Describe two theories which explain the occurrence of schizophrenia. Explain how these theories relate to the environment and to genetics.
This paper sets out to look at the mental illness of Schizophrenia and will examine two theories on the cause of this disorder and how they relate to genetics and the environment. The two theories we will discuss are, ‘The Dopamine Theory’ and ‘The Genetic Theory’
Schizophrenia is a chronic and disabling brain disorder which is characterized by gross distortion of reality. The name ‘Schizophrenia’ derives from the Greek words skhizein meaning "to split" and Phrenos (phren) meaning "mind” (Taylor, 2011). The condition is categorised by either Positive or Negative Symptoms which are unique to each individual. Individuals suffering from positive symptoms of the disorder experience on-going episodes of psychosis affecting their ability to distinguish, what is real or imagined. Positive symptoms can be defined as symptoms of behaviour that are present but should be absent; they include behaviours such as delusions, hallucinations, fragmented thinking and unusual patterns of speech or behaviour. Negative symptoms on the other hand are the absence of normal behaviours which result in symptoms such as flattened emotional response, inability to express pleasure, apathy, poverty of speech and social withdrawal (Norman, 2004: 365).
Schizophrenia is a very complex disorder, and despite on-going debates, researchers have failed to identify one single cause of the disorder, however, it would appear that the consensus is that both biological and environmental factors could play an important role in the occurrence of the illness.
One of the most well debated theories on the cause of Schizophrenia is the dopamine theory. The dopamine theory postulates that schizophrenia occurs as a result of hyperactivity of the neurotransmitter dopamine in the synapse. There are four main dopamine pathways which have been implicated in the disorder of Schizophrenia and they are; the Nigrostriatal pathway which is involved in motor control, Tuberoinfundibular pathway associated with sensory processes and the Mesolimbic and Mesocortical pathways which are connected to memory, motivation and emotional responses (Stahl, 2002: 10).
Research has given much attention specifically to the mesolimbic pathway which is a brain circuit dependent on dopamine. The mesolimbic pathway is often referred to as the ‘reward pathway’ due to its key role in linking certain behaviours to the sensation of pleasure, such as those associated with the use of psychostimulant drugs like amphetamine, MDMA (Ecstasy) and cocaine (Stahl, 2008: 272). The evidence to support the theory that mesolimbic dopamine plays a role in Schizophrenia, follows logically from the treatment of the disorder with antipsychotic drugs such as chlorpromazine and fluphenazine. These drugs work by blocking dopamine D2 postsynaptic receptor sites, which inhibits the binding of dopamine, thus reducing positive symptoms (Seeman, 2011).