<p>This study explores the influence of food security on the mental health of rural poor smallholder farmers with low levels of income in Nigeria, who remain among the most socially and physically disadvantaged and consequently report suffering a high burden of mental distress. We collected survey data on 780 farmers and evaluated mental health status with two instruments that have been validated: the Kessler Psychological Distress Scale (K-10) and the Center for Epidemiologic Studies Depression Scale. Food security is assessed with a set of binary indicators (e.g., those who had skipped meals or gone without food for a whole day) and a more nuanced Food Insecurity Experience Scale. To find causal effects, we used several estimation methods. Most importantly, we employed an instrumental variable technique with distance to the nearest city as an exogenous predictor of food security and not directly affecting mental health. These control the influence of food security on psychological well-being. Across our results, we found a robust and strongly statistically significant relationship: food security and mental health outcomes are significantly positively correlated. Yet the gains are biased toward farmers with better resource endowments, i.e., farmers with higher educational levels and more secure land control. These results suggest that while improving food access can alleviate mental health burdens, its effectiveness is amplified when combined with broader structural supports. Policy efforts that promote educational access and secure land rights could therefore play a crucial role in reducing mental distress among vulnerable rural populations.</p>