Cognition, depression and cognitive changes in Major Depressive Disorder: a brief consideration

Carolina received her Psychology, Clinical and Cognitive Neuroscience bachelors degree from Royal Holloway University of London and she has recently obtained a MSc degree in Translational Neuroscience from Imperial College London: Cognition is extremely fascinating. It is my belief that understanding how we learn is the key to self-actualisation.

 

Cognition is a term that refers to all the mental processes involved in the interpretation of the environment, including overt behaviours and emotional states, by mean of sensory experience (Neisser, 2014). For example, while watching a rugby match, we may interpret a physical contact between two players as being painful based on the visual information of a bleed and on the emotional reaction of a cry. The mental processes supporting the production of deliberate actions are also components of cognition (Neisser, 2014). Reaching for an object, for instance, would require focused attention to the target and online adjustments of the body position in the space relatively to the object.

Cognitive abilities are a determinant aspect of quality of human life. Reports suggest that cognitively skilled children obtain more prestigious occupations later in life (Cheng & Furnham, 2012) and a significant portion of variability in academic achievement in adulthood is explained by general cognitive ability (Rohde & Thomposon, 2007). In the elderly population, good cognitive functioning is associated with more satisfactory interpersonal relationships (Watanabe et al., 2016), engagement in social activities, hobbies, sports, volunteering, and generally more diversified daily activities (Fu et al., 2018).

Aging is accompanied by a cognitive deterioration that differently affects fluid and crystallised abilities (Cattell, 1943). The former comprise reasoning skills employed to solve mental operations and tasks (Murman, 2015), such as inferring the fastest bus route to approach a specific city district. Crystallised abilities constitute instead cumulative knowledge (i.e. facts) and experience acquired in the course of time (Murman, 2015). In 2009, a large cross-sectional study revealed that while fluid skills constantly deteriorate from late adolescence, crystallised abilities increment along with age, reaching a plateau in the 60s (Salthouse, 2009).

Cognition is, in part, genetically determined (Hill et al., 2014). However, a wide range of modifiable environmental factors can ‘accelerate’ or ‘attenuate’ cognitive decline. Interpersonal relationships contribute to maintain cognitive health by promoting social identification and support (Haslam et al., 2016). Furthermore, cognitive functioning is supported by higher levels of education, socioeconomic status and intellectual activity (Parisi et al., 2012). Nonetheless, various environmental risk factors can negatively affect cognition, such as smoking (Waisman Campos et al., 2016), a poor diet (Shatenstein et al., 2012) and low levels of physical activity (Kelly et al., 2014).

Cognitive functions can also be affected by depression. Major depressive disorder (MDD) is a common psychiatric disorder that negatively affects mood, thoughts and behaviours, compromising the ability to function both at work and at home. It is characterised by symptoms including low mood, loss of interest, fatigue, appetite changes, suicidal thoughts, difficulty thinking and irritability, for a period of time of at least 2 weeks (American Psychiatric Association, 2013). Major depression is one of the most disabling illnesses: it contributes to early mortality causing 60% of worldwide suicides (World Health Organization, 2009) and it has elevated annual pharmaceutical costs (Kessler, 2012), thus constituting a major global social and economic concern.

The onset of MDD typically occurs in late adolescence, and it is more prevalent among women than men (Hasin et al., 2018). It annually affects ~6.7% individuals, and ~16.6% of the population experience it at least once it in their life (Kessler et al., 2005). Importantly, depression not only represents a risk factor of accelerated cognitive decline, but it affects cognitive functioning in the everyday-life experience. Depressed individuals are more likely to ‘misinterpret’ neutral faces as expressing anger (Watters & Williams, 2011) compared to healthy controls. The ‘tendency’ towards negative emotions in depression is moreover accompanied by a lower ‘reactivity’ to positive stimuli, whereby hedonic pictures are considered to be less pleasant and less arousing compared to healthy subjects (Sloanab et al., 1997).

Furthermore, depression is generally linked to deficits of memory (Burt et al., 1995) including a decreased recognition and retrieval of previously learned words (Brand et al., 1992), visuomotor ability, such as a reduced horizontal eye-movements span (Deijen et al., 1993), but also mental flexibility (Airaksinen et al., 2004), language fluency (Reischies & Neu, 2000), abstract reasoning (Naismith et al., 2003) and decision-making, with an increased risk of impulsively engaging in pleasurable activities with harmful consequences (Chamberlain & Sahakian, 2006).

What is the impact of existent therapies on depression and cognition?

Recently, the effect of three different antidepressant drugs has been tested on patients with MDD and diminished functioning in seven cognitive domains including attention, verbal memory, mental flexibility, decision-making and information-processing (Shilyansky et al., 2016). The results showed that while all the antidepressants succeeded in improving mood-related symptoms, their effectiveness on cognition was limited to only two domains: mental flexibility and executive functions, namely organizing and planning skills. Talking treatments, such as the cognitive behavioural therapy, have been shown to improve the clinical symptoms of depression (Twomey et al., 2014), although their impact on cognitive dysfunctions are yet to be explored.

This is an exciting research avenue for the future: further investigations are required to delineate the distinct components of cognition, to elucidate the nature and extent of the cognitive changes in depression, as well as, to develop novel approaches to address specific deficits.

References

Airaksinen, E, Larsson, M, Lundberg, I and Forsell, Y (2004) Cognitive functions in depressive disorders: evidence from a population-based study. Psychological medicine34(1):83-91.

American Psychiatric Association (2013) Diagnostic and statistical manual of mental disorders (DSM-5). American Psychiatric Pub.

