The complexion and complexity of depression

Low mood and anhedonia are key symptoms of depression. That isn’t in doubt. Yet when diagnosing and assessing major depressive disorder (MDD), thinking about prioritizing symptoms for cure, or looking to define remission - subtle complexities and different faces of MDD clearly emerge.

Speaking during a symposium chaired by Professor Berhard Baune (Australia) called “Defining remission in depression: Is MADRS enough?” Professor Koen Demyttenaere of the Katholieke Universiteit Leuven, Belgium urged delegates to remember that depression is more than just low mood.

He highlighted that current DSM-5 criteria, while mood-focussed, do include other features such as the impact of MDD on ability to think, concentrate and be decisive, but he also noted that the criteria allow a single label – MDD – to be applied to patients with very different, or even no, features and symptoms in common. For example he noted that the symptoms of insomnia or hypersomnia are compounded in the criteria – despite being very opposite in their effect on patients – and he said that cognitive deficits, common in depression, could be overlooked.

Shine a light and look closer

Turning to definitions of remission of depression and assessment of treatment responses, Professor Demyttenaere, was also keen to note that scales such as the MADRS might fail to capture or focus on features of MDD that patients consider important to restore function and meaning in life. He said that so much depends on where you ‘shine the light’.

He reminded delegates that what matters for one patient may be different for another, and what a clinician considers key goals may not mirror the patient’s wish-list. Professor Demyttenaere reported on a survey showing that when clinicians and patients were asked to rank 10 features or symptoms of depression for remission, they had quite different priorities. The predominant concerns of physicians were alleviating negative mood and restoring function. Professor Demyttenaere described patient priorities as looking like the ‘photographic negative’ to this clinical picture – patients were more concerned with positive affects and ability to concentrate and function.

This led Professor Demyttenaere to briefly touch on a patient’s ‘persona and anima’ and how a patient’s character and beliefs, the nature of their depression and a number of sociodemographic variables can have a major impact on how well they respond to treatment – features that are not taken into account in any rating scales or assessments of MDD.

Mood and cognitive dysfunction in depression

Cognitive dysfunction has been recognized as an important feature of MDD since its earliest historical descriptions, as Dr Judith Jaeger, President and Senior Scientist at CognitionMetrcis LLC, Wilmington, USA reminded delegates during a presentation which touched upon the effect of antidepressant therapies on this often disabling feature of depression.

Dr Jaeger noted that there is evidence that some antidepressants can offer improvements in cognitive dysfunction, through effects that may be partially independent of mood effects.

Professor Catherine Harmer of the Department of Psychiatry at Oxford University in the UK, also shared insights on this topic, noting that in patients with depression – cognitive dysfunction can include bias towards negative emotional information as well as deficits in memory, attention and executive function.

She described recent evidence which suggests that antidepressant treatments may target ‘hot’ cognitive functions – ie certain memory and perceptive functions which are influenced by affective inputs – very early in the course of treatment.

Professor Harmer also described studies looking at ‘cold’ cognition – the more fundamental cognitive functions like attention and concentration  - and how these may also be affected in depression. She described rumination for example as a failure or inability to switch off from certain thoughts, likening this to revving an engine in the hope of stopping it stalling. Professor Hammer said that studies involving objective measures of cognitive function, including behavioural assessments and neuroimaging, are helping unlock some of the neural pathways and circuits important to cognitive dysfunction in depression and are already identifying differences in the ways in which antidepressant treatments may both acutely and in the long term impact on cognitive deficits in MDD.