A new large-scale longitudinal study carried out by University of Sussex psychologists has found a clear link between episodes of depression and anxiety experienced by adults in their twenties, thirties and forties, with a decrease in memory function by the time they are in their fifties. The study, published in the British Journal of Psychiatry, is the first of its kind to look at the relationship between depressive symptoms experienced across three decades of early-mid adulthood and a decline in cognitive function in midlife.

The Sussex psychologists analysed data from the National Child Development Study, which was established in 1958 with a cohort of over 18,000 babies and followed participants from birth into childhood and through to adulthood. The Sussex psychologists found that an accumulation of symptoms experienced by participants over the three decades provided a strong indicator of a linear decrease in memory function by the time the adults were fifty.

They found that one episode of depression or anxiety had little effect on the memory function of adults in midlife, regardless of which decade it was experienced, but that once the episodes increased to two or three over the course of the three decades, that this predicted a steady decrease in the participant's memory function by the time they reached fifty.

This, the psychologists from the EDGE Lab at the University of Sussex argue, highlights an opportunity to protect future memory function by promoting mental health interventions amongst young adults and they are calling on the UK government to invest in the mental health of young adults as a preventative measure to protect the future brain health of our ageing population.

Dr Darya Gaysina, Senior Lecturer in Psychology at the University of Sussex said: "We found that the more episodes of depression people experience in their adulthood, the higher risk of cognitive impairment they have later in life. This finding highlights the importance of effective management of depression to prevent the development of recurrent mental health problems with long-term negative outcomes.

"We'd therefore like to see the government investing more in the mental health provision for young adults, not only for the immediate benefit of the patients, but also to help protect their future brain health."

As well as memory, the psychologists also assessed verbal fluency, information processing speed and accuracy scores of the participants once they turned fifty. Encouragingly, episodes of depression and anxiety had little impact on the latter four areas of cognitive function but the associated loss of memory suggests that depressive symptoms experienced in early adulthood could predict dementia in older adulthood.

Previous research carried out by the EDGE lab at the University of Sussex had found a relationship between depressive symptoms experienced in older adulthood and a faster rate of cognitive decline, but this is the first time that such a large and UK nationally representative sample has been able to make this link in the first three decade of adulthood.

University of Sussex Psychology PhD student Amber John said: "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.

"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. 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."