The connection between sleep and depression has been explored in several studies. When we sleep, the brain recharges in many ways. Short-term memories, such as events that happened during the day are either culled from the memory banks or converted into long-term memories and stored in the hippocampus.
The brain has to function correctly to do this, as well as to control emotions and negative feelings. Part of the problem many patients with depression report is getting "stuck" on a series of negative thoughts. This results in depressive thoughts and very often, poor sleep. In a 2008 study, over 75% of patients diagnosed with major depressive disorder reported significant trouble sleeping.
A collaboration of scientists from the University of Warwick in the UK and Fudan University in China found that in patients with depression there is a neural link between three specific areas of the brain. The connectivity issues between these areas are responsible for poor sleep quality, and it becomes a vicious cycle. Without proper rest, depression gets worse, but it's the depression and the neural linking of these areas that cause the poor sleep cycles.
The study analyzed data from roughly 10,000 people. Brain scans of patients with depression showed an abnormal amount of connectivity between the dorsolateral prefrontal cortex, which is where short-term memory is handled, the precuneus where thoughts of self are processed, and the lateral orbitofrontal cortex which is where negative thoughts often get "stuck." These underpinnings of the mechanism that occurs in depression were linked together by analyzing research studies.
Professor Jianfeng Feng, from the University of Warwick's Department of Computer Science, was a co-author on the study. He explained, "The understanding that we develop here is consistent with areas of the brain involved in short-term memory (the dorsolateral prefrontal cortex), the self (precuneus), and negative emotion (the lateral orbitofrontal cortex) being highly connected in depression, and that this results in increased ruminating thoughts which are at least part of the mechanism that impairs sleep quality."
Professor Edmund Rolls is a computational neuroscientist at Warwick and also worked on the study. He talked about the implications for this new knowledge, stating, "This study may also have implications for a deeper understanding of depression. This important cross-validation with participants from the USA provides support for the theory that the lateral orbitofrontal cortex is a key brain area that might be targeted in the search for treatments for depression."
Since sleep deprivation has been shown to have numerous adverse effects on productivity, mood, appetite, and emotional well-being, finding the connection in the brain between sleep and depression could lead to better treatments for patients with major depressive disorder. Poor sleep and depression impact more than one-third of the world's population said Rolls, so it could quickly become a severe public health issue. The study is published in the journal JAMA Psychiatry. Check out the video below to hear more about the work.