Major depression accounts for almost 4% of the disease burden in the United States. In 2015, about 16 million US adults over the age of 18 reported having had at least one major depressive episode in the previous year. Although there is a wide range of treatment options for depressed people, there is no cure and we still have a lot to learn. For this reason, research on brain activity associated with depression is essential. The precise causes of depression are not always clear, but some factors are known to play a role: poor sleep, for example, is a relatively common risk factor. Although insomnia and hypersomnia, or excessive somnolence, are both symptoms of depression, insomnia is more strongly associated with severity, onset and recurrence of depressive episodes. In fact, people without depression but with insomnia have twice the risk of developing depression compared to those who sleep well. Similarly, research has also shown that depressive symptoms improve in some individuals if sleep problems are alleviated. In recent years, researchers studying depression have increasingly focused on individual differences in brain function. In particular, a region called ventral striatum produced interesting results.
This is an area of the brain involved in reward, motivation and goal-directed behavior. Experiments have shown that reduced ventral striatal activity linked to reward is associated with depression. Furthermore, deep brain stimulation of the ventral striatum has been shown to have an antidepressant effect in people with treatment-resistant depression. It seems that high levels of ventral striatal activity related to reward can buffer the individual against the effects of negative experiences, reducing the likelihood of developing depressive symptoms. A study published in the Journal of Neuroscience looked at these theories in more detail, and examined whether the ventral striatum-related reward activity influenced the relationship between sleep disorder and depressive symptoms. The research was directed by Reut Avinun, PhD – from Duke University in North Carolina – who explained that this research follows two other studies in their laboratory, which show how the same brain region can modulate the effect of stress on depression. Studies have shown that people who suffered from stress and had high reward-related activation in the ventral striatum were less likely to report on depressive symptoms.
For their latest survey, they enrolled 1,129 young adults from the Duke Neurogenetics study. Firstly, the participants completed a questionnaire on the quality of their sleep. In total, 35% of the participants were characterized as “poor sleepers”. Subsequently, they played a game of guessing cards in which they received positive and negative feedback designed to trigger the ventral striatum. While playing, the researchers collected functional NMR data. They found that individuals with higher rewarded ventral striatal activity were significantly less likely to report symptoms of depression when they experienced poor sleep quality. This result remained significant even after controlling factors such as age, gender, race, early or recent stress and symptoms of anxiety. The results could be useful in the ongoing research of markers for the risk of depression. They also give an idea of how depression works.
Dr Avinun comments: “This same region has been associated with optimism, so it is possible that people with this high reward sensitivity can better cope with stressful and negative experiences by having a more positive outlook.The current findings are based on previous studies. , carving a significant role for the ventral striatum in the relationship between sleep and depression, but there is still a lot of work to do.In the future, I intend to better understand the susceptibility to depression, and identify individuals who are more at risk of developing depression by observing their brain and their DNA. Depression is still a condition that is difficult to predict and treat, but continued efforts along innovative pathways are generating meaningful insights into neuroscience and genetics below this pervasive condition”.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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