Scientists believe schizophrenia and bipolar disorder could be part of the same mental illness as they share the same genetic causes.
Researchers from the Karolinska Institute in Stockholm, Germany, think that understanding the links between the conditions could help improve treatments and the development of drug therapies.
Bipolar disorder, known in previous years as manic depression, is recognised by extreme mood swings from low depression to excitable mania. Schizophrenia is a psychotic illness that can result in delusions and hallucinations.
The study published in the Lancet medical journal found that the family risk of inheriting a susceptibility to either of the disorders was similar.
Siblings were nine times more likely than a non relation to have schizophrenia and eight times more likely to have bipolar disorder, the research of more than nine million people suggests.
Authors Dr Paul Lichtenstein and Dr Christina Hultman wrote: “We showed evidence that schizophrenia and bipolar disorder partly share a common genetic cause. These results challenge the current dichotomy between schizophrenia and bipolar disorder, and are consistent with a reappraisal of these disorders as distinct diagnostic entities.”
Copyright Press Association 2009