Final answer:
Researchers cannot establish causation solely from a correlation between poor family communication patterns and schizophrenia; both genetic vulnerability and environmental factors play roles in the development of this complex disorder.
Step-by-step explanation:
Even if a strong correlation is found between poor communication patterns in families and the presence of a schizophrenic child, researchers cannot tell whether poor communication is a cause or effect of schizophrenia. This question touches upon the complexity of gene-environment interactions in the development of psychiatric conditions like schizophrenia. The study by Tienari and colleagues found that adoptees with a high genetic risk who were raised in disturbed home environments had a significantly higher likelihood (36.8%) of developing schizophrenia compared to those with a high genetic risk in healthy family environments (5.8%). This supports the idea that both genetic vulnerability and environmental stress contribute to the development of the disorder. Nonetheless, the directional causality between family communication patterns and schizophrenia cannot be firmly established through correlation alone.