Brand, AN, Jolles, J and Gispen-de Wied, C (1992) Recall and recognition memory deficits in depression. Journal of affective disorders25(1):77-86.

Burt, DB, Zembar, MJ and Niederehe, G (1995) Depression and memory impairment: a meta-analysis of the association, its pattern, and specificity. Psychological bulletin117(2): 285.

Cattell, RB (1943) The measurement of adult intelligence. Psychological Bulletin40(3):153.

Chamberlain, SR and Sahakian, BJ (2006) The neuropsychology of mood disorders. Current psychiatry reports8(6):458-463.

Cheng, H and Furnham, A (2012) Childhood cognitive ability, education, and personality traits predict attainment in adult occupational prestige over 17 years. Journal of Vocational Behavior81(2):218-226.

Deijen, JB, Orlebeke, JF and Rijsdijk, FV (1993) Effect of depression on psychomotor skills, eye movements and recognition-memory. Journal of affective disorders29(1): 33-40.

Fu, C, Li, Z and Mao, Z (2018) Association between social activities and cognitive function among the elderly in China: a cross-sectional study. International journal of environmental research and public health15(2): 231.

Kelly, ME, Loughrey, D, Lawlor, B.A., Robertson, I.H., Walsh, C. and Brennan, S. (2014) The impact of cognitive training and mental stimulation on cognitive and everyday functioning of healthy older adults: a systematic review and meta-analysis. Ageing research reviews15:28-43.

Hasin, DS, Sarvet, A.L., Meyers, JL, Saha, TD, Ruan, WJ, Stohl, M and Grant, BF (2018) Epidemiology of adult DSM-5 major depressive disorder and its specifiers in the United States. JAMA psychiatry75(4): 336-346.

Haslam, C, Cruwys, T, Milne, M, Kan, CH and Haslam, SA (2016) Group ties protect cognitive health by promoting social identification and social support. Journal of aging and health28(2):244-266.

Hill, WD, Davies, G, Van De Lagemaat, LN, Christoforou, A., Marioni, RE, Fernandes, CPD, Liewald, DC, Croning, MD, Payton, A, Craig, LC and Whalley, LJ (2014) Human cognitive ability is influenced by genetic variation in components of postsynaptic signalling complexes assembled by NMDA receptors and MAGUK proteins. Translational psychiatry4(1):e341.

Kessler, RC (2012) The costs of depression. Psychiatric Clinics35(1):1-14.

Kessler, RC, Berglund, P, Demler, O, Jin, R, Merikangas, KR and Walters, EE (2005) Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Archives of general psychiatry62(6):593-602.

Leykin, Y, Roberts, CS and DeRubeis, RJ (2011) Decision-making and depressive symptomatology. Cognitive therapy and research35(4):333-341.

Murman, DL (2015) The impact of age on cognition. Seminars in hearing 36(3): 111. Thieme Medical Publishers.

Naismith, SL., Hickie, IB., Turner, K, Little, CL, Winter, V, Ward, PB, Wilhelm, K, Mitchell, P and Parker, G (2003) Neuropsychological performance in patients with depression is associated with clinical, etiological and genetic risk factors. Journal of clinical and experimental neuropsychology25(6): 866-877.

Neisser, U (2014) Cognitive psychology: Classic edition. Psychology Press.

Parisi, JM, Rebok, GW, Xue, QL, Fried, LP, Seeman, TE, Tanner, EK, Gruenewald, TL, Frick, KD and Carlson, MC (2012) The role of education and intellectual activity on cognition. Education, 15:19

Reischies, FM and Neu, P (2000) Comorbidity of mild cognitive disorder and depression–a neuropsychological analysis. European archives of psychiatry and clinical neuroscience250(4):186-19

Rohde, TE and Thompson, LA (2007) Predicting academic achievement with cognitive ability. Intelligence35(1):83-92.

Salthouse, TA (2009) Decomposing age correlations on neuropsychological and cognitive variables. Journal of the International Neuropsychological Society15(5):650-661.

Shatenstein, B, Ferland, G, Belleville, S, Gray-Donald, K, Kergoat, MJ, Morais, J, Gaudreau, P, Payette, H and Greenwood, C (2012) Diet quality and cognition among older adults from the NuAge study. Experimental gerontology47(5):353-360.

Shilyansky, C, Williams, LM, Gyurak, A, Harris, A, Usherwood, T and Etkin, A (2016) Effect of antidepressant treatment on cognitive impairments associated with depression: a randomised longitudinal study. The Lancet Psychiatry3(5):425-435.

Twomey, C, O’Reilly, G and Byrne, M (2014) Effectiveness of cognitive behavioural therapy for anxiety and depression in primary care: a meta-analysis. Family practice32(1): 3-15.

Waisman Campos, M, Serebrisky, D and Mauricio Castaldelli-Maia, J (2016) Smoking and cognition. Current drug abuse reviews9(2):76-79.

Watanabe, K, Tanaka, E, Watanabe, T, Chen, W, Wu, B, Ito, S, Okumura, R and Anme, T (2016) Association between Social Relationships and Cognitive Function among the Elderly. Public Health Research6(2):59-63.

Watters, AJ and Williams, LM (2011) Negative biases and risk for depression; integrating self‐report and emotion task markers. Depression and anxiety28(8):703-718.

World Health Organization (2009) Depression: A global public health concern, Accessed 28 May 2018, <http://www.who.int/mental_health/management/depression/who_paper_depression_wfmh_2012.pdf>

 

Picture credits: Wellcome Collection

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