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Depression is a severe form of psychiatric illness that can produce debilitating life changes if not properly addressed. Unfortunately, according to the results of an extensive study review conducted by the National Institute of Mental Health, only roughly 33 percent of all people with depression respond well to the first medications used to treat their symptoms. In addition, another 33 percent of depression sufferers continue to respond poorly despite the use of multiple antidepressant medications. A new study published in 2013 in the journal Biological Psychiatry indicates that genetic differences between depression patients account for much of the varied response to antidepressants.

Antidepressant Basics

Doctors commonly prescribe antidepressants to address the symptoms of both moderate and severe forms of depression. There are a number of different types or classes of antidepressant medications, which doctors, regulators and pharmaceutical manufacturers group together according to their specific chemical effects on the body and brain. Examples of these medication classes include SSRIs (selective serotonin reuptake inhibitors), SSNRIs (selective serotonin and norepinephrine reuptake inhibitors), tricyclic antidepressants, tetracyclic antidepressants, atypical antidepressants and MAOIs (monoamine oxidase inhibitors). Broadly speaking, the most frequently prescribed classes of antidepressants are SSRIs, SSNRIs and atypical antidepressants, which produce relatively minor side effects in most people. Tricyclic and tetracyclic antidepressants generally trigger more side effects, and therefore doctors prescribe them less often. MAOIs produce powerful treatment benefits, but they also produce powerful side effects that limit their safety and usefulness in most situations.

No one knows for sure who will respond well to what types antidepressant medications, the Mayo Clinic explains. Typically, doctors start their patients on the safest, most widely effective options, and then try other medications if and when the need arises. In some cases, doctors can produce the greatest treatment benefits by prescribing specific combinations of multiple antidepressants. As is true with single prescriptions, the goal is to effectively reduce a depression patient’s most serious symptoms while simultaneously protecting him or her from the worst harms associated with antidepressant side effects. In some cases, doctors also treat depression with medications other than antidepressants, including such options as antipsychotics (also known as neuroleptics), mood stabilizers, stimulants or anti-anxiety medications (also known as anxiolytics).

Genetic Response Basics

In the 2000s, doctors and medical researchers have much more knowledge about the details of human genetics than professionals working in any previous generation. Gradually, they have started using that knowledge to identify specific details in our genetic makeup that predispose us to respond in certain ways to various environmental influences, including the influences of diseases and disease treatments. Experts in the field generally refer to these details as “biomarkers.” Essentially, these markers are features or abnormalities in a person’s DNA that have an effect on how that person reacts to internal or external circumstances. Some individual features and abnormalities are strong enough to prominently influence a person’s responses on their own. Many others only exert a strong effect in combination with a range of other features or abnormalities.

Genetic Responses to Antidepressants

In the study published in Biological Psychiatry, a team of researchers from Great Britain’s King’s College used an advanced form of genetic analysis to gauge the medication responses of 2,800 people taking antidepressants to treat the symptoms of major depression. These researchers concluded that individualized genetic response accounts for roughly 42 percent of the total population-wide effectiveness of antidepressant medications. In practical terms, this means that currently there’s no real way to determine what type of result that antidepressants will produce in close to half of all depression patients. It also means that, without detailed genetic information, no doctor can tell a given patient in advance how he or she will react to antidepressant treatment.

In addition to drawing a broad conclusion about the influence of genetics on the response to antidepressants, the authors of the King’s College study also concluded that none of the individual genetic biomarkers for antidepressants exerts a particularly strong influence on the body’s overall antidepressant response. Instead, an undetermined number of biomarkers combine to produce any given individual’s response to these medications. This second finding has two major consequences. First, it means that future researchers must take the time and effort to uncover a potentially extensive range of biomarkers before they can fully determine exactly how genetic factors and antidepressants interact. It also means that it will be quite some time before pharmaceutical researchers can start developing medication options that take the varied genetic responses to antidepressant treatment into account.

 

 

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