Traditionally, depression is suspected when symptoms that suggest impaired psychosocial functioning are present for more than two weeks. Symptoms of depression include an overwhelming feeling of sadness, difficulty to experience pleasure, sleep problems, and difficulties with engaging in everyday life.
This clinical presentation of depression guides physicians to make a diagnosis and to select antidepressant treatment such as drugs or psychotherapy.
Currently, at least 40 percent of depressed patients actually benefit from antidepressant treatment, whereas 20 to 30 percent of patients may suffer from chronic depression that negatively impacts their quality of life.
Emerging research addresses the neural bases of depression as well as how treatment can induce changes in the brain. Modern brain imaging techniques such as functional magnetic resonance imaging (fMRI) are often used to view brain modulations.
This line of research expands the commonly accepted premise that depression is associated with dysfunction of specific brain regions involved in cognitive control and emotional response.
In order to improve the efficiency of treatment and reduce the burden of depressive disorders, depression clearly needs to be defined at the neurobiological level.
A recent fMRI study showed that depressed patients had an abnormal activation of the medial prefrontal cortex. During this study, subjects had to judge whether personality traits described them or not (i.e. ‘Am I selfish?’), or whether it described a generally desirable trait or not (i.e. ‘Is it good or bad to be greedy?’).
The dysfunction of the medial prefrontal region may explain specific complaints of depressed patients such as self-blame, rumination and feeling of guilt.
It was observed that this activation pattern was maintained over the course of depression after 8 weeks of antidepressant treatment. These results are difficult to interpret but suggest that, after remission of depression, some patients show persistent abnormalities of specific brain regions.
Such abnormalities may indicate the need for complementary treatment such as cognitive behavioral therapy in order to reduce the risk of depressive recurrence.
Overall, these findings contribute to the argument that brain imaging studies could provide biomarkers of diagnosis and improve patients’ chances to responding to specific treatment modalities. Such neurobiological markers of depression may help psychiatrists to tailor antidepressant treatment to the brain and the biological needs of the patients. However, despite over a decade of such research, no such biomarkers have been found.
In the general population, depression is still frequently associated with or perceived as a bad lifestyle, impairment of judgment, bad choices, and ‘psychological weakness.’
However, the results of brain imaging studies demonstrate that depression impacts the brain, and is associated with dysfunction of specific brain regions involved in cognitive control and emotional response.