The article explores the structure of psychiatric disorders, challenging the traditional view of them as distinct and categorical. Using the Dunedin Multidisciplinary Health and Development Study, the authors examined psychopathology across 20 years, from adolescence to midlife, considering dimensionality, persistence, co-occurrence, and sequential comorbidity. Initially, three higher-order factors (Internalizing, Externalizing, and Thought Disorder) explained psychiatric disorders, but a single General Psychopathology dimension (the "p factor") explained them better. The p factor is conceptually similar to the "g factor" of general intelligence, representing a broad dimension of psychopathology that is associated with more life impairment, greater familiality, worse developmental histories, and compromised early-life brain function. The p factor explains the difficulty in finding specific causes, consequences, biomarkers, and treatments for individual mental disorders. Transdiagnostic approaches may improve research. The study found that mental disorders are sequentially comorbid, recurrent, and exist on a continuum. The p factor accounts for the high rates of comorbidity observed in mental disorders, suggesting a more parsimonious structure than current nosologies. The study also found that psychotic disorders can be included in models of psychopathology, and that symptom variation above and below diagnostic cut points implies modeling disorder data at the level of symptom scales. The possibility of one General Psychopathology factor was tested, and the results supported the existence of a general factor that summarizes individuals' propensity to develop any and all forms of common psychopathologies. The study found that the p factor is associated with life impairment, familiality, worse developmental histories, and compromised early-life brain function. The p factor is also associated with personality functioning, life impairment, family histories, and brain integrity. The study concludes that the p factor is a dimension that unites all disorders and has neurological roots. The findings suggest that the structure of common psychiatric disorders in the population is insufficiently described without including disordered thought. The p factor may represent low-to-high psychopathology severity, and higher scores on this dimension are associated with worse outcomes. The study highlights the importance of considering the p factor in understanding the structure of psychopathology and the need for transdiagnostic approaches in research.The article explores the structure of psychiatric disorders, challenging the traditional view of them as distinct and categorical. Using the Dunedin Multidisciplinary Health and Development Study, the authors examined psychopathology across 20 years, from adolescence to midlife, considering dimensionality, persistence, co-occurrence, and sequential comorbidity. Initially, three higher-order factors (Internalizing, Externalizing, and Thought Disorder) explained psychiatric disorders, but a single General Psychopathology dimension (the "p factor") explained them better. The p factor is conceptually similar to the "g factor" of general intelligence, representing a broad dimension of psychopathology that is associated with more life impairment, greater familiality, worse developmental histories, and compromised early-life brain function. The p factor explains the difficulty in finding specific causes, consequences, biomarkers, and treatments for individual mental disorders. Transdiagnostic approaches may improve research. The study found that mental disorders are sequentially comorbid, recurrent, and exist on a continuum. The p factor accounts for the high rates of comorbidity observed in mental disorders, suggesting a more parsimonious structure than current nosologies. The study also found that psychotic disorders can be included in models of psychopathology, and that symptom variation above and below diagnostic cut points implies modeling disorder data at the level of symptom scales. The possibility of one General Psychopathology factor was tested, and the results supported the existence of a general factor that summarizes individuals' propensity to develop any and all forms of common psychopathologies. The study found that the p factor is associated with life impairment, familiality, worse developmental histories, and compromised early-life brain function. The p factor is also associated with personality functioning, life impairment, family histories, and brain integrity. The study concludes that the p factor is a dimension that unites all disorders and has neurological roots. The findings suggest that the structure of common psychiatric disorders in the population is insufficiently described without including disordered thought. The p factor may represent low-to-high psychopathology severity, and higher scores on this dimension are associated with worse outcomes. The study highlights the importance of considering the p factor in understanding the structure of psychopathology and the need for transdiagnostic approaches in research.