Considered to be the largest genome-wide analysis of its kind, the study revealed that there is a high overlap between schizophrenia and bipolar disorder; moderate for bipolar disorder and depression as well as ADHD and depression, and low between schizophrenia and depression. If replicated, the data linking schizophrenia and depression could play a pivotal role in future research and diagnostics. Although researchers expect to see a greater overlap between ADHD and autism, the schizophrenia-autism connection is consistent with new and evolving data.
Naomi Wray Ph.D., of the University of Queensland, Brisbane, Australia, was one of the scientists that participate. “Since our study only looked at common gene variants,” Dr. Wray said, “the total genetic overlap between the disorders is likely higher… Shared variants with smaller effects, rare variants, mutations, duplications, deletions, and gene-environment interactions also contribute to these illnesses.
While the study attained valuable findings, most of the likely inherited genetic contributions to the conditions remain unexplained; especially the non-inherited genetic factors. Schizophrenia, for example, has an estimated total heritability of 81 percent, according to evidence from twin and family studies. Meanwhile common genetic variation accounted for 23 percent of the condition’s occurrences.
As the chief of the NIMH Genomics Research Branch, Thomas Lehner, Ph.D., stated: “It is encouraging that the estimates of genetic contributions to mental disorders trace those from more traditional family and twin studies. The study points to a future of active gene discovery for mental disorders.”