The study examines the association between obesity and psychiatric disorders in a nationally representative sample of US adults. The National Comorbidity Survey Replication (NCS-R) data were analyzed to assess the relationship between obesity (Body Mass Index, BMI ≥ 30) and mood, anxiety, and substance use disorders. Key findings include: - **Mood and Anxiety Disorders**: Obesity was significantly associated with increased odds of major depression (OR=1.21, 95% CI 1.09 to 1.35), bipolar disorder (OR=1.47, 95% CI 1.12 to 1.93), and panic disorder or agoraphobia (OR=1.27, 95% CI 1.01 to 1.60). The association was strongest in non-Hispanic whites and college graduates. - **Substance Use Disorders**: Obesity was associated with a significantly lower lifetime risk of substance use disorder (OR=0.78, 95% CI 0.65 to 0.93). - **Demographic Variations**: The association between obesity and mood disorders varied by sociodemographic factors, with stronger associations in younger respondents, non-Hispanic Whites, and those with higher educational attainment. - **Mechanisms**: The study suggests that social or cultural factors may moderate the relationship between obesity and mood disorders, possibly through stigma, health behaviors, or common underlying causes. The findings highlight the importance of addressing the bidirectional relationship between obesity and mental health, emphasizing the need for further research to understand the underlying mechanisms and to develop targeted interventions.The study examines the association between obesity and psychiatric disorders in a nationally representative sample of US adults. The National Comorbidity Survey Replication (NCS-R) data were analyzed to assess the relationship between obesity (Body Mass Index, BMI ≥ 30) and mood, anxiety, and substance use disorders. Key findings include: - **Mood and Anxiety Disorders**: Obesity was significantly associated with increased odds of major depression (OR=1.21, 95% CI 1.09 to 1.35), bipolar disorder (OR=1.47, 95% CI 1.12 to 1.93), and panic disorder or agoraphobia (OR=1.27, 95% CI 1.01 to 1.60). The association was strongest in non-Hispanic whites and college graduates. - **Substance Use Disorders**: Obesity was associated with a significantly lower lifetime risk of substance use disorder (OR=0.78, 95% CI 0.65 to 0.93). - **Demographic Variations**: The association between obesity and mood disorders varied by sociodemographic factors, with stronger associations in younger respondents, non-Hispanic Whites, and those with higher educational attainment. - **Mechanisms**: The study suggests that social or cultural factors may moderate the relationship between obesity and mood disorders, possibly through stigma, health behaviors, or common underlying causes. The findings highlight the importance of addressing the bidirectional relationship between obesity and mental health, emphasizing the need for further research to understand the underlying mechanisms and to develop targeted interventions.