Depression has many faces: impaired cognition an important feature

Observer-rated clinical scales in everyday use do not reflect the diversity in depressive symptoms. Nor do they assess those aspects of greatest concern to patients, Koen Demyttenaere, of the Catholic University of Leuven, Belgium, told the Florence meeting. Function should come more to the fore.

Negative and positive priorities

In a recent study, clinicians and patients with major depressive disorder (MDD) were asked what they expected from antidepressant treatment.¹ Physicians ranked highest the alleviation of negative symptoms. For patients, on the other hand, having a meaningful life, enjoying it, and feeling satisfied were the top features listed. 

Are doctors more comfortable with pain than with pleasure?

Factor analysis of data from the STAR*D and GENDEP studies suggests that a cluster of symptoms centred on interests and activities --  including enjoyment, concentration, ability to feel, activity,  energy and sex – is particularly important.² Baseline scores on this factor were the most robust predictor of outcome; and this was independent of the initial severity of depression.

In contrast, of the 27 items in the HAM-D and MADRS scales combined, only three relate to a patient’s work and interests, or slowness of thought and action, or impaired concentration. 

Professor Demyttenaere also drew attention to the distinction between remission – defined as a temporary and partial relief from symptoms – and recovery, implying the return to previous levels of health and strength. For our patients, symptomatic remission is not good enough, he suggested. And achieving restoration of function may require different approaches to treatment.

Cognitive dysfunction a critical determinant of outcome.

The theme was taken up by Roger McIntyre, of the University of Toronto, Canada.

Cognition a determinant of outcome

Why should we assess cognitive dysfunction in depression?, he asked. Well, because it is there. And because it has profound adverse effects. ³

Approximately half of people with MDD perform one standard deviation or more below the norm on the digit symbol substitution test (DSST). This is about two-thirds of the effect of a night’s total sleep deprivation. And there is evidence that cognitive symptoms mediate workplace outcomes to a greater extent than depression severity as measured by total score on the HAMD-17. Quality of life and social functioning are also affected.

We now have a practical tool sensitive in detecting impairment

Impaired cognition may also compromise the effectiveness of treatment since it risks interfering with adherence to pharmacotherapy and the capacity to learn during psychotherapy.

Accepting the relevance of cognition, the next question is how we should measure it. 

A validated screening tool

Traditionally, our ability to assess cognition has been limited since available comprehensive measures were time-consuming and required specialist interpretation. With the development of the THINC-it® tool, we now have a computerised and self-administered instrument – incorporating both objective and subjective elements -- that is available free of charge and suited to the setting of a busy office practice.

In a validation study submitted for publication, a hundred people with MDD were compared against a hundred matched controls. Forty-three percent of patients had a THINC-it® score that was at least one standard deviation below that of controls; and 82% of controls performed better than patients with MDD.

Cognitive dysfunction measured by THINC-it® is greater in individuals with depression who have concurrent pain. And the extent to which the scores of patients with MDD differ from those of healthy controls relates significantly to perceived deficits in psychosocial function measured by the Sheehan Disability Scale.

So we now have a practical tool sensitive in detecting cognitive impairment; and this is important since treatment options differ in their ability to mitigate cognitive dysfunction.

Productivity can remain impaired despite improved symptoms

Depression more than low mood

Real-world evidence of the consequences of cognitive dysfunction was assessed by Bernhard Baune (University of Adelaide, Australia).

Cognition is a relevant functional domain, especially in the workplace. In a study by Lam and colleagues, 52% of depressed patients reported that cognitive difficulty severely interfered with their occupational functioning. ⁴ This was evident in slowness of thinking, and poor concentration and executive function. Of people who have had depression and return to work, 50% take time off because of their depression.

Cognitive dysfunction needs to be targeted assertively

In the PERFORM study, around 1500 people with depression were followed up over two years.⁵ Despite being at work, this population had functional complaints relating to family and employment. And self-perceived cognitive complaints were associated with the severity of depressive symptoms and with impaired daily function. 

Absence from work is one thing. But society is also affected by the return to work of people who are there but do not perform very well – a phenomenon termed “presenteeism”, Professor Baune argued. There is potential for significant benefit, to individuals and to society, if cognitive functioning in MDD can be improved.

This is a clinical need we need to target assertively, he concluded.

THINC-it® can be downloaded here