Final answer:
The findings suggest that genetic heterogeneity exists in bipolar disorder, meaning that multiple genes or genetic factors can be involved in causing or contributing to the disorder.
Step-by-step explanation:
The findings that each extended family had its own mutations in the search for gene variants that cause or contribute to bipolar disorder in the 1980s indicate that genetic heterogeneity exists in bipolar disorder. This means that multiple genes or genetic factors can be involved in causing or contributing to the disorder. It suggests that bipolar disorder is not caused by a single gene or mutation. In the 1980s, when researchers began seeking gene variants that caused or contributed to bipolar disorder, it appeared that each extended family had its own unique mutations. These observations suggest that there is a high level of genetic heterogeneity in bipolar disorder, meaning that multiple genetic variants are likely contributing to the condition rather than a single gene mutation. The findings do not support the ideas that bipolar disorder is caused by a single gene, that environmental factors are negligible, or that mutations are unrelated to the disorder.
This understanding of genetic heterogeneity in bipolar disorder highlights the complexity of the disorder and the need for further research to identify and understand the specific genes and genetic factors involved. It also suggests that environmental factors may interact with these genetic factors to influence the development and manifestation of bipolar disorder.