Depression 04 Sep, 2017 Read Time: 3 mins

Assessing cognition in depression

Can cognitive symptoms in depression be quantified? 

We know that depression is made up of emotional, physical and cognitive symptoms.1 The latter are increasingly recognised as a significant component of depression in many patients, but are often poorly understood in clinical practice.2,3 Tools that give you the ability to assess and quantify cognitive dysfunction are essential in determining the severity of your patients’ depression.4

The importance of measuring cognitive dysfunction in depression
The cognitive symptoms of depression can have a devastating effect on patients’ day-to-day lives, and have been implicated as a principal mediator of psychosocial impairment, particularly with regards to performance at work.5,6

Cognitive dysfunction is also associated with the risk of relapse, with one study showing that more than 75% of patients with residual cognitive symptoms relapsed within 10 months of achieving remission.7

Monitoring cognition (as well as emotion) from the initial diagnosis of depression ensures that all aspects of your patient’s condition are duly considered. This in turn enables you take steps to prevent future relapses and help your patients achieve a true and lasting remission.4

In one study, 75% of patients with residual cognitive symptoms relapsed within 10 months of achieving remission7

Using the right tools for the job
THINC-it is a newly validated screening tool, and the first digital screening tool for cognitive dysfunction to be validated as a composite of objective and subjective scales in patients with depression.9

There are also a number of traditional tools available to help you assess and quantify the cognitive symptoms of depression. These include a range of objective neuropsychological assessments, as well as subjective scales and questionnaires.9 Those that are administered by a healthcare practitioner are known as ‘clinician-rated’, while those completed by the patients themselves are termed ‘patient-rated’. 

Table
Clinician-rated
Patient-rated

THINC-it: THINC-it is a cognitive screening tool that combines several objective measures with one subjective measure. Working memory is assessed using the n-back task, attention by the Choice Reaction Time task, executive function by the Trail Making Test-B and general cognition by the Digit Symbol Substitution Test. These objective tests can be usefully supplemented by subjective data obtained from the PDQ-5. THINC-it can be used on desktop and tablet computers, requires non-expert administration and yields simple data reporting.8

DSST: The patient is provided with a sheet containing a digit: symbol code whereby each of nine numbers is matched with a different symbol. On the same sheet, a series of digits from the code are presented in a random order. The patient must then draw the symbol that correctly corresponds to each digit, attempting to correctly match all nine to their corresponding symbols in a 90 second period. The number of correctly matched digit: symbol combinations is used to indicate performance, with more correct matches correlating with greater cognitive performance.10

RAVLT: A physician reads a series of 15 words, and the patient must repeat as many as they can remember, in any order. This is then repeated five times, using the same series each time.11 A second series of words is then read aloud, and the patient is given one chance to recall as many words as possible from this list. Following this, the patient is then asked to recall as many words as possible from the first list. The patient can achieve a maximum possible score of 75, gaining one point for every word successfully recalled from the first series, with higher scores indicating greater cognitive performance. A separate maximum score of 15 can be achieved from the delayed recall aspect of this test, whereby the patient achieves one point for each word they can remember from the first series, following completion of the second set of words. The delay in this assessment will depend on the time taken for the patient to complete five rounds of recall from the first series of words, coupled with the time taken to recall as much of the second series as possible. Higher total scores indicate greater cognitive functioning.12

CRT: The patient is asked to select either the right or left button on a pressure pad, depending on which side of the screen a stimulus appears following a random delay.13 This is repeated 80 times, and scoring is determined by the mean reaction time, with greater scores indicating more severe attention deficit.14

N-back test: The patient is required to recognise when a stimulus appears on a screen and record its location using the arrow buttons on a keyboard. 25 of these trials constitutes one series. The patient then repeats this test, but now records the location of the stimulus one step behind the sequence of stimulus locations displayed on screen – this is the 1-back test. This continues up to three steps behind that displayed, gradually increasing working memory load with each step. Patients produce final scores for both accuracy and reaction time, with lower accuracy and greater reaction times indicating more severe impairment of working memory.15

