Biological Explanation of Schizophrenia (OCR GCSE Psychology): Revision Note

The dopamine hypothesis

• The dopamine hypothesis is a biological explanation of schizophrenia

• It assumes the disorder has a biological basis due to abnormalities in:

  • brain structure

  • brain function

  • neurotransmitter activity

• These abnormalities may result from genetic vulnerability, making some individuals more likely to develop schizophrenia

Key ideas

• Schizophrenia is linked to overactivity in the dopamine system

  • Dopamine is a neurotransmitter involved in movement, attention, emotion, and perception

• Dopaminergic neurons transmit dopamine across synapses (gaps between neurons)

• In schizophrenia:

  • these neurons fire too often or too easily, causing excess dopamine release

  • dopamine receptors (particularly D2 receptors) become overstimulated

  • brain messages become confused or exaggerated

• As a result, this can lead to:

  • hallucinations – hearing or seeing things that aren’t there

  • delusions – false beliefs or paranoia

  • disorganised thinking and speech

• Research shows that people with schizophrenia tend to have more dopamine receptors in certain brain areas

• This leads to more frequent neuron firing supporting the link between dopamine imbalance and positive symptoms of schizophrenia

Brain structure & function

• Brain scans show that the brains of people with schizophrenia often look different from those without the disorder

• Abnormalities in brain structure and function are linked to symptoms and behaviours

Frontal lobes

• The frontal cortex acts as the brain’s 'control centre', responsible for:

  • planning

  • decision-making

  • self-regulation

• People with schizophrenia show:

  • reduced blood flow and lower activity in the frontal cortex

  • impaired judgement and disorganised thinking

  • a smaller or less active prefrontal cortex, leading to poor logical and goal-directed behaviour

Temporal lobes

• The temporal lobes are involved in processing auditory information and understanding speech

• In schizophrenia studies show:

  • reduced volume in these areas

  • symptoms such as auditory hallucinations, where individuals hear voices that are not real

Hippocampus

• The hippocampus, which helps form new memories and regulates emotion

• In schizophrenia, research shows:

  • a smaller hippocampus

  • the more severe the symptoms, the greater the hippocampal shrinkage

• This is associated with:

  • memory problems

  • emotional instability

  • difficulty distinguishing between reality and imagination

Neurological damage

• Some researchers believe that neurological damage may occur before birth, when the brain is still developing

• Infections, lack of oxygen, or complications during pregnancy or birth can damage brain cells and affect normal brain development

• This early damage increases a person’s vulnerability to schizophrenia later in life

• The effects may not appear until adolescence or early adulthood, when the affected brain areas become fully active

Criticisms of the biological explanation

• Ignores the role of nurture

  • The theory focuses mainly on biological causes (nature) and neglects environmental or psychological factors such as stress, trauma, or family conflict (nurture)

  • Schizophrenia may result from an interaction between biology and environment, not biology alone

• Cause and effect problem

  • Brain dysfunction might be a result of schizophrenia rather than the cause

  • Many studies rely on post-mortems or brain scans after diagnosis, so it’s unclear whether brain changes existed beforehand

• Deterministic

  • The theory implies that people have no control over their symptoms, as behaviour is seen as entirely caused by brain activity

  • This view is pessimistic and ignores personal responsibility or free will

• Reductionist

  • It oversimplifies a complex disorder by reducing it to brain chemicals or structure alone

  • Psychological and social factors likely interact with biology to produce symptoms

• 'Schizophrenia’ as too broad a label

  • Some psychologists argue that schizophrenia covers a wide range of symptoms

  • It may be unrealistic to look for one single biological cause for such a varied disorder