Genetics and Mental Illness Overview

Researchers are uncovering more and more about how the brain is affected by mental health conditions, yet we still can’t definitively pinpoint their underlying causes. If we’re going to prevent mental health conditions from developing, or create medications that do more than just reduce symptoms, we have to be able to identify and understand the biological basis of brain dysfunction.

Researchers are searching the human genome for genes associated with each disease. One researcher said, “Mental health care in the future will be revolutionized by genetics, which will change the way medicine is practiced from a diagnostic standpoint and a treatment standpoint.” In the center of each of our cells is the DNA we inherit from our parents—our human genome contains more than three billion DNA units. Our DNA “programs” our genes, which are segments of DNA that shape how our body is made, how we act and how our brains develop and function.

Genes also guide how our brain cells are made: the connections between them, the networks they create as the brain develops, the chemical messengers that allow brain cells to communicate with each other. 
Unfortunately, things can go wrong with this complicated process. One of the things that can go wrong is basic heredity. We may inherit from our ancestors DNA where critical genes were copied, deleted or programmed incorrectly. These changes can cause genetic defects that can fundamentally change how a brain develops. Researchers have also found that changes can occur in genes for a variety of reasons other than heredity. “Genomics research” in mental health focuses on how genes, and the changes they undergo, influence the development of brain circuitry, brain functions and what may cause brain disorders. 

Recent Findings

We now know that certain gene variations are involved when chemical messages between cells get interrupted. Neurotransmitters are responsible for delivering these chemical messages. Neurotransmitters continue to be studied to better understand what goes on in mental health conditions. For example, researchers noticed that psychosis is linked to too much dopamine in the brain—the belief that one neurotransmitter, dopamine, is responsible for psychosis is the influential “dopamine hypothesis.” Anti-psychotic medications are based on this hypothesis. However, new research suggests a different part of the process may also be key; problems in the glutamate messenger system that produces too much dopamine is a newer area of research. People are now developing medications that target the glutamate system and the neuro-regulators involved in it—GABA and NMDA.

Researchers have found that there’s a large overlap for genetic risk between schizophrenia and bipolar disorder; the risk is caused by sub-microscopic mutations called “single nucleotide polymorphisms.” These are SNPs, or “snips.” The autism spectrum disorders share the risk of these same mutations. One stretch of genetic code involved in these conditions suggests that the immune system may be involved. The largest analysis of genetics in this area shows that a variation on two genes causes an imbalance of sodium and calcium in the brain and may cause bipolar disorder.

Studies on schizophrenia have found several genetic patterns associated with the condition. A variety of small variations in genes—or copy number variants (CNVs)—account for 30 percent of the risk for schizophrenia. A mutation that deletes certain sections of DNA increased risk of schizophrenia. One extra copy of a certain gene (a rare event) adds a significant amount of risk for schizophrenia. These small variations can be inherited but can also happen spontaneously, which may account for one of the reasons some people develop schizophrenia without having any family history of the condition. 

A recent and controversial area of genomic brain research is neurogenesis. Neurogenesis hypothesizes that brain cells can heal through physical and mental workouts, potentially “healing” damaged cells and creating new ones. Early animal research suggests that anti-depressants and lithium may cause new brain cells development and increase the connection between cells. 

Although none of this genomic research has led to a simple test, such as a blood test, to diagnose mental health conditions, we continue to hope that further research will better enable people to find the best treatment for them.