Elsevier

Psychiatry Research

Volume 176, Issues 2–3, 30 April 2010, Pages 183-189
Psychiatry Research

The role of cognitive impairment in general functioning in major depression

https://doi.org/10.1016/j.psychres.2008.12.001Get rights and content

Abstract

The association between cognitive performance and general functioning in depression is controversial. The present study evaluated the association between cognitive dysfunction and major depressive disorder (MDD, N = 70) as compared with age- and gender-matched healthy controls (n = 206) and its relationship to general functioning (physical and mental health quality of life, activities of daily living, and employment status) in participants with current MDD (n = 26) and those with previous MDD only (n = 44). Participants were assessed clinically using the Mini International Neuropsychiatric Interview (M.I.N.I.) for the depression groups and the Diagnostic Interview for Psychoses (DIP-DM) for the control group. Measures to evaluate cognition and quality of lifes comprised the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), the Short Form-36 Health Survey Questionnaire, and the Activities/Instrumental Activities of Daily Living (ADL/IADL); employment status was also assessed in MDD. The results showed that a) while individuals with current depression had worse cognitive performance in all domains than healthy controls, those individuals with previous depression had lasting cognitive impairments in the domains of immediate memory and attention as compared with healthy controls; b) individuals with current depression had lower scores in the visuospatial/constructional and attention domains and the total score than individuals with previous depression; c) individuals in the depression group as a whole who were currently unemployed had significantly lower scores in all domains (except attention) of cognitive function; d) cognitive function was not related to either physical or mental quality of life or impairments of activities of daily living (ADL, IADL); e) that unemployment in previous depression was related to poor cognitive function similar to those with current depression. The results indicate that MDD may have detrimental and lasting effects on cognitive performance partly related to poorer general functioning.

Introduction

Depression is a severe and common psychiatric disorder affecting millions of people worldwide (Murray and Lopez, 1996, Ustun et al., 2004, Andrews et al., 2005). Although this psychiatric disorder primarily involves mood disturbances, cognitive impairment is now a well-established feature of major depression (Austin et al., 1992, Austin et al., 2001, Den Hartog et al., 2003, Porter et al., 2007). Although the exact neuropsychological profile remains to be fully elucidated, research has shown neurocognitive deficits in patients with depressive disorders in the following cognitive domains: executive functioning (Elliott et al., 1997, Austin et al., 1999, Paelecke-Habermann et al., 2005, Porter et al., 2007), attention and attentional set shifting (Purcell et al., 1997, Ravnkilde et al., 2002), memory (Austin et al., 1992, Harmer et al., 2002), visuo-spatial processing and psychomotor function (Mondal et al., 2007). Further evidence would suggest that the cognitive function in patients with recurrent depression declines with each successive episode of depression (Basso and Bornstein, 1999, Stordal et al., 2004). Research by Airaksinen et al. (2004) would also suggest that depressed patients display decreased cognitive functioning long after the remission of depressive episodes. Such evidence suggests that there may be pervasive and long-lasting effects of depression on cognitive ability; although this association remains to be fully clarified (Miller et al., 1991, Grant et al., 2001). Moreover, there is now evidence to suggest that these persistent neurocognitive deficits might impact the ability for some individuals with depression to functionally recover (Jaeger et al., 2006).

Since research in depression has traditionally investigated the impact of depressive symptoms on quality of life (Meltzer-Brody and Davidson, 2000), little is known about the relationship between cognitive impairment associated with depression and general functioning and quality of life. In brief, it has been shown that an increase in depressive symptoms is associated with a decrease in quality of life (Vaughn McCall et al., 1999, Gostautas et al., 2006), and that chronic recurrence of depression is associated with prolonged dysfunction (Schwenk et al., 2004). Furthermore, a recent study suggests that the relationship between depression and impaired activities of daily living (IADL) is mediated by deficits in executive function (Kiosses and Alexopoulos, 2005).

In the context of functioning in depression, it is important to note that after treatment a large number of patients remain partly symptomatic (50% of treated cases achieve full remission), experiencing decreased social activities, work performance and well-being (Zajecka, 2003). Furthermore, reduced general functioning and performance in non-remitted depression causes an economic burden with direct treatment costs that are up to 49% higher than in fully remitted patients in the first year after the depressive episode (Simon et al., 2000). The role of cognitive dysfunction in the relationship between work performance and remission of depression remains unclear. More insight into the mediating role of cognitive dysfunction in general functioning among depressed patients might have far-reaching implications for the treatment and management of depressive disorders, which currently focuses on reducing mood-related symptoms and not cognitive dysfunction.

Hence in the present study, the association between cognitive dysfunction and general functioning (physical and mental health quality of life (QoL), activities of daily living, employment status) in individuals with depression was evaluated. The specific aims of the study were:

  • 1.

    To investigate the association between cognitive dysfunction and MDD as compared with a healthy control group;

  • 2.

    To investigate the effects of current versus previous MDD on domains of cognitive function.

  • 3.

    To investigate the relationship between cognitive performance and quality of life, impairments in activities of daily living (IADL, ADL) and employment in MDD.

Section snippets

Depression sample

Participants were recruited from community and outpatients services in the Townsville Health Service District. Patients were re-contacted for the purpose of this study after they had been registered for current or previous depression. Each person gave written informed consent before the study began. Inclusion criteria for the study were 1) above the age of 18 and under the age of 80, 2) adequate reading and writing skills and the ability to speak the English language, and 3) current or history

Depression group

Of the 70 participants, the age range was from 20 years to 77 years (mean = 44.9, S.D. = 14.70) with no significant difference between females and males (P = 0.25). The gender ratio was 1.7 with 26 males (37.1%) aged from 23 to 71 years (mean = 47.6, S.D. = 15.6) and 44 females (62.9%) aged from 23 to 77 years (mean = 43.3, S.D. = 14.2). On average, participants had 11.0 years of education without showing differences across gender (female: mean = 10.9; S.D. = 1.2; male = 11.1; S.D. = 1.6; P = 0.49).

Table 1 presents

Discussion

The results of the current study showed that a) while individuals with current depression had worse cognitive performance in all domains as compared with healthy controls, those individuals with previous depression had lasting cognitive impairments in the domains of immediate memory and attention as compared with healthy controls; b) individuals with current depression had lower scores in the visuospatial/constructional and attention domains and the total score as compared with individuals with

Acknowledgements

The study was supported by an internal research grant of James Cook University. The Using our Brains donor program is supported by the National Institute on Alcohol Abuse and Alcoholism (NIAAA — grant no: R01AAA01272508).

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