Classification of Psychological Disorders

Why Classification Matters

Before we can study psychological disorders, we need a way to organise them. A classification system is simply a list of categories — each category groups together specific disorders that share certain features. Without such a system, a psychologist in Delhi and a psychiatrist in Mumbai might use different names for the same condition, making communication impossible. Classification also helps researchers figure out what causes a disorder and how it develops and persists over time.

The Two Major Classification Systems

Two official manuals are used worldwide to classify psychological disorders. The first is published by the American Psychiatric Association (APA). Its current edition is the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, commonly called DSM-5. DSM-5 provides clear, specific clinical criteria — a checklist of symptoms — that tell a clinician whether a particular disorder is present or absent.

The second system is the one officially used in India and many other countries: the International Classification of Diseases, 10th Revision (ICD-10). Specifically, the section dealing with mental disorders is called the ICD-10 Classification of Behavioural and Mental Disorders. It was prepared by the World Health Organisation (WHO). For every disorder, ICD-10 gives a description of the main clinical features (the core symptoms), along with other associated features and diagnostic guidelines to help in making a correct diagnosis.

What a Classification Includes

Both manuals work in a similar way. For each disorder, they list:

• The main clinical features or symptoms that define the disorder.
• Associated features — other signs that often accompany the disorder but are not required for diagnosis.
• Diagnostic guidelines — practical rules to help a clinician decide whether a person meets the criteria for that disorder.

A Note on Context: When Is Behaviour Abnormal?

The textbook gives a simple activity to drive home an important point. Eating sand would normally be considered abnormal behaviour. But if a person is stranded on a beach after a plane crash and has no food, eating sand becomes a normal survival response. Similarly: …