Proposal for New Classification Model of Psychiatric Disorders Michael Levin, M.D., M.S. (Pharmacology) Abstract Psychiatry lags behind other medical fields in the diagnosis and classification of disorders. While other medical specialties came up with reasonably cohesive nomenclature and organization, mental disorders remain in apparent disarray. The proposed classification model approaches psychiatric disorders using the logic that guided the classification of medical diseases. Brain is not one organ and its disorders should not be viewed either through differential diagnosis (reserved for one organ diseases) or as creative labeling of various combination. Instead, we need a classification based on underlying psychobiology which in many cases is shared by seemingly unrelated entities. AMPERIC model is an attempt to approach psychiatric disorders in a sensible and practical way. The model organizes and directs treatment option toward intrinsic psychobiological pathology of the disorders and helps in bridging the gap between psychopharmacological and psychotherapeutic interventions. Content Introduction Part I Review of Systems Part II Disorders of First Order (pathology limited to one system) Part III Disorders of Second Order (two systems disorders) Part IV Disorders of more than two systems Part V DSM Disorders not belonging to classification Conclusion and additional considerations References Introduction Current DSM (1) classification exemplifies nosological chaos in psychiatry. It lacks a unifying theme and fails to resolve conflicts among competing theories. Instead of connecting, it wedges between the disorders and their treatment. Notwithstanding the caution not to assume “each category of mental disorder … [as] a completely discrete entity with absolute boundaries” and not to utilize it “in a cookbook fashion”, the manual is used in a precise manner against which it carefully advises. Detailed criticism of the DSM classification deserves a separate forum, but it's imperative to recognize that existing taxonomy doesn‟t serve the needs of practitioners and researchers alike. Steadily, we are developing a better understanding of mental disorders. Neuropsychological, genetic, and psychiatric research data are strong. Neuroimaging techniques offer objective tools to investigate the diseases and lead the way to a new classification model. Reducing mental disorders to components Our brain is a collection of integrated systems, or modules, each with intricate functional responsibilities. Complex behaviors and psychiatric disorders can and should be broken down into comprising parts. The new model is based on the premise that various psychiatric disorders share common physiological and pathological pathways. "Pathognomonic" psychiatric symptoms are not tied to a single diagnostic entity. Unique symptom combinations, however, make specific diagnoses. The proposed model identifies seven key modules. Evidently, there are more functional systems in the human brain. The seven, however, form the majority of psychiatric disorders, as either abnormalities of one or more systems or as uncompensated mismatch between the systems. For convenience, the modules are listed under an acronym, AMPERIC, which stands for Arousal system Mood and reward system Perseveration system Executive function system, also referred to as Executive Function Network (EFN) Reality testing system Interpersonal (social) skills system Cognitive (information processing) skills Part I Review of Systems This section describes the systems in their natural, physiological – in contrast to pathological – states. The division doesn't imply simplicity of individual components. Each system is regulated by a multitude of subsystems and neurotransmitters to perform as a sum of all influences. Arousal System Arousal (also referred to as alertness or vigilance) is not limited to wakefulness. Regulation of arousal is essential for survival as well as for daily tasks. Insufficient arousal turns predators into pray, and persistently high arousal is wasteful. In addition, it is advantageous for arousal to rise quickly from the baseline in case of danger and decrease rapidly when the alarm proves to be false or resolved. Anything short of that would be unsafe and imprudent. Arousal is regulated by several complex structures which include amygdalae, thalamus, orbitofrontal and ventromedial PFC and others. (2) While tightly connected to the limbic system and often described as parts of it, mood and arousal are semi-autonomous and can act independently. Arousal is affected by situations and chemicals. In a natural setting, omnipresent caffeine increases it for a short duration, moderate doses of alcohol have the opposite effect. Mood and Reward System Mood is the state of feelings – high and low, joy and sadness. There is a distinction between mood and emotion: mood refers to one‟s state of mind over period of time and is unfocused, while emotions are short-lived and in reaction to recent events. The role of this system is to determine emotional significance of an event, then generate and regulate an appropriate emotional response. (3) The Limbic system is a regulator of emotions. It includes the hippocampus, amygdalae, anterior thalamic nuclei, and limbic cortex (mostly cingulate cortex), and also mammillary body, dentate gyrus, nucleus accumbens, etc. (4) (5) The reward system consisting of anterior cingulate cortex, basal forebrain, amygdalae, ending at nucleus accumbens and the "disgust" system, which ends at insula, play critical roles in motivational drive and psychopathology of some disorders (e.g. antisocial behavior, substances abuse, paraphilias, obsessive disorders, bulimia, etc.) Perseverations and Repetition Stereotypy is an essential part of grooming behavior in lower animals and primates and is present across species. Perseveration and repetition might be powerful in attracting attention. It has been pointed out that it is not the loudness of the phone ringing that gets a response but repetition and persistence. (6) Perseveration is essential in developing task automaticity (reduced dependency on complex cognitive processes on common tasks). Basal ganglia, prefrontal cortex, cerebellum, and temporal lobe were suggested to contribute to perseveration and its regulation. Executive Function Executive function regulates and coordinates brain faculties for optimal choices. It consists of several independent facets under one umbrella which includes management of attention (top-down regulation), working memory, impulse control, regulation of arousal and mood, planning and organizational skills, monitoring of complex social and counter-instinctive behaviors, management of motivation and reward- related behaviors. Top-down attention regulation is active process that forces attention to cognitively challenging tasks, not necessarily of one‟s choosing, against competing distracting stimuli. In contrast down-up regulation is more reactive to salient novelty. (7) (8) Anatomically, the executive function is associated with, but not limited to, the prefrontal cortex . (9) One might get an impression that Executive Function Network is one centralized unit controlling all functions. In reality, various tasks are assigned to different parts within the network. Reality Testing For adoptive behavior one needs an accurate representation of the reality. Reality testing (RT) is the method by which we judge the differences between the internal and external worlds. RT is the tool that enables us to separate subjective experiences from objective reality experienced by others. It was suggested that the brain processes multiple inputs and then attempts to connect the information into cohesive narrative. In order to bring "meaning to input", the left brain tends to narrow range of possibilities, while the right brain tends to widen it. (10) In functional individuals these competing tendencies are balanced into a reality check. The ability to generate abstract ideas and mentally test them against possible real scenarios is important tool of advanced brain. When balance is altered, generated images and associations go unchecked leading to words and actions disconnected from reality, perceived by others as weird. Interpersonal, Social Skills We are governed by a multitude of fine social rules of great complexity and consequences. For appropriate social interactions we need to understand other person‟s mind. In other words, we need "mind-reading" skills. Social skills also include ability to adjust behavior to fit in a group. Various interconnected brain parts involved in social interactions (medial prefrontal cortex, anterior cingulate cortex, precuneus, fusiform area, amygdale, as well as superior temporal and parietal cortexes (right temporoparietal junction) are referred to as "the social brain". Most interpersonal interactions are nonverbal and strongly culturally influenced. Cognitive (information processing) skills Cognitive Processing refers to a heterogeneous set of skills for acquisition, processing, storage, retrieval, and production of information. A partial list of these tools includes language skills, auditory and visual processing, memory in many forms, motor skills, and higher cognitive functions. Although each subsystem has specific characteristics and objectives, complex tasks require cooperation and coordination of several tools. Detailed discussion of these systems is outside the scope of this article and can be found in neuropsychological and psychoeducational literature. How