Loneliness can cause inflammation in your brain. People who feel

socially isolated had higher levels of inflammation markers. They

also showed increased activity of the body’s fight or flight

response. Fight or flight inactivated when a person is under a

stressful situation. It can cause some people to become more

paranoid toward threats. People who are lonely also have poor

decision-making skills and show a decrease in learning and

memory.

People who are socially disconnected show signs of extra aggression with prolonged sessions of loneliness, humans can experience a change in their behavior and the way they interact with the world. This is due to the rewriting of the neural synapses. A study found that mice who spend two weeks in isolation show higher levels of brain chemicals related to stress behaviors. This made them more fearful and prone to erratic reactions. Another study shows that solitary isolation shrinks nerve cells in mice.

Researchers performed a study in mice by isolating them from their community. After a month of isolation, they had smaller nerve cells in certain parts of the brain. The overall size of the neurons shrunk by about 20% after a month of isolation. That shrinkage remained steady over 3 months as the mice remained in isolation. People who are lonely are also more susceptible to illness. 

Lonely a person’s immune system responds differently to fighting viruses making them more likely to develop an illness. Loneliness and physical social isolation can lead to a 30% increased risk of premature death. Research shows that heart patients with chronic loneliness are 3 times more susceptible to the risk of sying than their more social peers. Loneliness is different than physical isolation. Loneliness is actually a state of mind. One study suggests that loneliness may actually be contagious in a ten-year study, the researcher examined how loneliness spreads in social networks. The results showed that people close to someone experiencing loneliness were 52% more likely to become lonely as well.

Isolation or being alone at times isn't always the worst thing. Being alone for a bit of time benefits our default mode network. In default mode network different parts of the brain intercommunicate while are at rest and create a sense of cell-identity. Being alone allows us to contemplate and focus on our lives