The study examines the structure of psychopathology using data from the Dunedin Multidisciplinary Health and Development Study, a comprehensive longitudinal study of mental disorders. The researchers tested three models to understand the underlying structure of psychiatric disorders: a correlated-factors model, a hierarchical or bifactor model, and a one-factor model. The results suggest that mental disorders can be summarized by three core dimensions: Internalizing (depression and anxiety), Externalizing (antisocial and substance-use disorders), and Thought Disorder (psychotic symptoms). Additionally, the study found evidence for a single General Psychopathology factor, which explains why it is challenging to find specific causes, consequences, biomarkers, and treatments for individual mental disorders. Higher scores on this General Psychopathology factor are associated with more severe life impairment, worse developmental histories, and compromised early-life brain function. The study also explored the correlates of these disorder liabilities, including personality functioning, life impairment, family histories, developmental histories, and brain integrity. The findings highlight the need for transdiagnostic approaches in psychiatric research and suggest that a general factor of psychopathology may exist, similar to the g factor of general intelligence.The study examines the structure of psychopathology using data from the Dunedin Multidisciplinary Health and Development Study, a comprehensive longitudinal study of mental disorders. The researchers tested three models to understand the underlying structure of psychiatric disorders: a correlated-factors model, a hierarchical or bifactor model, and a one-factor model. The results suggest that mental disorders can be summarized by three core dimensions: Internalizing (depression and anxiety), Externalizing (antisocial and substance-use disorders), and Thought Disorder (psychotic symptoms). Additionally, the study found evidence for a single General Psychopathology factor, which explains why it is challenging to find specific causes, consequences, biomarkers, and treatments for individual mental disorders. Higher scores on this General Psychopathology factor are associated with more severe life impairment, worse developmental histories, and compromised early-life brain function. The study also explored the correlates of these disorder liabilities, including personality functioning, life impairment, family histories, developmental histories, and brain integrity. The findings highlight the need for transdiagnostic approaches in psychiatric research and suggest that a general factor of psychopathology may exist, similar to the g factor of general intelligence.