Anxiety disorders are among the most common mental illnesses. Current treatments worldwide are not standardized nor effective as we would wish for, suggesting deeper understanding of the causes of anxiety. To understand anxiety disorders, it is necessary to understand the normal anxiety response. Very basic approach in understanding anxiety is to determine its causes and normal responses.

Evolutionary theory predicts that the threshold for mounting an anxiety response should depend on the probability of dangerous events occurring in the current environment, and the vulnerability of the person to those events as critical criteria. The evolutionary criteria for when a mechanism is functioning adaptively are different from the criteria for identifying when a psychiatric disorder is present.

Treatments for anxiety and depression at present, have limited efficacy. For example, for anxiety – depressive disorders, usage of antidepressants treat successfully every 6th patient. It means 6 patients need to be treated with the drugs to produce 1 clinically significant symptomatic improvement. Generally speaking only about 45% of anxiety patients show a clinically significant response to psychological therapy.

From prehistoric time until modern times evolution by natural selection is the source of all complex physiological organization in nature. It's debatable for some what is evolution by its manifestations in human societies. However, more questions arises where is the boundary between evolved functions and dysfunctions. Evidences suggests that long-term survival is lower in people with a low level of anxiety proneness, than those in the middle of the distribution.

Animals display set of responses in their normal behavior and consists of increased heart rate, stress hormone secretion, restlessness, fear of potentially dangerous environments, and decreased feeding and exploratory behavior. It also involves an increased tendency to interpret ambiguous stimuli as threatening.

Modern times are nothing like the times in which our ancestors evolved. Prehistoric men were living in the environment of evolutionary adaptation. Primitive men were hunter-gatherers living in bands. Evolutionary Psychology tend to believe that non natural environment we live today opposes natural selection and organization of human societies, and that is one possible cause of anxiety and depression.

Nowadays we live in global village. News spread by all means. Most of news we receive are so called “Bad news” and is debatable source of anxiety in many. We have access to the bad news of six billion people, more than could be generated by a hunter-gatherer band at a primitive tribe. Such a symptomatic stress during primitive times were discussed and so shared with other group members, whereas modern man tends to watch it, or listen to it on his own mostly without comment it loudly.

Anxiety and depressive disorders play important roles in managing the organization of a social hierarchy. Social anxiety disorder is mostly obsessed with avoiding harm from human interactions, and is interested in social balance and equality. However, there's a difference between anxious mood and anxious emotion. Anxious emotion is directed and sensitive to by object changes. In contrary, anxious mood is self-focused, and is unchallenged by changes in the environment. Emotions and moods are mediated by different levels of the brain. Great example of this is Mac-Lean's model of the triune brain representing depressed emotion and anxious emotion. Depressed emotion and anxious emotion are mediated by the paleomammalian forebrain, whereas depressed mood and anxious mood are mediated by reptilian forebrain.

Ancient philosophers used the metaphor of the cart, horse, and driver. The driver represented reason, or the rational mind, with only limited control over the horse, which represented the emotional mind, with limited control of the cart, representing the instinctive mind. In humans, our neomammalian brain recognizes as rational thought and decision-making not only on modern problems such as technology and litigation, but, also on the older problems related to reptilian and paleomammalian brains such as avoidance of danger, courtship, and competition.

For over three hundred million years, competition between our ancestors took the form of agonistic ritual behavior in the sense that it obeys certain rules. Basic rule is that each individual has a limit, in the punishment he is able to receive before switching from escalation to de-escalation. Another rule is that, when one contestant submits, the winner exercises mercy and docs not take advantage of any submissive posture adopted by the loser.

Various competitions have become more complex over the course of evolution. Conflicts within group members in primitive societies could take long time to be resolved. Instead of fleeing during the course, the loser could remain to live in the group within the contest winner. Such new approach gave rise to submissive behavior, and as result this produced the capacity of individuals to live in a subordinate social role. Anxiety and fear of the dominant individuals triggered the social hierarchy in order to maintain stability as preventing possible rebellion. At some point during evolution, this stabilizing anxiety gave rise to a certain respect of the higher-ranking individuals and thus, social rank was determined by the choice of the group.

