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Mental illness is common, complex, and costly. One person in every eight, a total of 970 million people worldwide, live with a mental disorder. Anxiety and depressive disorders are the most common conditions. Most of those affected do not have access to effective care, according to the World Health Organization.
In addition to the profound human costs, social exclusion, and missed life opportunities, the economic burden of mental illness is estimated at approximately US $ 5 trillion annually.
Psychiatry is the branch of medicine that is primarily concerned with the treatment and study of mental illness. Terminology changes over time, but a ‘mental illness’ is a condition that is characterised by a clinically significant disturbance of thinking, emotional regulation, or behaviour. Recurrent depressive disorder, for example, can present with low mood, negative thoughts, poor sleep, and feelings of hopelessness.
The tasks of psychiatry are to (a) increase awareness of the symptoms of mental illness (in order to reassure most people that they are not mentally ill and to facilitate early assessment for those who might be); (b) provide treatment and support to people with mental illness and their families (including psychotherapy, medications, and social support), and (c) study mental illness in a systematic way, so as to better understand causes, treatments, and prevention, and better protect the human rights of those affected.
Diagnosing mental illness
How to diagnose specific mental illnesses, and to what extent it is useful to do so, have been topics of debate throughout the history of psychiatry and are still discussed today. Diagnosis in psychiatry is largely based on symptoms. For depression, these symptoms can include depressed mood, lack of enjoyment, poor appetite, and feelings of helplessness.
The symptom-based diagnostic systems most commonly used are the World Health Organization’s ICD-11: International Classification of Diseases (Eleventh Revision) (ICD) and the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) (DSM). Both of these publications list common clusters of symptoms that characterise various mental illnesses.
Diagnoses based on these classification systems do not necessarily map onto biological conditions. These diagnoses provide links between symptoms on the one hand, and understanding and treatment on the other hand. They are tools and guides, rather than ends in themselves. They can always change.
Used wisely, diagnostic systems such as ICD and DSM create a common language for sharing experiences of mental illness, psychiatric symptoms, and psychological suffering. They also facilitate the study of the causes of, and treatments for, specific collections of symptoms or mental illnesses.
Clear, published diagnostic systems bring clarity and accountability to the diagnosis of mental illness and psychiatric treatment. In this way, diagnostic systems can help protect human rights, especially in the rare context of admission and treatment without consent under mental health legislation. Risks of diagnostic systems include over-literal interpretation of criteria in individual cases, diagnostic expansion in order to access services, and general lack of flexibility. These should be avoided.
Other potential benefits of diagnostic systems, once they are used thoughtfully, include reducing stigma, alleviating disproportionate guilt or blame that individuals or families might feel, helping create networks of people affected by similar symptoms, and assisting people in choosing the best treatments.
Ultimately, DSM, ICD, and other classification systems have important uses and essential roles, but there is no single way of understanding that makes sense for everyone all the time. Diagnoses need to be applied and considered in the context of each individual’s life, and used as tools for building a shared understanding, rather than rigid categorisation.
Diagnosis also guides towards treatment. We know that interventions such as psychotherapies (talking therapy), antidepressant medication, and antipsychotic medication are very effective for many mental illnesses.
There is still much improvement to be made in mental health services, but there is a great deal that we can do now – and even more progress that we can make in the future.
Brendan Kelly is Professor of Psychiatry at Trinity College Dublin. This is an edited extract from his new book, “The Modern Psychiatrist’s Guide to Contemporary Practice: Discussion, Dissent, and Debate in Mental Health Care”, which is available online free of charge: https://www.taylorfrancis.com/books/oa-mono/10.4324/9781003378495/modern-psychiatrist-guide-contemporary-practice-brendan-kelly