Depression is linked to memory decline, study finds

Depressive symptoms are linked to subsequent memory decline in older people, a new study has found.

The study, carried out by researchers at University College London (UCL) and Brighton and Sussex Medical School, also found that poorer memory is linked to an increase in depressive symptoms later on.

Researchers looked at 16 years of longitudinal data from 8,268 adults in England with an average age of 64. The data was from the English Longitudinal Study of Ageing (ELSA), in which a nationally representative population sample in England answers a wide range of questions every two years.

The research, published in Jama Network Open, found that depression seemed to affect memory, and vice versa. The study team accounted for a range of factors that might have affected the results, such as physical activity and life-limiting illness. Because the study was observational, it could not establish causality.

Dr Dorina Cadar, senior author on the study and a senior lecturer at Brighton and Sussex Medical School, said: “It is known that depression and poor memory often occur together in older people, but what comes first has been unclear.

“Our study shows that the relationship between depression and poor memory cuts both ways, with depressive symptoms preceding memory decline and memory decline linked to subsequent depressive symptoms.

“It also suggests that interventions to reduce depressive symptoms may help to slow down memory decline.”

Important to monitor memory changes in older people

Lead author Jiamin Yin, a UCL graduate who is now a doctoral student at the University of Rochester, New York, said: “These findings underscore the importance of monitoring memory changes in older adults with increasing depressive symptoms to identify memory loss early and prevent further worsening of depressive function.

“Conversely, it is also critical to address depressive symptoms among those with memory decline to protect them from developing depression and memory dysfunction.”

While the reasons for the association are not completely clear, the researchers suggested that changes in the brain caused by depression might cause memory loss. These include lower levels of serotonin and dopamine, structural changes in regions involved in memory processing, and disruptions to the brain’s ability to re-organise and form new connections.

The researchers also said that psychological factors such as rumination – repetitive thinking or dwelling on negative feelings – might lead to memory impairment.

Similarly, people who have memory lapses can experience frustration, loss of confidence and feelings of incompetence, which could trigger depressive episodes.

Memory impairment may also disrupt daily functioning and social interactions, which may lead to people becoming isolated, also potentially triggering depressive symptoms.

Dr Cadar added: “Depression can cause changes in brain structures, such as the hippocampus, which is critical for memory formation and retrieval. Chronic stress and high levels of cortisol associated with depression can damage neurons in these areas.

“However, a further understanding of mechanisms linking memory decline and depression is crucial for developing targeted interventions aimed at improving mood and slowing cognitive decline in individuals with depression and memory impairment.”

People who started with higher depressive symptoms were more likely to experience faster memory decline later, while those who started with poorer memory were more likely to experience a later increase in depressive symptoms.

Those who experienced more of an increase in depressive symptoms during the study were more likely to have a steeper memory decline at the same time, and vice versa – those who had a steeper memory decline were more likely to have a sharper increase in depressive symptoms.

The pattern was not found for verbal fluency, however. While less verbal fluency was linked to more depressive symptoms at the start of the study, changes in one did not predict later changes in the other.