The cause or etiology of mental disorders is still unknown. Most psychologists recognize that abnormal behavior is due to psychological, biological, and social factors.

For most of the twentieth century, psychologists proscribed to one of four main theories that defined the causes of abnormal behavior.

One such theory or paradigm is the biological paradigm. Psychologists that prescribe to the biological paradigm are not concerned with the thought of there patients. They feel that abnormal behavior results solely from the biological makeup of the patient. They were able to able to hang their hat on general paresis. Only some cognitive disorders are solely caused by biology. Biological adherents often over stress the medical model.

Another school of thought is the psychodynamic approach. Its inspiration lies in the writings of Sigmund Freud.Psychodynamic theory attributes abnormal behavior to unconscious mental conflicts that have their roots in early childhood. Freud’s psychoanalytic theory support the psychodynamic approach. Specifically, the id, ego, and superego are key to understanding unconscious conflicts. Defense mechanisms help explain abnormal behavior. Psychodynamic theorists sometimes focus solely on early childhood issues and the unconscious.

The next big player in the twentieth century is the cognitive behavioral theory. The big idea behind this theory is that all behavior, normal and abnormal, is simply learned through classical and operant conditioning. Some psychologists were strict behaviorists who believed that the only appropriate subject for psychology to study was observational behavior. The cognitive behavioral paradigm is prone to disregarding social and biological context of human behavior.

The final significant theory is the humanistic theory. Humanists felt that psychology was far too negative focusing on everyone’s problems rather than looking at the better aspects. They sought to be optimists in a sea of pessimists. Free will played a key role in their theory. They believed that individuals are in complete control of their behavior are responsible for their actions. On the flip side, determinists believe that there are potentially knowable factors that cause a person’s behavior. Humanists are not always the most scientific.

Systems theory was born from the mind of Ludwig von Bertalanffy. He realized that the world isn’t solely black and white. Science is no different. Systems theory is an integrative approach to science and is synonymous with the biopsychosocial model.  Holism is one important aspect of systems theory. It’s the belief that the whole is greater than the sum of its parts. Another key aspect of systems theory is reductionism. This is the process of understanding a problem by reducing it to the smallest possible unit. Systems theory keeps an open mind in terms of causality.Equifinality is the viewpoint that there are various routes to the same destination. You can take different streets and still reach that restaurant so to say. Multifinality is the idea that the same event can lead to different outcomes. In other words, just because you see your friend driving on the same street as you doesn’t necessarily mean you are going to the same place. Reciprocal causality is the idea that causality is a two way process. There aren’t any one way streets in systems theory world. The Diathesis-Stress Model is the idea that certain people are more likely than others to develop a disorder. Just because this is the case, however, does not necessarily mean the disorder will affect them. Certain environmental factors must be present to flip the disorder switch to the “on” position. A big part of understanding developmental psychopathology is an emphasis on developmental norms. You need a baseline to compare behavior against.

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