Refining criteria for a neurodevelopmental sub-phenotype of bipolar disorders: a FondaMental Advanced Centers of Expertise for Bipolar Disorders study.

Background: Bipolar disorder (BD) is a complex and heterogeneous psychiatric disorder. Neurodevelopmental factors were suggested to contribute to the etiology of BD, yet a specific neurodevelopmental phenotype of the disorder remains unidentified. Our objective was to define and characterize a neurodevelopmental phenotype (NDP) in BD and validate its associations with clinical outcomes, polygenic risk scores (PGS), and treatment responses.

Method: We analyzed the FACE-BD cohort of 4,468 BD patients, a validation cohort of 101 BD patients, and two independent replication datasets of 274 and 89 BD patients. Using factor analyses, we identified a set of criteria for defining NDP. We next developed a scoring system for NDP-load and assessed its association with prognosis, neurological soft signs, polygenic risk scores for neurodevelopmental disorders, and responses to treatment using multiple regressions, adjusted for age and sex with bootstrap replications.

Results: Our study established a NDP in BD consisting of nine clinical features: advanced paternal age, advanced maternal age, childhood maltreatment, attention deficit hyperactivity disorder (ADHD), early onset of BD, early onset of substance use disorders, early onset of anxiety disorders, early onset of eating disorders, specific learning disorders. Patients with higher NDP-load showed a worse prognosis and increased neurological soft signs. Notably, these individuals exhibited a poorer response to lithium treatment. Furthermore, a significant positive correlation was observed between the NDP-load and PGS for ADHD suggesting potential overlapping genetic factors or pathophysiological mechanisms between BD and ADHD.

Conclusions: The proposed NDP constitutes a promising clinical tool for patient stratification in BD.