The risk for depression is increased in individuals with a tendency towards negative ruminations and depressive thought. It is known that patterns of autobiographical memory may also be predictive of depression.
In fact memory and concentration difficulties are common for those with a depressed mood. People with the disorder say that these cognitive problems are among the most disturbing symptoms.
But earlier studies were unable to verify this phenomenon in a clinical setting. Now a new study from the Center for BrainHealth at The University of Texas at Dallas has substantiated these memory deficits.
The findings could have repercussions for the way cognitive deficits are diagnosed and treated in depression.
Rumination and Negative Thought Loops
People with depressed mood showed up to a 12% reduction in memory compared to individuals without depressed mood when depressive thoughts are present. But they performed similarly to individuals without depressed mood when depressive thoughts are not present.
“Depression is an interference phenomenon. Rumination and negative thought-loops interfere with a person’s ability to think. We hypothesize that when individuals with depressed mood are exposed to stimuli, such as a meaningful song or a place that evokes sad feelings, the brain fixates on that and can’t focus on daily tasks such as a phone conversation or completing a grocery list,” explained Bart Rypma, Associate Professor in the School of Behavioral and Brain Sciences at The University of Texas at Dallas. “In a traditional laboratory setting, external cues that induce depressive thoughts and therefore interfere with cognitive performance are eliminated. In our study, we found a way to incorporate them and observe their effects on memory."
The study involved 157 undergraduate students who completed a computer-based depression inventory. The inventory measured self-reported, depressive symptoms experienced over the previous two-weeks.
Out of the 157, 60 participants were classified as having depressed mood and 97 as having non-depressed mood.
“The results suggest that individuals with and without depressed mood generally have a similar ability to actively remember information. However, when depressive thoughts are present, people with depressed mood are unable to remove their attention from this information, leading to deficits in their memory,” said lead author Nicholas Hubbard.
Depression and Working Memory
Researchers looked at working memory. Working memory is the cognitive function which enables the brain to store information for short periods of time so that other cognitive processes can happen simultaneously.
Study participants both with and without depressed mood were asked to respond ‘True’ or ‘False’ to a sentence featuring either depressive thoughts (e.g., “I am sad,” “People don’t like me”) or neutral information (e.g. “Most people agree that Monday is the worst day of the week”), and then remember a string of numbers at the end.
People with depressed mood forgot more numbers than people without depressed mood when they responded to the sentence featuring negative information. On the other hand they remembered just as many numbers when they responded to neutral information.
“Depression affects 151 million people worldwide and costs Americans $83 billion per year. Much of these costs are related to loss of productivity and increased rates of disability. Understanding and accurately diagnosing memory loss in depression is paramount for developing an effective therapeutic approach,” says Hubbard. “Our findings implicate that therapeutic approaches such as teaching one to recognize and inhibit depressive thoughts could be a key aspect to treating cognitive deficits in depression."
When asked to recall specific events, some individuals have a tendency to recall broader categories of events instead of specific events. This is termed over-general memory and, like those who tend to ruminate, these individuals also have a higher risk of developing depression.
How to Improve Memory
Cognitive training improves cognitive functioning, which can increase working memory capacity and improve cognitive skills and functions in those with working memory deficiencies. Cognitive training may focus on attention, speed of processing, neurofeedback, dual-tasking and perceptual training.
Cognitive training has been shown to improve cognitive abilities for up to five years.
In one experiment, the goal was to prove that cognitive training would increase the cognitive functions in older adults by using three types of training. The 3 types were memory, reasoning and speed of processing.
It was found that improvements in cognitive ability not only was maintained over time but had a positive transfer effect on everyday functioning.
These results indicate that each type of cognitive training can produce immediate and lasting improvements in each kind of cognitive ability, thus suggesting that training can be beneficial to improving memory.
Meditation, a form of mental training to focus attention, has been shown to increase the control over brain resource distribution, improving both attention and self-regulation. The changes are potentially long-lasting as meditation may have the ability to strengthen neuronal circuits as selective attentional processes improve.
Meditation may also enhance cognitive limited capacity, affecting the way in which stimuli are processed.
Studies have found that meditation decreases stress related cortisol secretion and may elevate brain-derived neurotrophic factor, which protects neurons against stress and stimulates the production of new neurons.
Meditation practice has also been associated with physical changes in brain structure. Magnetic resonance imaging of Buddhist insight meditation practitioners who practiced mindfulness meditation were found to have an increase in cortical thickness and hippocampus volume compared to the control group.
And research suggests that what food we eat can influence memory processing. Glucose, flavanoids, fat and calories all affect memory areas of the brain.
For More Information:
Nicholas A. Hubbard, Joanna L. Hutchison, Monroe Turner, Janelle Montroy, Ryan P. Bowles, Bart Rypma. Depressive thoughts limit working memory capacity in dysphoria. Cognition and Emotion, 2015; 1 DOI: 10.1080/02699931.2014.991694
Xueling Zhu, Xiang Wang, Jin Xiao, Jian Liao, Mingtian Zhong, Wei Wang, Shuqiao Yao. Evidence of a Dissociation Pattern in Resting-State Default Mode Network Connectivity in First-Episode, Treatment-Naive Major Depression Patients. Biological Psychiatry, 2012; 71 (7): 611 DOI: 10.1016/j.biopsych.2011.10.035
Willis, SL., Tennstedt, SL., Marsiske, M., Ball, K., Elias, J., Koepke, KM., Morris, JN., Rebok, GW., Unverzagt, FW., Stoddard, AM., & Wright, E. (2006). Long-term effects of cognitive training on everyday functional outcomes in older adults. National Institutes of Health, 296(23), 2805-2814.
Xiong, G.L. and Doraiswamy, M. (2009). “Does Meditation Enhance Cognition and Brain Plasticity?” Annals of the New York Academy of Sciences. Vol 1172, pages 63-69.