The concept of comorbidity in psychopathology has long been a challenge for researchers. Recent studies suggest that explicit quantitative models can help explain and classify comorbidity by identifying latent liability factors that influence multiple disorders. A meta-analysis of a liability spectrum model shows that mental disorders are manifestations of these latent factors, which explain comorbidity through their impact on multiple conditions. This model addresses nosological, structural, etiological, and psychological aspects of comorbidity. The term "comorbidity" originated in medical epidemiology and refers to the presence of additional conditions in a patient with a primary disease. It has gained traction in psychiatric and psychological literature since the late 1980s. However, the term is broad and can refer to both co-occurrence and correlation between disorders. This ambiguity has led to debates about the appropriate terminology and conceptualization of comorbidity. Several models have been proposed to explain comorbidity, including associated liabilities models, multiformity models, causation models, and independence models. These models suggest that comorbidity can result from shared genetic or environmental factors, direct causation, or independent conditions. Multivariate models, which consider multiple disorders simultaneously, provide a more comprehensive understanding of comorbidity by incorporating more complex relationships. Studies have shown that comorbidity is more common than chance would suggest, indicating that mental disorders are significantly correlated. This has led to the development of liability spectrum models, which suggest that mental disorders are manifestations of underlying liability factors. These models have implications for the classification of mental disorders, suggesting that they may be better understood as continuous rather than discrete categories. Behavior genetic studies have also contributed to the understanding of comorbidity, showing that shared genetic factors can explain the correlation between disorders. These findings support the liability spectrum model and suggest that mental disorders may be better understood as continuous constructs rather than distinct categories. Overall, the concept of comorbidity is complex and requires a nuanced understanding of the relationships between disorders, which can be achieved through model-based approaches.The concept of comorbidity in psychopathology has long been a challenge for researchers. Recent studies suggest that explicit quantitative models can help explain and classify comorbidity by identifying latent liability factors that influence multiple disorders. A meta-analysis of a liability spectrum model shows that mental disorders are manifestations of these latent factors, which explain comorbidity through their impact on multiple conditions. This model addresses nosological, structural, etiological, and psychological aspects of comorbidity. The term "comorbidity" originated in medical epidemiology and refers to the presence of additional conditions in a patient with a primary disease. It has gained traction in psychiatric and psychological literature since the late 1980s. However, the term is broad and can refer to both co-occurrence and correlation between disorders. This ambiguity has led to debates about the appropriate terminology and conceptualization of comorbidity. Several models have been proposed to explain comorbidity, including associated liabilities models, multiformity models, causation models, and independence models. These models suggest that comorbidity can result from shared genetic or environmental factors, direct causation, or independent conditions. Multivariate models, which consider multiple disorders simultaneously, provide a more comprehensive understanding of comorbidity by incorporating more complex relationships. Studies have shown that comorbidity is more common than chance would suggest, indicating that mental disorders are significantly correlated. This has led to the development of liability spectrum models, which suggest that mental disorders are manifestations of underlying liability factors. These models have implications for the classification of mental disorders, suggesting that they may be better understood as continuous rather than discrete categories. Behavior genetic studies have also contributed to the understanding of comorbidity, showing that shared genetic factors can explain the correlation between disorders. These findings support the liability spectrum model and suggest that mental disorders may be better understood as continuous constructs rather than distinct categories. Overall, the concept of comorbidity is complex and requires a nuanced understanding of the relationships between disorders, which can be achieved through model-based approaches.