During the 1950s it was discovered that the blood pressure medication “reserpine” causes depression in some people (Ayd, 1956). Reserpine was found to lower levels of the neurotransmitter norepinephrine in the brain, which suggests that depression may be related to a lowered supply of norepinephrine.

The dopamine hypothesis suggests that dopamine over-activity causes schizophrenia. Dopamine over-activity could happen in one of the following ways:

Abnormal Brain Structure When diagnosing schizophrenia, clinicians make a distinction between positive symptoms and negative symptoms. Positive symptoms involve additions such as hallucinations, delusions and formal thought disorder. These are transient and respond well to medication. Negative symptoms are mental deficiencies such as withdrawal, blunted affect and poverty of speech. Negative symptoms do not respond well to antipsychotic medication. This suggests that there may be different mechanisms responsible for each type of symptom.

Schizophrenia is a psychotic disorder; this means that it involves a loss of contact with reality. Schizophrenia sufferers experience hallucinations (perception of phenomena that do not exist - e.g., hearing voices) and delusions (false beliefs). Schizophrenia sufferers, therefore, often have severe difficulties in functioning.