Psychology Today | 07.11.2026 20:48
Everyone knows, or will likely know one day, what it feels like to be depressed. This is why depression is often referred to as "the common cold of mental illness." This reference reveals some fundamental insights into why we also become depressed when we are suffering from the flu or a bacterial infection. Bacteria induce our bodies to release an ancient form of chemical warfare called cytokines. These cytokines are part of our immune system's defensive arsenal, protecting us from invading bacteria or viruses. When we get sick, we engage in sickness behaviors: we remove ourselves from company and become less active while our bodies try to heal. When your dog is sick, it might hide under the bed and sleep for days, not even eating.
