Cognitive dysfunction is a core feature of MDD which often persists even when patients are in remission

Decades of research and study provide evidence that cognitive dysfunction is a core feature of MDD which often persists even when patients are in remission following an acute episode. Clinicians in daily practice – while often attune to, and observant of, altered cognitive function in their patients with MDD – have often lacked the tools or the know-how to effectively assess and monitor this aspect of their patient’s condition.

Not niche: common-place

According to Dr Hamish McAllister-Williams of the Institute for Clinical Psychopharmacology at the University of Newcastle in the UK, far from being just an area of academic or niche interest, cognitive dysfunction is something that clinical practitioners need to understand and look for, since it has a global impact on patient function and recovery. Cognitive dysfunction in MDD patients includes impairments in attention, memory and executive function and may, according to Dr McAllister-Williams, be a consequence of underlying dysfunction in attention and processing speed.

Dr Mahomedy Zubeida, a psychiatrist in clinical practice in South Africa offered her personal “ABC” guide to looking for and helping patients who are affected the cognitive impact of MDD.

Lessons from history

Build a picture and collect the patient-story of how and when signs of cognitive dysfunction appear

She encouraged delegates not to forget their core history-taking skills when trying to build a picture and collect the patient-story of how and when signs of cognitive dysfunction appear and affect the person with MDD. In addition to looking at comorbid illnesses and factors that might in some way account for cognitive changes (comorbid psychiatric diagnoses; substance-use including alcohol and codeine consumption), she encouraged physicians to gather collateral information from patients’ family and friends.

Armed with insights

Armed with these core insights, she said the next step was to use very specific questions to explore with patients the ways in which cognitive dysfunction manifests – their struggles to concentrate, ability to perform well at work, their coping with everyday tasks – and to try to determine whether such dysfunction was temporary or persistent. Having gathered such case-based information, Dr Zubeida said the next step was to know what to do for the good of the patient.

Professor Raymond Lam of the University of British Columbia, Canada, who chaired the Expert exchange session, was keen to convey to delegates that there are simple tools they can employ in practice to both ‘diagnose’ cognitive dysfunction and track changes in cognitive function over time and during active patient management and treatment.

Tools of the trade

While Professor Lam focused on patient-reported problems, Dr Judith Jaeger provided an expert overview of a simple and robust method for measuring cognitive dysfunction. Dr Jaeger is an expert in neuropsychological tests designed to capture and record changes in cognitive function. She said her ‘desert-island’ simple test that tells a lot about cognitive dysfunction in MDD – the test she would choose if there was nothing else available – is the digit symbol substitution test (DSST).

In just minutes, the DSST can give a reliable, stable and meaningful measure of cognitive dysfunction, according to Dr Jaeger. First devised in the early 20^th century and used to assess the impact head injury in First-world-war soldiers, the DSST is as useful today as it was over 100 years ago, said Dr Jaeger.

Having an effect

Speakers at the session stressed the importance of using both subjective and objective measures of cognitive change in their patients as ways to catalogue and monitor changes over time. Dr Jaeger said that decline and change need to be viewed differently: changes in one patient may not be as important as changes in another – and what physicians need to look at are patterns of change. Drs McAllister-Williams and Jaeger also told delegates to bear in mind that while the cognitive changes that can be measured in patients with MDD may not seem large in terms of effect size when compared with those affecting people with dementia, their impact on function is considerable. For example the impairment typically seen using the DSST to assess cognitive impairment in MDD patients, corresponds to a blood alcohol concentration of 0.088 also as measured using the DSST tool.

Professor Lam encouraged delegates to look to the work of the THINC® Task Force  –  and the THINC-it® tool (which includes a version of the DSST and encompasses objective and subjective tests) which can be downloaded for free for use in clinical practice for diagnosis and assessment of cognitive dysfunction in patients with MDD.