The capacity for escalation and de-escalation survived the switch to prestige competition different forms. Pursuit of the goals replaces the decision to attack, so escalation got adoption of new goals, and de-escalation consists of giving up goals. Socially speaking, escalation took the form of self-assertion, such as standing up to speak and promoting one's own goals, whereas de-escalation takes the form of self-effacement by allowing other people's goals to take precedence in the group. At the emotional level, escalation takes the form of enthusiasm, and self-confidence. De-escalation reflects the fact that punishment, comes from the group rather than from a dominant individual, so there how social anxiety is formed by guilt, and shame.

Evolutionary aspects believes that roots of depression and anxiety goes back to our ancestors complete absence of attachment to family life, or even pair-bonding. In such relations with the opposite sex they were restricted to courtship and with the same sex to ritual agonistic behavior. When attachment evolved, it had a profound effect. Depression and anxiety after experiencing loss represent a precursor mood change to adjust the individual to lower status.

Evolutionary aspect believes that injustices and competitiveness of the developed world are seen as recent cultural pathologies. In contrary to our modern lifestyles our ancestors had the capacity to live in both equality and inequality, accepting it willingly and producing as result depression and anxiety in conditions when applied inequality.

In general, rational brain has little control over the emotional brain but only mediation applies as effect in positive and negative way. Common to poker players is adaptation to perform “poker face,” in order that his opponents can't see his excitement when he picks up and looks at a great deal in his hand. Chinese jade retailers brushed their skills in fully understanding customers who will hide pleasure in observing a particularly desirable piece. Therefore retailers look at the customer's pupils for dilation of excitement. This is a positive affect over which the rational brain has no control.

In some social situations, hideouts of negative affect is not required, nor expected. People are motivated to hide the manifestations of depression and anxiety from others. In social circumstances when we are up to prestige competition, individuals try to present themselves as competent and in charge of the social situation. In most cultures, people like to associate with successful others, and avoid those who show signs of failure. As a matter of fact, it has been found that depressed and anxious individuals are found to be socially aversive and are avoided by others.

In real life situations related to competition, people are motivated to encourage their allies to perform as well as possible, and particularly parents are motivated to push their children to optimal performance, trying to launch their children into social orbits higher than their own social status. Social anxiety is mostly a solitary output, endured by an individual harmed by a dominant, or by a whipping boy and punished by the group. In contrary, nonsocial anxiety has sources of harm often shared with other group members and eventually becomes a social experience, modulated by social customs. In some cases, the group comes together to reduce anxiety.

It seems that anxiety is easier than other disorders to grasp it because of its function in avoidance of harmful situations. Parents try to train their children to be anxious about traffic, strange men, drugs, and other dangers, which did not appear in the optimal environment, and so have no built-in avoidance mechanism. In a way anxiety is much more difficult to analyze than depression. Anxiety is a complex mix of cognitive, affective, behavioral, and somatic components, with complex relations to other aspects of motivation. The function of depression is entirely social, whereas anxiety has to keep the individual safe from countless nonsocial dangers in addition to threats from conspecifics. Anxiety motivates the individual to escape danger and work hard to avoid social disgrace. On the other hand, too much anxiety impairs performance, and may actually impede attempts to escape or avoid danger.

It is clear that anxiety has adaptive and protective function. For instance, for person who cross Himalayan every now and then would not last for long. Anxious avoidance of snakes and spiders obviously saved many life's so far. Fact is that there's not yet established anxiety about electric cars and space traveling, indicates that evolution has had no time to build up anxiety about these dangers.

In the end I would like to mention Aristotle. He made interesting observation. If someone hits you, you will definitely experience pain. If higher ranking individual is the one who caused pain, you will feel sad. If pain is caused by lower ranking individual, you will feel angry. Instinctively your reactions will be determine by sub-rational brain. With our rational brain we can choose to fight or submit, and we can choose to feel angry or to feel sad and anxious, which in return will determine our life strategy and social status.