Genetic Link Between Psychiatric Disorders
Genetic Link Between Psychiatric Disorders
Psychiatric disorders, which are relatively common and associated with considerable distress and functional impairment, have strong evidence of being complex and partly genetic in origin. Scientists have long recognized that many psychiatric disorders tend to run in families, suggesting potential genetic roots.
Major mental disorders traditionally thought to be distinct share certain genetic glitches, according to a new study. This finding may point to better ways to diagnose and treat these conditions. Such disorders include autism, attention deficit hyperactivity disorder (ADHD), bipolar disorder, major depression, and schizophrenia. Symptoms can overlap, and so distinguishing among these five major psychiatric syndromes can be difficult. Their shared symptoms suggest they may also share similarities at the biological level.
Recent studies have turned up limited evidence of shared genetic risk factors, such as for schizophrenia and bipolar disorder, autism and schizophrenia, and depression and bipolar disorder. To take a broader look, an international research consortium conducted an analysis that incorporated data from genome-wide association studies (GWAS) of the five major disorders. This type of study involves scanning through thousands of genetic markers in search of tiny variations that appear more often in people who have a particular condition than in those who don’t.
The scientists screened for evidence of illness-associated genetic variation among over 33,000 patients. All had been diagnosed with at least one of the five disorders. A comparison group included about 28,000 people who had no major psychiatric diagnosis. The analysis revealed variations significantly associated with all five disorders. These included variations in two genes that code for the cellular machinery that helps regulate the flow of calcium into neurons.
Variation in one of these, called CACNA1C, had previously been linked to bipolar disorder, schizophrenia, and major depression. CACNA1C is known to affect brain circuitry involved in emotion, thinking, attention, and memory functions that can be disrupted in mental illnesses. Variation in another calcium channel gene, called CACNB2, was also linked to the five disorders.
In addition, the researchers discovered illness-linked variation for all five disorders in certain regions of chromosomes 3 and 10. Each of these sites spans several genes, and causal factors havent yet been pinpointed. The suspect region along chromosome 3 had the strongest links to the disorders. This region also harbors certain variations previously linked to bipolar disorder and schizophrenia.
Although statistically significant, each of these genetic associations individually can account for only a small amount of risk for mental illness, says study co-author Dr. Jordan Smoller of Massachusetts General Hospital.
In conclusion, while genetic influences play a significant role in risk for psychiatric disorders, it’s important to note that mental illness is most probably caused by a combination of genetic and environmental components. Furthermore, genetic tests cannot accurately predict your risk of developing a mental disorder. Although research is underway, scientists dont yet know all the gene variations that contribute to mental disorders, and those that are known, so far, raise the risk by very small amounts.