Why is it helpful to identify genes that influence susceptibility to Bipolar Disorder?
People usually think that for researchers finding genes that are involved in susceptibility to bipolar affective disorder is an end in itself. This is quite wrong. Finding genes is simply the first step on the path to better understanding of the brain processes that are involved in illness. To date, we have a very poor understanding of the causes of bipolar disorder; as a result, treatments are not effective in all patients and often cause troublesome adverse effects. Being able to pinpoint the mechanisms involved in causing an individual’s illness would provide the possibility of much more effective diagnosis and tailoring of treatments to the individual.
Modern molecular genetics provides extremely useful methods to discover the biological processes that are important in illness. Thus, it is best to view molecular genetics as a powerful tool to help understand more about the biological, psychological and social processes involved in illness. Improved understanding is crucial to developing improvements in diagnosis and treatment.
Is the aim to change people’s genes?
Absolutely not. There is a complex interplay between multiple genetic and environmental factors in influencing an individual’s susceptibility to mental illness. Many of the very same gene variants that in some people predispose to illness almost certainly confer positive attributes in the same people as well as those unaffected by illness. Thus, quite apart from social and ethical considerations it is not desirable to alter such genes.
Can genetics be used to help understand environmental risk factors?
Yes. Some individuals at very high genetic risk (e.g. The identical co-twin of an individual with illness) do not develop illness. Presumably such individuals have been exposed to powerful protective factors or have not been exposed to an important environmental risk factor. Some individuals at low genetic risk (e.g. No family history of similar disorder) develop illness.
Presumably such individuals have been exposed to powerful environmental risk factors. Thus, studying individuals at high and low genetic risk can be very useful for identifying important environmental risk and protective factors.
Why does the study need so many participants?
Rather than there being one single gene influencing susceptibility to bipolar disorder, we know that several, or many, genes are involved in influencing susceptibility to the illness. Each susceptibility gene plays a relatively small role in influencing disease risk and in most cases it is not correct to think in terms of the variants being “abnormal”. It is the collection of susceptibility gene variants that an individual inherits, together with their environmental experiences that determines whether they become ill. In other words, several genes interact together with environmental factors to influence susceptibility to illness.
It is now known that large numbers of individuals (thousands) are required for genetic studies of bipolar disorder in order to identify these genes that play a relatively small role in influencing risk of illness.