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IB DP Psychology — Biological Approach | SL & HL | Paper 2 (Health & Well-Being Option)
🎯 Learning Intentions By the end of this note, you will be able to:
- Define mental health disorder, neurotransmitter imbalance, and genetic vulnerability using IB-aligned terminology.
- Explain how neurotransmitter dysregulation contributes to the development of mental health disorders such as depression and anxiety.
- Describe the role of genetic factors, including heritability and gene–environment interaction, in predisposing individuals to mental health disorders.
- Explain how structural and functional brain abnormalities are associated with mental health disorders.
- Evaluate research evidence for biological explanations of mental health disorders using supporting and opposing studies in ACAS format.
- Apply biological explanations to a realistic case study from the health and well-being context.
- Discuss the extent to which biological factors alone provide a complete explanation of mental health disorders.
- Analyse biological explanations using relevant concept areas: Causality, Perspective, Bias, and Responsibility.
Introduction & Context
Imagine two people who experience the same stressful life event — perhaps the loss of a job or the breakdown of a relationship. One person feels sad for a few weeks and gradually recovers. The other spirals into a prolonged state of hopelessness, loses interest in activities they once loved, struggles to sleep, and finds it almost impossible to function at work or in relationships. Both faced the same external trigger, yet their responses were dramatically different. Why?
This question sits at the heart of mental health research. For much of human history, mental health disorders were explained through spiritual, moral, or purely psychological frameworks. Over the last century, however, advances in neuroscience, genetics, and brain imaging have revealed that the brain itself — its chemistry, its structure, and its inherited architecture — plays a profound role in shaping psychological vulnerability. The biological approach argues that mental health disorders are not simply the result of difficult life experiences or faulty thinking patterns, but are rooted in measurable physical processes within the body and brain.
Understanding these biological mechanisms does not mean dismissing the role of experience or environment. Rather, it means recognising that the brain is a biological organ, and like any organ, it can malfunction in ways that produce psychological distress. This note explores three major biological explanations: neurotransmitter dysregulation, genetic factors, and brain structure and function.
🔧 Analogy — The Faulty Thermostat Think of the brain's chemical systems like a thermostat regulating the temperature of a house. When the thermostat is calibrated correctly, the house stays comfortable regardless of the weather outside. But if the thermostat is faulty — either too sensitive or not sensitive enough — the house becomes uncomfortably hot or cold even when external conditions are perfectly normal. In the same way, a brain with dysregulated neurotransmitter systems may generate intense emotional distress even in the absence of any obvious external cause. The "fault" is internal, not environmental.
Core Concepts
Before exploring specific mechanisms, it is worth establishing what we mean by a mental health disorder from a biological standpoint. When psychologists and psychiatrists classify disorders, they look for patterns of thought, emotion, and behaviour that are persistent, distressing, and that impair everyday functioning. The biological approach adds a further claim: that these patterns are underpinned by identifiable physical abnormalities in the brain or body.
📖 Key Definition — Mental Health Disorder (Biological View) From a biological perspective, a mental health disorder is a clinically significant pattern of psychological symptoms — such as persistent low mood, disordered thinking, or extreme anxiety — that is associated with measurable abnormalities in brain