SRT: The patient is required to click as soon as they see a stimulus appear on a screen following a random delay. This test comprises two series of 50 trials each, with a short break between the series to give the patient a brief rest. Upon completion of the assessment, the patient’s mean reaction time can be calculated, with greater time indicating more severe impairment.16

Stroop test: The patient is required to read as many words as possible off a card within a 45 second period. They then must do the same with a second card on which a number of X’s are written, and name the colour of the ink in which each X is written. Finally, a third test requires patients to read a card on which a number of colours are written, but to name the ink colour of each word, rather than the written colour itself.15 Scores are determined by the number of items completed correctly within the time limit for each test, with lower scores indicating greater deficit in executive function.17

PDQ: A 20-item, patient-reported assessment of cognitive impairment in which each item is scored on a scale of 0 (never) to 5 (almost always), depending on how much each statement relates to the patient’s own experiences. The maximum possible score on the PDQ is 100, with higher scores indicating more severe cognitive dysfunction.18

CPFQ: Each of the seven most common aspects of cognition is assessed on a patient-rated scale from 1 (greater than normal) to 6 (totally absent), providing a maximum total score of 4219 with scoring brackets as below:20

  • ≤7: Greater than normal functioning
  • 8–14: Normal functioning
  • 15–21: Minimally diminished functioning
  • 22–28: Moderately diminished functioning
  • 29–35: Markedly diminished functioning
  • 36–42: Totally absent functioning

While the above is by no means a definitive list of all the tools that can be used to assess cognitive dysfunction, they do cover the fundamental aspects that your patients with depression may be experiencing. Using these tools routinely in your clinical practice will enable you to monitor cognitive symptoms in your patients living with depression and help to keep them on the road to recovery.4

References

  1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Health Disorders. 5th Washington, DC: American Psychiatric Association; 2013.
  2. Conradi HJ et al. Psychol Med 2011; 41(6): 1165–1174.
  3. Jarema M et al. Psychiatr Pol 2014; 48(6): 1105–1116.
  4. Greer TL et al. CNS Drugs 2010; 24(4): 267–284.
  5. McIntyre RS et al. Depress Anxiety 2013; 30(6): 515–527.
  6. Lam RW et al. Can J Psychiatry 2014; 59(12): 649–654.
  7. Paykel ES et al. Dialogues Clin Neurosci 2008; 10: 431–437.
  8. McIntyre RS. Validation of the THINC-it® screening tool. Presented at the 29th ECNP Congress 2016; Vienna, Austria.
  9. Cusin C et al. Rating Scales for Depression. In: Handbook of Clinical Rating Scales and Assessment in Psychiatry and Mental Health. Ed: Baer, Lee, Blais, Mark A. (Eds.), 2010. 
  10. McLeod DR et al. Behav Res Methods Instrum 1982; 14(5): 463–466.
  11. Schmidt M. Rey auditory verbal learning test: a handbook. Los Angeles Western Psychological Services 1996.
  12. Barzotti T et al. Arch Gerontol Geriatr Suppl 2004; 9: 57–62.
  13. Cambridge Cognition. Choice Reaction Time (CRT). Available at:http://www.cambridgecognition.com/tests/choice-reaction-time-crt. Accessed July 2015.
  14. Cogtest. Choice Reaction Tim. Available at:http://www.cogtest.com/tests/cognitive_int/crt.html. Accessed July 2015.
  15. Miller KM et al. Arch Clin Neuropsych 2009; 24: 711–717.
  16. Cogtest. Simple Reaction Time Test. Available at: http://www.cogtest.com/tests/cognitive_int/srt.html. Accessed July 2015.
  17. Culpepper L. Cognition in MDD: Implications for primary care. In: Cognitive dysfunction in major depressive disorder. Ed: McIntyre R, Cha D, 2015.
  18. Lovera J et al. J Rehabil Res Dev 2006; 43(1): 73–82.
  19. Fava M et al. Psychother Psychosom 2009; 78: 91–97.
  20. Roffman JL et al. Chapter 6: Diagnostic rating scales and psychiatric instruments. In: Massachusetts General Hospital Comprehensive Clinical Psychiatry. Ed: Stern TA, Fava M, Wilens TE, Rosenbaum JF, 2008.