Dopamine and schizophrenia: what does the dopamine hypothesis propose?

• A. Overactivity of dopaminergic pathways is linked to positive symptoms; antipsychotics reduce this activity by blocking D2 receptors.
• B. Dopamine has no role in schizophrenia.
• C. Serotonin alone explains schizophrenia.
• D. Dopamine only influences movement, not psychosis.

Answer: (A)

The main idea is that positive symptoms of schizophrenia—like delusions and hallucinations—are linked to too much dopamine signaling in the brain, especially in the mesolimbic pathways. When dopamine activity is elevated in these circuits, signals related to perception and thought can become exaggerated, producing psychotic symptoms. Antipsychotic medications work largely by blocking D2 dopamine receptors, which dampens that overactive signaling and helps reduce the positive symptoms. This is supported by evidence that drugs increasing dopamine can trigger psychotic-like experiences, and imaging studies show higher dopamine activity in regions associated with positive symptoms in schizophrenia. It’s not that dopamine plays no role or that only serotonin explains things; rather, dopamine’s influence in these pathways is central to the expression of positive symptoms, and blocking D2 receptors is a key mechanism by which antipsychotics exert their therapeutic effect.