The power of youth: Long-term differential effects of developmental functioning trajectory on social functioning, quality of life and personal recovery across the schizophrenia spectrum

Background: Compromised developmental functioning is frequently observed in patients with schizophrenia spectrum disorder (SSD) and is associated with poor outcomes, which remains understudied in individuals at varying risk of SSD. This study aimed to investigate the course of developmental functioning and its relationship with long-term outcomes within a population across the vulnerability spectrum of SSD. We hypothesized that developmental functioning negatively correlated with SSD vulnerability, and was positively associated with worse outcomes, regardless of disease status. Methods: We used data of 1119 patients, 1059 siblings, and 586 controls from the Dutch Genetic Risk and Outcome in Psychosis (GROUP) cohort. Group-based trajectory modelling and linear mixed models were employed to investigate the course of developmental functioning (measured by the Premorbid Adjustment Scale) and its associations with the outcomes, including social functioning (SF), personal recovery (PR), and quality of life (QoL). Results: In the combined sample, six developmental trajectories were identified: normal-stable (12.4 %), normal-slow decrease (12.3 %), mild-stable (46.9 %), all dominated by controls and siblings; and mild-rapid decrease (5.1 %), moderate-stable (16.5 %), and severe-slow decrease (6.8 %) more prevalent in patients. Compared to normal-stable, all other trajectories in developmental functioning were correlated with decreased SF; mild-rapid decrease and severe-slow decrease were linked to lower QoL. No association with PR was observed. Conclusion: Impaired developmental functioning variably lowers prolonged SF and QoL but not PR. Potentially influenced by factors encompassing environment, cognition, resilience and disease status, this finding demands screening for developmental deviance among youths and early preventive interventions to achieve normal functioning through a public health salutogenic approach.