You spaced on that lunch meeting you said you’d attend, or you forgot a promise you’d made to a friend. Minor memory lapses strike us all from time to time. But if your brain seems increasingly unable to hold onto new information, stress may be to blame.
“There’s a lot of evidence to suggest chronic stress can lead to memory impairments,” says Jason Radley, an assistant professor of brain sciences at the University of Iowa. Radley's research has shown high or prolonged spikes in the stress hormone cortisol may “prune” the synapses in your brain’s prefrontal cortex and hippocampus, which are essential for certain brain functions, including memory.
“Stress levels naturally elevate through the process of aging,” Radley says. “And for those who suffer from chronic stress, it seems the cumulative exposure to cortisol over a person’s lifespan may produce a weathering of the brain and an erosion of cognitive functioning.”
It’s less clear if a super-stressful week or month could make a young person more forgetful, Radley says. Instead, your stress may be messing with your sleep.
“Sleep loss can disrupt the process of memory consolidation,” or sorting and storage, says Christoph Nissen, a professor of sleep medicine at the University of Freiburg in Germany. His research suggests sleep provides your brain the opportunity to both replay and strengthen new memories while also discarding the frivolous stuff you don’t need to remember.
Sleep loss can also hurt your brain’s ability to encode new memories, Nissen says. So in more ways than one, a poor night’s sleep can hamper your memory. Your goal should be eight hours every night, though an occasional night of just six hours of sleep won’t do much damage to your memories, Nissen says.
Stress and sleep aside, multitasking behaviors can also disrupt your brain’s ability to store new memories, says David Meyer, a professor of psychology and cognition at the University of Michigan who has studied the impacts of multitasking on memory. “When you’re multitasking, that’s interfering with processes that normally would be devoted 100% to doing the mental work that moves info from short term memory into long term memory,” he explains.
He mentions a well-known experiment during which researchers observed the brain activity of people who were trying to learn new information while multitasking. Compared to a group that was focused solely on learning the new info, the multitaskers had disruptions in the parts of their brain used for learning and memory consolidation. On a follow-up test, the multitaskers had higher error rates than their single-focus counterparts, Meyer says.
Your brain needs small breaks after a task in order to lock away new memories. If you’re replying to emails while participating in a conference call or chatting with a colleague, Meyer says, your over-tasked mind just won’t have the chance to store the new information it’s collecting.