Without evolution, the brain would not have the size, capability or connectivity that offer humans such advantages. But the same genetic changes that created bigger, better brains likely produced the potential for neural disorders like schizophrenia as part of the process, according to an August 2018 study published in the American Journal of Human Genetics.
The study points to the CACNA1C gene, part of the gene family that makes up calcium channels that support cell functions in many important ways.
Researchers noted an expanded DNA sequence in the CACNA1C gene helped create a highly advantageous brain function for humans.
But their findings indicate the same genetic markers may have also made certain neural disorders possible, particularly schizophrenia and bipolar disorder. Both of these neuropsychiatric diseases only occur in humans.
In simple terms, scientists have strongly and repeatedly linked susceptibility to schizophrenia to a 100 kb interval in the third intron CACNA1C gene.
Schizophrenia: A Modern Name For An Ancient Ailment
Though Emil Kraepelin first identified schizophrenia as a distinct mental illness in 1887, symptoms of the ailment have been documented since antiquity. Like other neural disorders, schizophrenia was once considered evidence of a person being possessed by demons.
Ancient artifacts have been uncovered with small holes drilled in the skull and documentation from those civilizations indicated that the process was intended to let evil spirits out.
From old movies and common cultural descriptions, many people still think of schizophrenia as a “split personality.” But that’s not accurate. Instead, the disorder is most accurately defined as serious mental illness that keeps sufferers from thinking clearly, managing their emotions or relating to other people.
Complex and long-term, schizophrenia affects about one percent of Americans. Characteristics include hallucinations that may involve a person with schizophrenia hearing voices or seeing things others don’t, delusions and disorganized thinking.
One of the most serious repercussions of schizophrenia is that sufferers ordinarily do not know they have it.
The Genetic Link
Genetics is the leading cause of schizophrenia, which adds weight to the possibility of its being an evolutionary side effect from the workings of the CACNA1C gene.
It occurs in one percent of the general population, but the rate soars to 10 percent for people who have a biological parent or sibling with the disorder.
The risk may be increased by drug use during a person’s teens or early 20s. Earlier onset of drug use increases the potential risk.
An environmental factor that may increase the risk in fetuses is exposure to viruses or malnourishment during the first and second trimesters. Another non-genetic risk factor is problems with brain chemicals like the neurotransmitters called dopamine and glutamate also might add to the risk.
Future Treatment Strides
Now that researchers have learned certain aspects of brain evolution also allowed mental illness like schizophrenia and bipolar disorder to develop along the same paths, scientists will continue to refine and expand on the findings.
Ideally, though, medical professionals will eventually be able to use the findings and associated discoveries to help diagnose schizophrenia and design appropriate genotype-targeted treatment for its sufferers.