最後更新日期 六月 25, 2021.
Diagnosis is an essential procedure in mental health as it helps clinicians determine appropriate treatments for patients. However, unlike other medical conditions, patients with mental disorders often may not show any physical signs, nor are there any objective laboratory or radiological investigations that can be performed to confer a diagnosis. In case you ever wonder, here’s how mental health professionals diagnose patients and the tools they use.
How is a mental health diagnosis carried out?
Diagnosis refers to “the identification and classification of abnormal behavior” and is made based on information related to the patient’s mental disorders including:
- Patient’s reported symptoms
- Observation of patient’s speech and behaviour
- Objective clinical assessments
- Information from family members
Psychiatrists may also use a combination of physical examination, laboratory and radiological tests and other psychometric assessments to evaluate a patient’s condition and make a formal diagnosis.
Diagnostic manuals are like handbooks for clinicians to perform diagnosis. Mental health professionals take reference from the classification systems and tools in the manuals and match them with the assessments’ results. From depression, anxiety, obsessive-compulsive disorder, to post-traumatic stress disorder and bipolar disorder, many common mental disorders can be diagnosed with the help of diagnostic manuals. Overall, the primary goal of diagnosis is to decide on a treatment approach.
How exactly are normal and abnormal defined?
Mental health professionals need to distinguish “normality” from “abnormality”, in order to identify “abnormal behavior” which may hint the presence of mental illnesses. One way of defining normal versus abnormal is to use a statistical approach, describing the occurrence of phenomenon using a bell-shaped curve (see below), also known as normal distribution in statistics. Normality falls on the middle range of the curve and conforms to social norms and rules of society. In contrast, those who exhibit a degree of abnormality may deviate from the middle range of normal distribution and demonstrate unusual and deviant behavior.
In other circumstances, mental health professionals may define normality based on the reaction to circumstances in life. If the reaction appears to be more serious or lasts longer than what is expected in the general population, then a mental illness may be suspected.
What is DSM-5?
The DSM-5 is one of the most representative diagnostic manuals employed by mental health professionals all over the world. DSM stands for The Diagnostic and Statistical Manual of Mental Disorders, where the number “5” indicates that it is currently in its fifth edition. This latest version was published by the American Psychiatric Association (APA) in May 2013 and has earned recognition in psychiatrists, psychologists and other health care professionals across America and Western cultures.
What is included in the DSM-5?
The DSM-5 currently includes approximately 300 mental illnesses and a list of symptoms for mental health professionals to refer to when diagnosing patients with abnormal mental health conditions. It contains descriptions, symptoms and other criteria for the diagnosis of mental disorders. However, the DSM-5 does not list possible causes of the mental disorders but only descriptively presents the symptoms.
Why are the DSM-5 commonly used?
Published by the American Psychiatric Association, the DSM-5 is considered as an authoritative guide to the diagnosis of mental disorders, frequently reviewed and updated since the first version came out in 1952. It provides a common language for clinicians to communicate and diagnose their patients. Outside the clinical setting, the manual has also been used extensively for research purposes in the academic field.
What is the ICD?
Also an internationally recognized standard for diagnosing mental disorders, the International Classification of Diseases, or in short ICD, is developed by the World Health Organization (WHO). The manual is currently in its tenth edition, but will soon be replaced by ICD-11, which will come into effect from January 1, 2022. The first version of the ICD dated back to 1948 and was initially designed to document all diseases and health conditions, physical and mental, for both clinical and research purposes. Its codes for conditions are adopted by the health insurance industry for identification of conditions. Special attention is given to primary care and low to middle income countries.
What is the CCMD?
Taking cultural influences into consideration, the Chinese Society of Psychiatry (CSP) has established the Chinese Classification of Mental Disorders (CCMD) specifically for diagnosis of mental disorders in the Chinese cultural background. The CCMD is recently in its third edition, released in 2001.
Despite the similarities shared with the DSM and the ICD, the CCMD also contains information for culture-specific syndromes in the Chinese and Asian cultures, such as Neurasthenia (Chinese: 神經衰弱; a syndrome marked by physical and mental fatigue accompanied by withdrawal and depression) and Zou Huo Ru Mo (Chinese: 走火入魔), where mental disorder patients are often characterized by “having low spirit.” However, this classification system is not widely used outside of China.
Importance of achieving reliability and validity
Apart from normality and abnormality, two critical concepts to be maintained strictly by clinicians in diagnosis are reliability and validity.
Reliability of diagnosis
Reliability refers to whether the diagnosis is consistent when the same diagnostic procedure is used over and over again. Clinicians can improve the reliability of diagnosis by using standardized clinical interview schedules. One challenge to maintain reliability is that diagnosis involves the subjective interpretation by the clinician to determine the severity of the patient’s symptoms. Nonetheless, diagnostic manuals like the DSM-5 and ICD have set up a universal standard for mental health professionals to take reference from and improve diagnosis reliability.
Validity of diagnosis
Validity is the term used to describe how well a diagnosis is indicating what is being measured. A high validity in the diagnostic criteria means that the diagnostic criteria truly describes what is expected of a patient suffering from an illness, and is crucial for patients to receive the appropriate treatments and a correct prognosis. Unlike diagnosis for physical disorders, it is more challenging to accurately diagnose psychological disorders as clinicians cannot rely on other objective indicators.
Other factors influencing diagnosis
Use of classification systems
Over time, there have also been changes in the diagnostic manuals. Taking DSM-5 as an example, recent changes include:
- Renaming gender identity disorder into gender dysphoria
- Addition of hoarding disorder
- Incorporation of various types of autstic disorders, such as Asperger’s Syndrome, into the autism spectrum disorder category
- Addition of premenstrual dysphoric disorder
The way mental health professionals make diagnoses in the Western and Asian cultures may differ. Clients with different cultural backgrounds may have different attitudes towards mental illnesses, influencing how they report or exhibit their symptoms. Moreover, culture-specific syndromes are difficult to diagnose and recognize if the diagnostic manual used does not cover the syndromes. For example, mental health professionals cannot diagnose a patient with Neurasthenia with the use of the DSM but the CCMD.
Biases that arise in the diagnostic process may reduce the validity and accuracy of the diagnostic process. For instance, clinicians influenced by confirmation bias (a tendency to interpret information in a way that confirms their beliefs or assumptions) may misjudge a patient’s condition, particularly when clinicians have not collected sufficient and comprehensive information about the patient. Other biases may be associated with the physical appearance, age, ethnicity, gender or other characteristics of the patient.
False classification of normality and abnormality could lead to undesirable and unethical outcomes. If an inaccurate diagnosis is made to a healthy person and results in unnecessary treatment procedures, it may bring great distress to the “patient” and the family, stirring up stigmas and prejudices against them. Vice versa, making an incorrect diagnosis may delay necessary treatments given to patients and in the worst case, aggravate the symptoms and hardships they are facing.
Can I diagnose myself using diagnostic manuals?
While diagnostic manuals like the DSM-5, the ICD and the CCMD are all essential tools in psychiatric diagnosis, people without professional training and relevant experience are not recommended to diagnose themselves or others. Diagnostic manuals are written with jargons and professional terminologies for trained and qualified professionals in order to formulate appropriate treatments for patients. If you suspect yourself or others having a mental disorder, seek advice from a professional mental health practitioner as soon as possible and do not rely on self-diagnosis using diagnostic manuals.