Psychiatric diagnoses continue to lack the predictive power required of hard science. A new framework is needed to understand mental health, distress and disease
The American Psychiatric Association (APA) will release the fifth edition of its Diagnostic and Statistical Manual (DSM-5) in May 2013. DSM-5 has been years in the making. The process included planning sessions, international research conferences, review of literature, a series of monographs, secondary analysis of data and field trials involving hundreds of scientists and clinicians, drawn from many countries and disciplines, and feedback from the public. Many interest groups — neurologists, psychologists, insurance and pharmaceutical industries, legal and forensic fraternity, military veterans and anti-psychiatry groups — have been watching the process and outcome closely as the DSM has a wide impact. The Indian Psychiatric Society also submitted its views to the APA.
The DSM-5 has pursued the basic framework adopted by its forerunners, DSM-III and its successors DSM III R, IV and IV TR. DSM III, with its atheoretical approach, objective diagnostic criteria and specific exclusions, was revolutionary at the time of its introduction in 1980. Its focus on standardised diagnosis and on improving inter-rater reliability had a major impact on psychiatric practice and research. It soon became the international standard.
The absence of laboratory tests to diagnose mental disorders forced psychiatry to focus on clinical presentations for this purpose. The lack of pathognomonic symptoms required the discipline to rely on identifying collections of symptoms to define clinical syndromes. Psychiatric classifications include medical conditions (e.g. delirium, dementia and psychiatric manifestations of medical diseases), severe mental disorders (schizophrenia, bipolar disorders, psychotic depression, and stupor) and stress-related conditions (e.g. depression, anxiety and adjustment disorders).
The DSM laid out objective criteria for diagnosis. It offered differential diagnosis in order to distinguish similar conditions. It allowed psychiatrists working around the globe to read from the same page. It facilitated collaboration and comparison. It improved communication, standardised research, increased, and improved the evidence base. A unified language also helped mental health activism.
Despite major advances and significant progress, the DSM has many critics. Most detractors are free with their criticism, without providing comprehensive solutions to the complex issues facing people with mental illness. Defining mental illness is no simple task. A single definition to partition health, illness and disease has proved to be extraordinarily difficult. The diversity of and heterogeneity within these conditions are major challenges. Typically, patients emphasise distress and suffering, while psychiatrists diagnose and treat “diseases.” Mental disorders include both disease and illness. Nevertheless, diagnostic criteria for psychiatric disorders did not bridge the classical disease-illness divide between physicians’ perspectives and patients’ subjective experience of sickness. In fact, the DSM resulted in language, concepts and frameworks, which contrasted starkly with those held by patients, impeding understanding of the illness experience and diminishing the role of patient narratives. In addition, DSM could not overcome the fact that different etiology and pathology can result in similar clinical presentations, and that a particular cause can produce diverse clinical manifestations. Research and specialist interests also increased manifold the number of diagnostic categories.
Little regard for context
The difficulty in separating disease from distress is a major challenge. The DSM system emphasised symptom counts to identify psychiatric categories, with little regard for the context (e.g. psychosocial stress, personality, and coping). This strategy improves reliability of diagnosis for non-psychotic conditions associated with psychosocial adversity, but also includes people with normal responses to such difficulties. Psychiatry tends to reify diagnosis, making abstract concepts concrete. Psychiatric practice transmutes clinical syndromes (collection of symptoms) into diseases.
The DSM III also suppressed etiological debates about mental disorders and placed them on the back burner. The biomedical model, which undergirds the approach, became dominant, annihilating psychological, behavioural and social conceptualisations. However, the APA argued that reliable diagnoses would result in the recognition of underlying neurobiological substrates and facilitate etiological research; it would lead to the development of new and more effective treatments.
However, the frequent revisions of the DSM, with minor changes often based on limited evidence, also prompted debates on the motivation of the APA. The numerous minor and major disagreements with World Health Organisation’s International Classification of Diseases (ICD) -10 diagnostic categories supported the argument that most changes were arbitrary as there was no agreement among international experts. The DSM had to contend with many charges including medicalising normal reactions, lowering diagnostic thresholds to create spurious “epidemics,” creating new categories without evidence, using medication responses to define categories and playing into the hands of the pharmaceutical industry.
Challenges to diagnosis
Defenders of the DSM argue that its primary purpose is to enable psychiatrists to reliably identify individuals who seek clinical attention, and to facilitate communication among clinicians and researchers. The field of psychiatry has to grapple with the current state of knowledge with its inherent limitations. The lack of laboratory diagnosis, poor understanding of genetic basis and psychological vulnerability, and the need to provide categorical diagnosis for phenomena which lie along a spectrum (e.g. depression, anxiety, cognitive impairment and substance misuse) are difficult challenges.
The most ardent supporters of the DSM acknowledge its imperfections but argue that it reflects our current understanding and state of the science. They contend that DSM-5 is not an attempt to define normal and that being normal is not the same as not having a DSM-5 diagnosis. They argue that having a psychiatric diagnosis is not the same as being insane or crazy, stigmatising labels, which do not apply to the vast majority of people with a DSM diagnosis. They suggest that prescribing medication for any condition in preference to time and labour-intensive psychological interventions is dependent on many factors, including the economic realities of medical practice, and does not necessarily imply medicalising normality.
Pressure from user groups
The use of a single set of criteria, useful to psychiatrists working in specialist settings, in other locations (e.g. definitions for legal use and for reimbursement, in primary care and across cultures) is not without problems. There was also pressure from patient and user groups, as any changes to the DSM-IV categories in the new revision would have affected their claims for disability support and health insurance. Consequently, there were demands to enlarge and to reduce the diagnostic net from different quarters.
A close examination of the DSM-5 suggests the maintenance of status quo. Psychiatric diagnoses and theories, with their technical language, operational criteria, elaborate classificatory systems and empirical data continue to lack the predictive power required of hard science. Its diagnostic systems and models do not explain many aspects of mental health and illness. Human cognition, emotion and behaviour are complex, interconnected and under a variety of influences (e.g. genetics and biology, psychological, social and cultural forces), whose effects cannot be teased out under controlled experimental conditions.
Nevertheless, psychiatric treatments help millions of people lead productive lives. The DSM process and consultation was elaborate and transparent, seeking opinions and evidence from people with diverse backgrounds. Despite its shortcomings, it does reflect the current state of the science. Psychiatry, at this moment in time, has been compared to biology before Darwin and astronomy before Copernicus.
Thomas Kuhn in his book The Structure of Scientific Revolutions described three stages: (i) normal science (routine scientific work) within existing paradigms and a dedication to solving puzzles, (ii) serious anomalies produced by research, which leads to a crisis, and finally (iii) resolution of the crisis by the creation of a new paradigm. Psychiatry today, with its attempt at solving the clinical puzzles and its many anomalies, is awaiting a paradigm shift, which will not only clarify these complex issues but will also provide for a new framework, insight and understanding. Psychiatric research, despite its current attempts at testable conjectures and refutations, is still within a paradigm that seems inadequate for the complexity of the task. Psychiatry awaits its new dawn.
(Professor K.S. Jacob is on the faculty of the Christian Medical College, Vellore. The views expressed are personal)