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In the following paper, an assessment shall be made of how biology/neurobiology has impacted the study and diagnosis of mental illness. Two general conclusions will be drawn from this presentation. The first of these conclusions is that with time, money, and increased research, there will be an ever-expanding ability to discern biological and material identifiers of mental illness. The second conclusion that shall be drawn is that there will be a continued trend towards "blurring" the border between "normal" and "abnormal" behavior as mental illness is increasingly better understood. Each of these conclusions raises new issues that shall be addressed in the body of this paper.
It was not before the 1950s that mental illness was considered worthy of major study in medicine. Even today, the mode of recognizing brain and mind linkages most often occurs across several disciplines. Thus, the challenge of developing a scientific psychopathology through integration of these cross-disciplines still remains an arduous task. The study of the mind has primarily fallen under the jurisdiction of the cognitive psychologists, while the study of the brain has generally fallen into the domain of neurologists (further subdivided within this discipline). Given this current state of affairs, how does one honestly come to understand that which dictates the manifestation of mental illness?
Currently, there are no known biological makers for any mental illness other than dementias such as Alzheimer's disease. (1) In the absence of pathological markers, the current definitions of mental illnesses are syndromal and based on a pattern of behavior and familial aggregation. (2) Locating the neural mechanisms involved in producing mental illness is an iterative process, requiring a methodological approach, much like other diseases. Still, the task of defining what constitutes "normal" and what constitutes "mentally ill" is not necessarily an objective one. Thus, such research can be challenging and potentially mired down in ethical issues over neurological ones.
Lingering myths, concerning such illnesses as schizophrenia, have gradually yielded to new treatments and understanding of what constitutes mental illness. Still, a myopic view of such an illness has often been accepted as the norm. For decades, schizophrenia was blamed on bad parenting or even on the individual him or herself. (3) Recently, however, the disease has been found to have genetic links, where subtle deformations in the brain can occur as early as in the womb. In two reports published in the Lancet (June, 1997), researchers were able to identify that positive symptoms related either to the over-perfusion or the under-perfusion of blood in the prefrontal cortex region of the brain. (4) Further studies by researchers at the National Academy of Sciences have linked impaired functioning of the cerebellum to the onset of schizophrenia. (5) As this research progresses, a better understanding of neural mechanisms underlying such mental illnesses as schizophrenia has been obtained through an analysis of the underlying cognitive function that is injured and the underlying neural circuitry of that cognitive function. (5 and 6) Similar data has been gathered on individuals experiencing violent episodic outbursts. (7 and 8)
The two pieces of research presented above on schizophrenia exemplify the increasing trend and interest towards the advanced and integrated study of mental illness. Thus, as research continues, it will become increasingly likely that further biological markers will be developed to better identify and adequately diagnose various forms of mental illness. This raises the further issue of what factors trigger human behavior. Is the way one behaves simply biologically based, or do environmental causes play a role in impacting the "output" of behavior? If one assumes that the nervous system is, on the whole and at the level of the neuron itself, a collection of input/output devices, then one is capable of monitoring inputs and outputs entering the brain. Likewise , it can be stated that the specific inputs and outputs are not only dependent upon environmental stimuli, but also upon the very make up of the neuron itself. (9) Research on the topic so far has supported both an environmental and physiological role in the outcome of an individual's mental state.
Given this assertion, one must briefly address the notion of "free will". Can an individual ever act "freely" and if so, how much control does one's own "biology" have over the environment in which one exists? (10) Given the intrinsic variability in input/output boxes at all levels of organization, the state of the nervous system at a given time depends not only on its inputs at that time but also on the history of its past inputs as well. (9) Thus, the notion of what constitutes "free will" is not limited to a given individual's outputs, but rather through a constant exchange of information between the environment and the biological makeup of the individual.
