CBD has been postulated as working in conjunction with the CB1 receptor. Receptors, in general, are proteins that receive chemical signals from outside of cells. When these chemical signals bind to receptors, they initiate a response. Cannabinoids bind to endocannabinoid receptors, and once this interaction has begun, signal transduction pathways turn on, and thus, the physiological effects cannabinoids have on our bodies begins. Scientists think that the CB1 receptor changes serotonin signals. Low serotonin levels have been linked to depression, and they can even cause anxiety in some individuals.