Vegetable oil may have something to do with neuropsychiatric conditions, including neuroinflammation, anxiety, and depression. Research has found processed foods, especially the origin of the fat content, are associated with many of our neuropsychiatric conditions.
Processed food contains primarily PUFA (polyunsaturated fatty acids) omega-6 vegetable oils. Rancidity in vegetable oils is difficult for the human palate to discern, and therefore shelf stability of processed foods can be prolonged. The standard American diet has a greater than 20:1 ratio of the bad omega-6 oils to the good omega-3. This distorted ratio is associated with many neuropsychiatric dysfunctions, including profound anxiety. Restoring a healthy ratio of 4:1 (even by supplementing omega-3) seems to reduce this profound anxiety.
Buydens-Branchey, L., & Branchey, M. (2007). Long-chain n-3 polyunsaturated fatty acids decrease feelings of anger in substance abusers. Psychiatry research, 157(1-3), 95–104. doi:10.1016/j.psychres.2007.01.004