As the notion of free will and the relation of brain and mind are further explored, it remains essential to continue to actively define what constitutes "normal" vs. "abnormal" behavior. This ongoing reassessment of "normalcy" is of pressing importance for both economic as well as humanitarian reasons. As noted in the New York Times in 1996, approximately one-fifth of American adults experience some form of disorder affecting emotions, thoughts, personality or behavior during the course of a year. Of these, approximately 3%, or 5 million adults, are considered severely mentally ill. Expenditures for these individuals have run over $150 billion in annual costs. (5)
Thus, a definition of a "boundary" between "normal" and "abnormal" cognitive processes is of primary importance in identifying neural substrates of mental illness. Still, it continues to be an arduous task. Many of the symptoms defining mental illness run in a continuum with normal behavior. At what point does extreme depression turn into a psychopathological disease? When does a rambunctious child have a severe enough condition to be labeled as attention deficit disorder? Thresholds of severity or duration are generally the measure used to resolve such a problem. (11) Still, these remain boundaries of convenience, not ones with inherent biological meaning attached.
Thus, as research progresses, one can assert that there will be a continued blurring of the border between "normal" and "abnormal" behavior. This ongoing process of defining mental illness through what appears to be somewhat subjective boundaries may seem imprecise. Certainly, the biomedical paradigm that prevails throughout the Western world of medicine generally considers disease to be distinct from normalcy. One either has cancer or one does not. Still recent findings concerning the genetic risk factors associated with developing a disease (through measurements premorbidly of the BRCA1 and ApoE lipoproteins) raises similar questions about the discontinuity requirement involved in defining a disease process. Thus, current models of mental illness may, in fact, share a closer etiology with cancer than was previously imagined. (1)
The creation of a scientific and testable model of mental illness may be generated from a variety of disciplines, such as neurobiology, neuropsychology, cognitive psychology, or psychiatry. For neurobiologists, the underlying linkage between brain and behavior has been the assumption that behavior and the nervous system are one in the same. Likewise, it has been presumed that an understanding of the nervous system structure and function would confer an advantage in understanding human behavior. (9) With the neurological model of an "input/output" system of information exchange, neurologists have been able to consider mental illness at both the level of systems as well as a more acute biological level of information exchange (where axons and dendrites synapse as input and output affect one another). Cognitive psychologists tend to consider behavior manifestations at a more macro level n potentially examining more psycho-social issues defining mental illness and what is considered "normal" and "abnormal". Whatever the point of origin, these models converge on one common pathway to lead to a set of shared characteristics.
It is only through the use of cognitive modeling that mental illness can be categorized and properly examined in a modern scientific era. These models must essentially share three characteristics to be useful: first, they must provide a general definition of the disease that is consistent with the biomedical model that is currently implemented in medical settings; second, they must offer a theory that is testable in human beings; and third, they must provide a theory that is able to be modeled and tested in animals. (1) With these three criteria in place, there is a greater possibility for advanced screening as well as improved biomedical understanding of the link between mind and brain, shattering conceptual barriers of what constitutes mental illness.
(1) Andreasen, Nancy C. "Linking Mind and Brain in the study of Mental Illnesses: A Project for a scientific Psychopathology," Science. 14 March 1997. Vol 275, No. 5306 p.1586-1592.
(2) Robins, E. and Guze, S.B. American Journal of Psychiatry. 126, 983 (1970).
(3) "Quieting the voices"
(4) "Researchers zooming in on the brain in schizophrenia patients"
(5) "Erasing the line between Mental and Physical Ills"
(6) "Mood disorders: Pharmacological prevention of recurrences"
(7) "Organic reason for behavior isn't likely" The Inquirer, February 8, 1996
(8) "Research on Violence and Traumatic Stress"
(9) "Variability in Brain Function and Behavior"
(10) "Free will?"
(11) Feighner, J.P. et al. Archives of General Psychiatry. 26, 57, 1972.
A) "That Fine Madness" Discover Magazine, October, 1996
B) "Alcohol, Violence and Aggression"
C) "Rage Disorder"
D) "Epileptic Violence and Criminal Behavior"