Chapter 15: Varieties of Abnormal Behaviour

Historically, mental health professionals distinguished between organic disorders with clear physical origins and functional disorders without obvious physiological causes, alongside the major division between neurosis—where a patient maintains reality contact—and psychosis, which involves a profound distortion of reality and personality. While traditional systems like those developed by the American Psychiatric Association categorized illnesses similarly to general medicine, researchers now question this "medical model" due to the significant overlap between symptoms and the fact that many disorders represent extreme variations of normal personality traits rather than discrete diseases. Empirical techniques like factor analysis have revolutionized this field, providing evidence that conditions once thought to be related, such as neurotic and psychotic depression, are actually independent clinical entities. Furthermore, objective performance tests and genetic studies support the theory that psychosis and neurosis exist on separate dimensions rather than a single continuum of severity. Physiological assessments, including sedation thresholds and visual after-effect tests, offer additional tools to differentiate between complex states like anxiety and hysteria or various forms of schizophrenia. The chapter advocates for a "dimensional approach" to diagnosis, particularly the model emphasizing psychoticism, neuroticism, and the introversion-extroversion spectrum. This shift away from rigid categories allows for a more nuanced understanding of "mixed" disorders and facilitates targeted treatment strategies. By linking a patient's unique personality profile to specific therapeutic interventions—such as systematic desensitization for phobias or tailored pharmaceutical choices—the modern psychological approach aims to bridge the gap between diagnosis, cause, and effective clinical outcomes.