Nature or Nurture as a complex interplay: the debate over the depression gene

by admin · 11th August 2009

By Dena T. Smith

In the last several decades, the field of medicine has become increasingly dominated by biological thinking. Psychiatry, a sub-field aimed at treating mental illness is largely focused on the genetic causes of a wide range of conditions. This perspective stands in opposition to the notion that environmental factors cause symptoms – that changes in biology and/or neurochemistry are dictated by certain situations and conditions to which an organism is exposed. Depression is one illness category under scrutiny as of late. The majority of psychiatric studies on depression claim a genetic responsibility for this condition. Some even conclude that there is a single serotonin gene responsible for this disease, making it seem as though the gene-environment puzzle has been solved; differences in one gene or several explain why people respond differently even to the same conditions.

There has been fervent disagreement from mental health researchers outside psychiatry, but, in the last few months there has been opposition to the one-gene argument from within the psychiatric world. A review in the June 17th edition of JAMA attempts to replicate the 2003, ‘single-gene’ findings of Caspi et al and show that the relationship between genes and environment is far more complicated and muddled than one serotonin gene causing an illness. In fact, these researchers found more evidence that stressful life events would predict depressive episodes than would a particular gene. While this is a complicated debate and there is certainly no clear answer, discussions such as this highlight the importance of the work of sociologists of mental health. Epidemiological studies show, time and again, that factors such as poverty, gender, ethnicity, and culture more broadly affect one’s likelihood to become depressed – or to experience a range of what psychiatry views as pathological, neuro-biologically driven conditions.

In the currently dominant psychiatric paradigm, pathology (difference from the norm) indicates a flaw in the genetic make-up of the individual. From a sociological perspective, pathology is likely to be located in situational factors – the social structure and culture. Additionally, the stress paradigm, the most dominant perspective in the sociology of mental health and illness provides evidence that certain environmental factors either increase or decrease the likelihood of experiencing stress. For example, having coping mechanisms for dealing with events and situations or having a support system when faced with stress or trauma would decrease the odds of a negative outcome such as increased stress, which can lead to depressive symptoms. On the other end of the spectrum, not having these protective factors can likely lead to increased stress and a greater likelihood to experience unfortunate symptoms. There is a wide body of evidence that these environmental, structural and cultural factors are directly linked to changes in stress levels.

There are several different issues that arise from the predominance of biological explanations in psychiatry. One is that, due to psychiatry’s prominent role in society, we tend to ignore the other factors that are clearly linked to negative psychological consequences for individuals – the environmental or social antecedents to suffering. Another is that we are increasingly pushed towards treatments that are biologically-based rather than socially or culturally driven. For instance, treating an individual with an antidepressant may reduce symptoms of unhappiness (and this is not insignificant and may be quite necessary and successful in some cases), but does not in fact alleviate the root cause of the problem if, say, said individual’s sadness is caused by economic stress (see the link below), stressful work environment, lack of a support system, etc.

Ultimately, challenges to the one-gene, many-gene or even neurobiology-only studies are an important addition to the discussion within psychiatry – one that has existed outside the medical field for quite some time. This is but one example that begs the question of whether any psychiatric conditions (or even physical illnesses) are caused only by the cogs within the machine of the body. None of us exist in a vacuum, of course, and while environmental explanations alone may not be sufficient, continued probing at the environment-biology link in order to understand the complex interplay between the two is a necessary and potentially fruitful area of investigation.