A sleep abnormality likely plays an important role in schizophrenia, according to sleep experts at Beth Israel Deaconess Medical Center (BIDMC). In a review of the growing body of evidence linking a reduction in sleep spindle activity to schizophrenia, the researchers suggested that a better understanding of this sleep abnormality’s genetic underpinnings opens the door to new treatments for the psychiatric disorder. Their paper appeared in the October 15 issue of Biological Psychiatry.“One of the most exciting advances in sleep research over the last decade has been the growing understanding of sleep’s causal relationship to psychiatric disorders,” said senior author Robert Stickgold, MD, PhD, director of the Center for Sleep and Cognition at BIDMC. “Here, we reviewed the evidence that reduced sleep spindle activity predates the onset of schizophrenia and contributes to its cognitive deficits and other symptoms.”
Visible on an electroencephalogram (EEG) – which measures the brain’s electrical activity – sleep spindles are bursts of brain activity lasting less than a second. They occur only during the non-REM phase of sleep and play a role in the memory consolidation process that takes place during sleep. Scientists suspect sleep spindles solidify memories by strengthening synaptic connections among neurons. Among both healthy subjects and individuals with schizophrenia higher sleep spindle activity correlates with enhanced sleep-dependent memory processing and higher IQ.For nearly a century, researchers have been aware of the link between sleep disturbances and schizophrenia but these disturbances have long been considered a secondary consequence of the illness. Now, a growing body of literature suggests sleep abnormalities actually contribute to the onset, relapse and manifestations of schizophrenia – not the other way around.
A chronic and severe mental disorder, schizophrenia is marked by psychotic symptoms including hallucinations, delusions and thought disorders. But, the scientists wrote, for many people with schizophrenia, it’s the chronic cognitive deficits – impaired memory, inability to focus and poor executive functioning – that can be most debilitating, keeping up to 80 percent of people with the disorder out of the workforce even when their psychotic symptoms are well-controlled.Stickgold and colleagues, including first author Dara Manoach, PhD, a neuropsychologist at Massachusetts General Hospital and an associate professor of psychology at Harvard Medical School (HMS), reviewed a spate of studies, which – while small – link reduced spindle activity with the cognitive symptoms common to schizophrenia, including poor motor procedural memory and learning, worse executive function and lower IQ