Has the Nature Vs Nurture debate finally been settled in regards to Schizophrenia? In 2016 mainstream national newspapers ran the story;
The original journal article (Sekar, 2016) the headline relates to proposed that ‘synaptic pruning’ occurs at pivotal points in development, however, excessive pruning during adolescence are matched to the symptoms experienced by Schizophrenics. The regulation of an individual’s synaptic pruning is specifically related to the gene ‘complement component 4‘ referred commonly to as ‘C4’.
It has long believed that Schizophrenia had an innate component, however, the difficulty in systematically testing the impact of the environment meant clear conclusions have always been difficult to draw. The Diathesis-Stress Theory suggest that Schizophrenia could be caused by a biological vulnerability (diathesis) triggered by environmental factors (stress).
Gottesman and Shields (1972) classic study attempted to pull research in the area together, by analysing a range of adoption and twin studies including dizygotic (non-identical) and the rarer monozygotic (identical) twins, which only occur 3 in every 1000 live deliveries worldwide. All adoption studies found an increased incidence of schizophrenia in adopted children with a schizophrenic biological parent. Kety (who was also known for his critique of Rosenhan’s study) found that biological siblings of children with schizophrenia showed a much higher percentage of schizophrenia. All twin studies found a higher concordance rate for schizophrenia in monozygotic (MZ) than dizygotic (DZ) twins. In Gottesman and Shield’s own study the rate was 58% for identical twins, and 12% for non-identical twins. The research was strongly suggestive of the genetic influence even back then, however, only took a reductionist biological view, largely ignoring the diathesis-stress model even though the results seem to support it.
Is the genie finally out of the bottle?
The current Sekar 2016 research is an exciting development in answering the questions of the biological cause of schizophrenia as well as how an effective treatment may be developed. Watch this space….