9th FENS Forum of Neuroscience
Scientists from the Max Planck Institute of Psychiatry in Munich speak about the correlation of sleep problems with stress-related disorders and the influence of adversities during childhood on stress susceptibility in later life
Could sleep problems predict depression?
Troubled sleep is a well-known hallmark of depression. Most patients of stress-related disorders, including mood disorders, additionally suffer from sleep disorder. Sleep disturbance in depression is linked to increased levels of a stage called REM sleep leading to less deep sleep and early awakenings. Impaired sleep is also linked to increased production of CRH, a stress hormone.
Mayumi Kimura from the Max Planck Institute of Psychiatry in Munich asked whether causes of mood disorders are equivalent to those of sleep disorders. Her team examined how changes in REM sleep might be linked to stress and anxiety factors. They observed, measured and analyzed sleep and behavioral patterns in specially-generated mice. Some mice overproduced the stress hormone CRH in limited brain areas, other mice exhibited high anxiety-related behavior. The scientists examined which type of animal model would exhibit hallmarks of sleep disorders and might be suitable to further understand molecular mechanisms of sleep and mood disorders.
The research in mice so far has demonstrated that altered REM sleep is very much connected to mood disorders. The findings also clarified that CRH and anxiety — already linked separately to depression and to sleep disturbance — directly influence REM sleep patterns.
"So how does it all connect and how does it relate to humans?" asked Mayumi Kimura. “People with chronically impaired sleep might be more predisposed to depression.” If changes in sleep habits occur before patients have depression symptoms, knowing more about these associations might eventually improve prediction. These results could therefore be important for ongoing research on REM sleep in humans, enabling enhanced assessment of vulnerability or therapy outcomes.
Can childhood stress make you stronger?
Experiencing adversity in childhood can generate long-lasting brain changes affecting learning and memory or leading to various disorders. "Until now, human studies have indicated that early life stress generally correlates with increased risk for psychiatric disorders such as depression," noted Mathias Schmidt from the Max Planck Institute of Psychiatry in Munich. “But not everyone who experiences early adversity develops a mood disorder. Some individuals are more stress-resilient than others.” Thus, additional factors may need to be taken into account, including genetic risk and adult living or work environments in relation to early life conditions.
Behavioral screening and molecular examination indicated that mice with certain genetic factors adapted better to adult stress. Moderate adversity during development resulted in increased stress resilience in adulthood. But those mice less genetically prone to adaptation were more affected by adversity.
"Taken together, our data call for a balanced view on the consequences of early life adversity," said Mathias Schmidt. “Genetically predisposed individuals facing early stress might have an increased risk for later psychiatric disorders”, he explained. “But others genetically predisposed to be less affected might be better equipped to deal with similar challenges in adulthood.” Thus, a rough childhood may or may not make a person more resilient to stress in adult life. "There is no magic bullet to take away early life stress," said Mathias Schmidt. "But, at least in mice, we are beginning to know how this works in the brain.