Explain how normality and abnormality are defined, and describe how classification systems such as the DSM are used to diagnose psychological disorders, including the issues this raises

What this dot point is asking

QCAA wants you to explain how psychologists decide what counts as normal or abnormal, describe the standardised systems used to classify and diagnose psychological disorders, and critically evaluate the problems with diagnosis. You should use named approaches, named classification systems and a named study.

The answer

Defining normality and abnormality

There is no single definition of abnormality; psychologists use several complementary approaches, each with limits.

• Statistical infrequency. Behaviour that is statistically rare is abnormal. The problem is that rare can also be desirable (high IQ), and common does not mean healthy.
• Deviation from social norms. Behaviour that violates a society's unwritten rules is abnormal. This is culturally and historically relative, and risks pathologising harmless difference.
• Failure to function adequately. Abnormality is the inability to cope with everyday demands (self-care, work, relationships). This is practical but subjective.
• Deviation from ideal mental health. Jahoda described criteria for ideal functioning such as self-actualisation and accurate perception of reality; by this strict standard almost everyone is abnormal at times.

Because each approach is flawed, clinicians use them together rather than relying on one.

Classification systems

To diagnose consistently, clinicians use standardised manuals.

• The DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, fifth edition), published by the American Psychiatric Association, lists disorders with specific diagnostic criteria. It is the dominant system in research and in Australia.
• The ICD (International Classification of Diseases), published by the World Health Organization, is used worldwide and includes mental as well as physical conditions.

These systems aim to make diagnosis reliable (different clinicians reach the same diagnosis) and to standardise communication, research and treatment.

The biopsychosocial model

Modern diagnosis interprets disorders through the biopsychosocial model, which holds that psychological disorders arise from an interaction of biological factors (genetics, neurochemistry), psychological factors (thoughts, learning, emotion) and social factors (family, culture, stress). This avoids reducing a disorder to a single cause and guides comprehensive treatment.

Issues with diagnosis

Diagnosis is essential but contested.

• Reliability and validity. A diagnosis is reliable if clinicians agree and valid if it identifies a genuine, distinct condition. Some categories show low inter-rater agreement, and high comorbidity (disorders co-occurring) raises questions about whether categories are truly distinct.
• Labelling and stigma. A diagnostic label can become a self-fulfilling prophecy and attract stigma.
• Rosenhan (1973), On being sane in insane places. Healthy pseudopatients gained admission to psychiatric hospitals by reporting a single hallucinated word, then behaved normally. Staff continued to interpret their normal behaviour through the diagnostic label, and none were detected as sane by staff. The study is a powerful critique of the reliability and validity of psychiatric diagnosis and of the power of labels.
• Cultural bias. Definitions of normality vary across cultures, so systems developed in one culture may misdiagnose people from another.

Putting it together for an exam

Name the definitional approaches and their limits, then name the classification system and the biopsychosocial framework, and finish with a critical evaluation citing Rosenhan and the concepts of reliability, validity and labelling.