hallucinations. This is also the case with depression in that some individuals report different types of depressive symptoms than others. This suggests to some researchers that there might be different underlying brain processes involved in these variations. What now is considered as a single disorder may be better represented as separate disorders based on underlying mechanisms. Further, certain mental disorders also show gender differences. For example, females tend to develop schizophrenia later than males, but both males and females show similar rates of the disorder. However, females do show higher rates of mood and anxiety disorders.
Overall, neuroscience methods may lead to better diagnostic procedures as well as understanding the mechanisms of the disorder. For example, genetic research suggests similarities between schizophrenia and bipolar disorder in terms of the genes involved. It is also possible to use neuroscience techniques to follow the course of a disorder over time. One study (Raj, Kuceyeski, & Weiner, 2012) based on brain imaging methods suggests that neurocognitive disorders follow specific pathways in the brain. Another potential for neuroscience methods is that by knowing the underlying brain and genetic processes involved in a particular disorder for a particular person, it would be possible to create a treatment that is designed specifically for that individual.
The potential for using neuroscience approaches to classify mental illness and inform its treatment is an important one.
National Institute of Mental Health
Concept Check
For each of the following types of assessment, what kinds of information can you obtain from it and what is one example of it?Symptom questionnairePersonality testProjective testNeuropsychological testNeuroscience technique
Diagnostic Considerations in Psychopathology
Over the past 100 years, there have been a variety of debates on how to diagnose and classify mental disorders. In the past 50 years, the emphasis has been on reliability of diagnosis such that mental health professionals in one location would diagnose the same individual in the same manner as professionals in another location. As part of this emphasis, there has been a push for observable characteristics that would define a specific disorder. Such characteristics as depressed mood over the day, diminished interest in activities, weight loss, insomnia, fatigue, feelings of worthlessness, difficulty thinking, and thoughts of suicide would be considered in the diagnosis of depression. These types of criteria make up the structure of the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association (APA), and the International Classification of Diseases (ICD), published by the World Health Organization (WHO). The DSM is used in North America, whereas the ICD is used in Europe. In general, the criteria used in the DSM and ICD are signs and symptoms that are delineated through observation of, and conversation with, the individual.
Diagnostic and Statistical Manual of Mental Disorders (DSM): a publication of criteria for diagnosis by the American Psychiatric Association (APA), used in North America
International Classification of Diseases (ICD): a publication of criteria for diagnosis by the World Health Organization (WHO), used in Europe
Categorical Versus Dimensional Approaches
The historical considerations of psychopathology emphasized careful observation and interaction with the afflicted individuals as important methods for understanding the nature of the disorder. Based on these observations of symptoms and signs, individuals were diagnosed and classified as falling into discrete categories of disorders. This is an important level of analysis and one I will emphasize throughout this book. However, there are other levels of analysis for understanding psychopathology.
With progress in the neurosciences in general and brain imaging and genetics in particular, other levels of analysis have become possible. These new levels of analysis offer different perspectives for the field of mental illness. What seemed like discrete categories of psychopathology previously are now seen to cluster in new and different ways when considered from the standpoint of genetics. Additional groupings have emerged as scientists have considered the neural networks involved in particular manifestations of psychopathology. This has led to the realization that mental disorders can be described in both a categorical and a dimensional manner.
categorical: in psychopathology, describes the approach to determining whether a person has or does not have a disorder based on the presence or absence of a certain set of symptoms
dimensional: in psychopathology, describes the assessment of severity of a disorder on a continuum, in terms of differing degrees
As shown in the physical sciences, there are times in which a phenomenon can be described both categorically and dimensionally. For example, when water is heated, the rise in temperature can be described in a dimensional manner in terms of a certain number of degrees. However, at a critical point, the water turns to steam, which is a categorically different state from water. Likewise, a reduction in temperature changes water into a different categorical state—ice. The question for the study of psychopathological disorders is to determine the underlying dimensional changes that are associated with categorical-like transformations leading to a disordered state. Further, different underlying processes may actually allow for the presence of more than one disordered state at the same time.
Comorbidity, Internalizing Disorders, and Externalizing Disorders
Technically, when an individual is seen to have more than one disorder at the same time, the disorders are referred to as comorbid. In the National Comorbidity Survey, a large number of individuals with one disorder were found to have one or more additional diagnoses (Kessler et al., 1994). For example, individuals with generalized anxiety disorder will often also show symptoms of depression. Further, these two disorders have overlapping genetic and environmental risk factors (Kendler, Neale, Kessler, Heath, & Eaves, 1992). The number of diagnoses found in the National Comorbidity Survey was associated with the severity of the symptoms. This has suggested to researchers that there exists a general underlying vulnerability to psychopathology that may be independent of the particular symptoms expressed (Pittenger & Etkin, 2008).
comorbid: descriptive term used when an individual has more than one disorder at the same time
internalizing disorders: disorders that are experienced internally such as anxiety and depression
externalizing disorders: disorders that are manifested in the external world by the person’s behavior, such as conduct disorder (CD), antisocial personality disorder, and other behavior-based disorders
A related approach is to consider which disorders co-occur with one another. In general, two clusters have been found. The first is referred to as internalizing disorders. The focus of these disorders is the inner world of the person, and they include anxiety and depression. The second cluster is referred to as externalizing disorders. The behavioral focus of these disorders is the external environment of the person. These disorders include conduct disorder, oppositional defiant disorder, antisocial personality disorder, substance use disorder, and in some studies attention deficit/hyperactivity disorder (ADHD). These studies of comorbidity clusters have led scientists to search for common factors such as genetics, brain processes, and environmental risk profiles that might be associated with each cluster. Overall, research has supported the idea that mental disorders can be clustered and
