https://medium.com/scientific-american/brains-dumped-dna-may-lead-to-stress-depression-14b5de787228 Reproducing here as this requires a sign in to view. New research suggests genetic material from the mitochondria can trigger an immune response throughout the body Humans and other mammals react to stressful situations through a series of well-orchestrated evolutionary adaptations. When faced with a predator looking for its next meal, or with worry of losing a job, our bodies release a cascade of stress hormones. Our heart rate spikes, breath quickens, muscles tense up and beads of sweat appear. This so-called “fight-or-flight” response served our ancestors well, but its continual activation in our modern-day lives comes with a cost. Scientists are starting to realize stress often exacerbates several diseases, including depression, diabetes, cardiovascular disease, HIV/AIDS and asthma. One theory is hoping to explain the link between stress and such widespread havoc by laying the blame on an unexpected source — the microscopic powerhouses inside each cell.