11/30/2012 08:20 pm ET Updated Jan 30, 2013

The Origin of Angst: How Ancient Herd Instincts Cause Modern Anxiety and Depression

Imagine for a moment that you are evolution. How would you go about designing biological instincts for social behavior in a herd of animals? It's not only about the survival of the fittest individual; it is also about the survival of the fittest herd. Because animals don't think well enough to make up rules of proper behavior for themselves, they needed help from some biological herd instincts in order to stay safely together, keep infighting at a minimum, build and maintain social homes (clean, save, behave and keep count), maintain herd harmony and know enough to leave the herd when their own diminished contributions make them a drain on limited resources. If you come up with these five instincts for the herd, it will survive and prosper and, most importantly for evolution, pass on their social herd instincts to future generations in their DNA. And then you would have a chance to tinker more with their evolution, and to further improve their prospects. Real evolution has it easier than us: It relies on chance variations that are useful for increasing either individual or group survival. We humans would have to think things through ahead of time to guess what would work better. Mother Nature tinkers better than we do.

Still, there are simple computer simulations that do go a short way toward designing social behaviors. "Boids," for example, creates a flying flock of birds onscreen. It includes four software-coded "instincts": avoid dangerous separation from the flock, keep a proper location in the social space, maintain the essentials of a flying social nest and avoid flying annoyingly close to each other. "Boids" does not include the need to take one for the team when no longer contributing much to the flock. Real evolution has taken these instincts in different and more detailed directions among the animals. No doubt they vary across both species and individuals. Because we humans are a modern version of our own ancient herds, we still have these very same five sociobiological instincts for herd survival -- and one more. A flying flock of birds would have the awareness to scurry at the sight of predators, but we humans are also blessed, and a bit cursed, with more consciousness and reason than any of our animal cousins.

The addition of our ability to think, reason and choose has let use develop our intellectual and social lives, technology, culture and civilization. A large part of how we got where we are is that we are ready, willing and able to defy our innate herd instincts. In particular, doing for ourselves is sometimes more advantageous for our societies than merely doing what is socially best for the herd as a whole. We can think for ourselves, and so far this sounds good. The problem, though, is that those herd instincts are still there underneath. When they sense that we are not doing what they want, they complain and try to coax us back to that ancient herd. The complaints of those five instincts are voiced to us in the corresponding symptoms of panic anxiety, social anxiety, obsessive-compulsive disorder, atypical depression and melancholic depression. These five specific anxiety and depression subtypes painfully try to push us away from our rational choices. Not only can those syndromes be dreadful for us, but they interfere with our attempts to make thought-out choices for ourselves and our societies. Even in the modern world, our instincts tell us to be mindful of the long-ago needs of our primeval herd.

The notion of evolutionary psychiatry is not new: Freud and many others pondered the concept. This novel sociobiological approach makes sense of what we already know about human angst, psychiatric diagnosis and treatment, animal behavior and much more. Besides all the support from scientific research, there is cultural acknowledgement of these ideas in cartoons, jokes, song lyrics and ancient literature. And we humans have evolved even further, of course. For example, we have repurposed some of these painful instincts to new uses. Panic can lead to desperate creativity, and milder OCD to technical perfectionism. Some of us even challenge the pain head-on. Just as firemen head toward a fire, some of our best entertainers are drawn by a need to quell the shyness of their social anxiety. Some workaholics use their unceasing labor to fight off the lethargy, sadness and sensitivity to social rejection of atypical depression. Because these repurposings can help the human herd, we may have evolved so that some of us have stronger versions of these instincts and syndromes than our animal cousins.

This brings us to another question. If you really were evolution, what would you do with the human race today to further enhance the survival, advancement and protection of our collective DNA, our individual lives and our societies and civilization? Your mission, should you decide to accept it, is to imagine an improved future version of ourselves.

Jeffrey P. Kahn, M.D., is author of Angst: Origins of Anxiety and Depression (Oxford University Press) and Clinical Associate Professor of Psychiatry at New York Presbyterian Hospital/Weill Cornell Medical Center, in New York City and Westchester County.