Are Mental Illnesses Biological Diseases? Some Public Policy Implications

In the recently published Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (DSM-IV) (American Psychiatric Association [APA], 1994), APA departed from its historically dichotomized classification of mental illnesses as being of either "organic" or "functional" etiology. In all previous diagnostic manuals, beginning with the DSM-I in 1952, APA had categorized a mental disorder as organic if it was associated with an observable or patently inferable brain tissue impairment or lesion, such as vascular dementia or Alzheimer's disease, and as functional if no such association could be established. The primary causes of functional mental disorders were assumed to be psychological factors, social factors, or both. In one simple and breathtaking sentence contained in DSM-IV, the reader is informed that "The term 'organic disorder' is no longer used in DSM-IV because it incorrectly implies that the other mental disorders in the manual do not have a biological basis" (APA, 1994, p. 10). When one examines the range of human behaviors designated as mental disorders in DSM-IV (some 300 entities, compared to about 100 in DSM-I), it is obvious that there is a wide spectrum in terms of presumed severity - for example, "paranoid type schizophrenia" at one end to "caffeine-induced sleep disorder" at the other. PARTIES TO THE DEBATE Today a major contentious issue among mental health professionals and others is whether the severe mental illnesses that were formerly regarded as functional in origin are in fact caused by biological or physical abnormalities - that is, whether they are organic diseases. Attention in this debate has tended to focus mostly on schizophrenia, manic depression (now known as bipolar disorder), and severe depression (now referred to as major depressive disorder). In addition to these profound clinical entities, the debate has often spread to other, and in a sense less dramatic, psychiatric classifications such as panic attacks, substance dependence, bulimia, obsessive-compulsive disorder, and attention deficit disorder. The chief proponents of a biological-physical etiology for the major mental illnesses tend to be found among biopsychiatrists and behavioral geneticists, advocacy groups whose membership consists for the most part of mothers and fathers of mentally ill people, and pharmaceutical companies that have high-volume sales of psychoactive drugs. The dissenters and the agnostics are a more diffuse group who are less proactive and visible. They include mental health professionals from all disciplines (psychiatry, psychology, and social work) and social scientists whose clinical experiences or research attest to the view that environmental, psychological, and social factors can be significant causative agents of serious mental illnesses. The dissenters also include a number of loosely organized former mental patient groups whose members had often been involuntarily committed and who had been forced to submit to somatic therapies, including drugs and electroconvulsive therapy. The agnostics include a large segment of the medical and scientific communities who adhere to the fundamental precept that there is a distinction among a hypothesis, a theory, and a fact. THE DEBATE To understand the intellectual underpinnings of the debate, it is useful to dispose of a number of semantic and logical confusions or contortions. First, because all human thought and behaviors associated with those thoughts are associated with human brain activity, it should be obvious that any thought-behavior activity, whether normal or disordered, is happening through some biological process. Second, although studies show that close relatives of individuals with schizophrenia or bipolar disorder are more susceptible to these disorders than the average person, studies also show that the close relatives of individuals manifesting almost any of the lesser mental disorders are also more susceptible to these disorders than the average person. …