A newly-published study has found a link between repeated episodes of anxiety and depression experienced in the first four decades of life, and a decline in memory function by the time a person reaches their 50s. The researchers behind the study have called for the UK government to invest in better protecting the well-being of young adults to help safeguard the brain health of the country's ageing population.

The data used in the study was collected as part of the National Child Development Study (NCDS). The project collected information from 18,558 participants born in England, Scotland and Wales in 1958. Between the ages of 7 and 50, volunteers were periodically tested for depression and anxiety.

Following its analysis of the data, the UK-based team discovered that a single instance of depression or anxiety wasn't associated with a huge loss of memory function in midlife. However, individuals that experienced a series of depressive episodes over the course of multiple decades were found to have significantly decreased memory function by the time that they were 50. While this could be a case of the former causing the latter, it's also possible that both conditions could have a common cause.

"We knew from previous research that depressive symptoms experienced in mid adulthood to late adulthood can predict a decline in brain function in later life but we were surprised to see just how clearly persistent depressive symptoms across three decades of adulthood are an important predictor of poorer memory function in mid-life," comments University of Sussex Psychology PhD student and co-author of the new study, Amber John.

Although there was a clear correlation between anxiety, depression and memory problems, the episodes appeared to have little effect on other cognitive functions, such as information processing speed and verbal fluency. However, according to the team, depressive episodes and the associated memory loss could be an indicator for dementia in later life.

The researchers note that their study had a number of limitations. For example, cognitive function was only assessed at one point in adulthood in the NCDS when volunteers reached 50 years of age, rather than throughout the process. The lack of data makes it more difficult to assess the effects that depressive events may have on memory over time. Furthermore, the tests used to measure cognitive decline were also fairly limited in scope.

The authors also expressed the need for future research to shed light on the biological and sociobehavioral factors that may underpin the link between anxiety, depression and cognitive decline, and called on the government to better protect young adults.

"With the publication of this research, we're calling for the government to invest in mental health provision to help stem the risk of repeated episodes of depression and anxiety," said John. "From an individual's perspective, this research should be a wake-up call to do what you can to protect your mental health, such as maintaining strong relationships with friends and family, taking up physical exercise or practicing mindfulness meditation – all of which have been shown to boost mental health ... Then of course, seeing your GP for advice if you feel you need help with depression or anxiety."

The research has been published in the British Journal of Psychiatry.