Moving Beyond Dualism to Advance Geriatric Neuropsychiatry.

The expansion of life expectancy over the past century coupled with the aging of the baby boom generation has created a shift in demographics. The United States and many countries around the world are experiencing tremendous expansion of their older adult populations, with the fastest growth among the oldest old, typically defined as those over 85 years. 1 As a consequence, the incidence and prevalence of chronic medical diseases as well as age-related neuropsychiatric conditions will increase markedly. Thus, it is imperative to understand the connections between these conditions to find better treatments and to improve care of symptoms of both the brain and the body. Too often, our healthcare system and education has separated diseases of the body and brain and even within brain clinical science have notably divided the fields of neurology and psychiatry. This traditional dualism is outdated and does not serve the best interest of our patients or clinical neuroscience discovery. In this edition of the American Journal of Geriatric Psychiatry, several important contributions underscore this issue. In particular, they remind us that psychiatric symptoms are not uniform and are not necessarily indicative of specific pathophysiology. Rather, they may be more accurately viewed as representing network disruptions that may result from a variety of disease mechanisms. In a detailed clinical study of visual hallucinations, Urwyler et al. 2 found a very high proportion of visual hallucinations among older adults with eye disease. Interestingly, differences in the phenomenology of visual hallucinations stemmed from eye disease as compared with those from Parkinson disease or Lewy body dementia. Those hallucinations associated with eye disease tended to be simple, whereas those with Lewy body dementia were often complex in nature. This finding supports the hypothesis that simple hallucinations are related to pathology within the primary retinocortical visual pathway and complex hallucinations derive from higher cortical dysfunction such as that seen with Lewy body dementia. The study also highlights the need to understand normal neuroanatomic pathways and networks and how disruptions of these may lead to common symptoms but with different underlying mechanisms. Two other articles tackle the important question of psychiatric symptoms among older adults and their association with cognitive deficits. In a study of nearly 2,000 older community-dwelling elders who were followed for 5 years, those with moderately high level of depressive symptoms or those with low but increasing level of symptoms had persistently worse cognitive function. 3 The authors’ approach allows us to consider the fluctuating course of depressive symptoms and how these trajectories may be superimposed on other central nervous system functions, in this case, cognition. This fascinating interplay needs to be understood further, given how often both depressive symptoms and cognitive impairment occur in aging populations. The relationship between depression and cognitive functioning in aging is complex, with different temporal associations between depressive symptoms and the onset of cognitive decline and dementia. Some studies suggest older adults may develop depressive symptoms in reaction to experiencing cognitive decline, whereas others have identified depression as a risk factor for dementia. 4 It has also been proposed that depressive symptoms and cogni