gap in the literature by providing critical data on the use of lithium for adolescents with BD and ASD. Findings will inform clinical practice and future research, potentially guiding more personalized treatment approaches for this complex and vulnerable population.