In a rapidly changing society with an increased incidence of stress, people are more likely to get anxious and depressed at the slightest stimulation.
If a research conducted on rhesus monkeys holds good for humans as well, those who tend to be anxious easily are all the more likely to have kids who will grow anxious quickly.
This logically points to the risk of being depressed and anxious being hereditary. It is something present in the genes. It is passed over generations thanks to genes.
Since all three areas of the brain are involved in making decisions, all parts of the brain are responsible for one being anxious and depressed. The involvement of all different areas of the brain in taking decisions is a pointer towards all parts of the brain not working well.
Any form of hyperactivity involved in making decisions is directly involved in the innate tendency to develop anxiety. This is found to be true right from the early years of childhood.
If a study conducted on monkeys is to be considered valid, a study involving 600 monkeys, those with a family-history of inclination towards anxiety showed more inclination to be anxious. There was a variation of only 35 percent from the norm.
The tendency to get anxious can be said to be survival tendency because those who get anxious are more likely to recognize a dangerous situation when they come across one. Someone who doesn't hold the tendency is not likely to become as wary of the dangerous situation.
It is only when the stimulation reaches a limit, and even crosses it, it can become a problem. This is the situation when one gets to be anxious and depressed, and needs special attention.