Sleep disturbance is a significant risk factor for depression.
Major depression is responsible for almost 4 percent of the disease burden in the United States. In 2015, around 16 million U.S. adults aged 18 or older reported having had at least one major depressive episode in the previous year.
Although there is a range of treatment options for people with depression, there is no cure and we still have much to learn. Because of this, research into the brain activity associated with depression is paramount.
The precise causes of depression are not always clear, but certain factors are known to play a part: poor sleep, for instance, is a relatively common risk factor.
Sleep disturbance and depression
Although insomnia and hypersomnia, or excessive sleepines, are both symptoms of depression, insomnia is more strongly associated with the severity, onset, and recurrence of depressive episodes.
In fact, people without depression but with insomnia have twice the risk of developing depression when compared with those who sleep well. Along similar lines, research has also shown that in certain individuals, depressive symptoms improve if sleep issues are relieved.
Over recent years, researchers studying depression have focused more and more attention on individual differences in brain function.
In particular, a region called the ventral striatum has yielded interesting findings. This is an area of the brain involved in reward, motivation, and goal-directed behavior.
Experiments have demonstrated that reduced reward-related ventral striatum activity is associated with depression. Also, 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 reward-related ventral striatum activity may buffer the individual against the effects of negative experiences, reducing the likelihood of developing depressive symptoms.
Ventral striatum and depression investigated
A study published this week in the Journal of Neuroscience took a look at these theories in more depth and examined whether or not reward-related activity in the ventral striatum influenced the relationship between sleep disturbance and depressive symptoms.
The research was headed up by Reut Avinun, Ph.D. - from Duke University in North Carolina - who recently spoke with Medical News Today. She explained that this research follows on from two other studies at their laboratory demonstrating how the same brain region could modulate the effect of stress on depression.
"[The studies] showed that individuals who experienced stress and had high reward-related activation in the ventral striatum were less likely to report on depressive symptoms."
For their latest investigation, they enrolled 1,129 young adults drawn from the Duke Neurogenetics Study. Firstly, the participants completed a questionnaire about the quality of their sleep. In total, 35 percent of participants were characterized as "poor sleepers."
Next, they played a card-guessing game wherein they received positive and negative feedback designed to trigger the ventral striatum. As they played, the researchers collected functional MRI data.
They found that individuals with higher reward-related ventral striatum activity were significantly less likely to report symptoms of depression when experiencing poor sleep quality. This result remained significant even after controlling for factors such as age, sex, race, early or recent life stress, and symptoms of anxiety.
Dr. Avinun summarized the findings for MNT.
"In our study, we showed how the negative effects of poor sleep can also be modulated by [the ventral striatum], so that high reward-related activation can buffer the effect of poor sleep on depressive symptoms."
The results may be useful in the ongoing hunt for biomarkers for depression risk. They also give an insight into how depression works.
Speaking with MNT, Dr. Avinun explained, "This same region has been associated with optimism, so it's possible that individuals with this high reward responsiveness can cope with stressful and negative experiences better by having a more positive outlook."
The current findings build on earlier studies, carving a significant role for the ventral striatum in the relationship between sleep and depression. Of course, there is plenty more work to be done.
As Dr. Avinun told us, "In the future, I plan to work on gaining a better understanding of depression susceptibility; and help to identify the individuals who are more at risk of developing depression by looking at their brain and DNA."
Depression is still a difficult condition to predict and treat. However, continued efforts along innovative paths are generating significant insights into the neuroscience and genetics beneath this pervasive condition.