Genetic Influences on Mental Illness

There is more that contributes to the onset of mental illness besides the factors discussed in last month’s article concerning the brain and mental illness. In addition to looking at the biological origins of brain dysfunction, researchers are looking at another major component -genetics. It is hoped that these studies can lead to the prevention of mental illness and/or devising effective medication.

More than half of our genes are responsible for the development and functioning of our brains. Genes contain instructions that carry the code for the building blocks of our mind and body. Unhappily, things can go awry with this hugely complicated biological process-our forebears may be giving us DNA where critical genes are deleted altogether, or we get too many duplications of them, or some of the genes we get “miscode” proteins-all giving rise to genetic defects which will fundamentally compromise the developing brain.

Some research has identified a substantial overlap in genetic risk for schizophrenia and bipolar illness, caused by sub-microscopic mutations –a risk also shared in autism. A “hotspot” has been detected in a single stretch of genetic code, implicating immune system involvement in these disorders. The largest genetic analysis of this kind to date for bipolar disorder has found that a variation in only two genes causes the imbalance of sodium and calcium in brain cells which may be responsible for this illness.

Several studies of schizophrenia identified a wide range of small gene variations, which taken together accounted for 30% of the risk for schizophrenia. A mutation that deleted chunks of DNA increased the risk of schizophrenia eight-fold.

In another startling finding, the studies discovered that the rare occurrence of one extra copy of a gene can cause a sizeable risk for schizophrenia. These micro-deletions can be inherited, but they can also happen spontaneously, which is why some individuals can develop schizophrenia without having any family history of the illness. This could explain why – in spite of the fact that 80% of the risk of schizophrenia is familial - the incidence of schizophrenia remains at 1% of the population even though many people with this illness do not have children.

One of the hottest new areas in brain research is neurogenesis, a still-controversial hypothesis claiming that brain cells can heal, or regenerate. Physical and mental “workouts” are proposed to rejuvenate fatigued brain cells, and even create new ones, while preliminary animal research suggests that anti-depressants and lithium may actually spur development of new cells, and increase neuronal connections in the brain.

Because of research, medication and treatment for mental illness are constantly improving, but there is hope for even more and better.

Now is the time for the reminder: no one is to blame for mental illness any more than a person with mental illness or their family can be blamed for autism, Parkinson’s, epilepsy, diabetes, or other such illnesses.