Conversely, loneliness has been found to weaken the immune system, to lead to depression and increase our perception of fatigue and pain. This generates inflammation, a condition linked to several serious illnesses, including heart disease, diabetes and cancer. Studies suggest solitary people tend to react with higher levels of stress to situations in their daily life, which may end up causing chronic stress and disrupting their immune system. INNATE STRESS REACTION UCLA researcher, Steven Cole, traces this response back to our evolution. When our ancestors grouped together, their bodies reinforced the immune system as a proactive reaction to the increased risk of infection by bacteria and viruses; but when they were alone and more vulnerable to predators, the body’s response prioritized alertness, increasing heart rate and blood flow in preparation for an attack.