What Causes Abnormality?

Think about the lady in the coffee shop, yelling out nonsense words. Why would anyone do that? What's wrong with her? There are two theories about what causes abnormality: the somatogenic theory and psychogenic theory.
Somatogenic theory states that abnormality is caused by a biological disorder or illness. In the example above, somatogenic theory would say that there's something wrong with her brain. Perhaps she has damage to the left side of her brain, which causes language disorders. Or, maybe she has damage to the bottom part of the front of the brain, which makes people do things that are socially inappropriate. Either way, somatogenic theory explains abnormality in terms of physical causes. As such, a somatogenic approach to abnormality often focuses on using drugs, surgery or other physical therapies to treat psychological disorders.
Compare that to psychogenic theory, which says that abnormality stems from psychological problems. For example, Sigmund Freud might say that the woman in the cafe has an underdeveloped superego, which means that she can't stop her urges like wanting to call out in a public place. Treatment for abnormality based on psychogenic theory includes talk therapy and hypnosis.
Of course, most psychologists don't believe in one theory or the other. Most psychologists believe in one theory more than the other, but will admit that they both play a role in abnormality.