Cholesterol is a vitally important substance in your body, and lowering it excessively might have harmful side effects. Several research papers have linked low cholesterol levels with suicide, accidents and violence. At this stage no one knows for sure whether the emotional state that produces suicide or violence results in low cholesterol, or whether a cholesterol deficiency predisposes a person to this type of behavior. However, knowing how important cholesterol is to brain health, it is probably the latter. Sixty percent of the dry weight of your brain is fat. Cholesterol is a vital component of the brain’s structure, of cell membranes, serotonin function and nerve transmission. It makes sense then that if cholesterol drops too low, mood might suffer. In recent years, low cholesterol has been shown to impair the function of the serotonin 1A and serotonin 7 receptors, and reduce the ability of the serotonin transporter to transport serotonin in and out of a synapse (nerve space). What is defined as low cholesterol? Most studies have shown that a total cholesterol level below 181 mg/dL (4.7mmol/L) is associated with adverse health outcomes. Excessively high cholesterol can be a problem as well, but needs to be taken in context with overall metabolic health, and other markers such as triglycerides, blood sugar and LDL particle size. Learn more. Source