Review
A review on cognitive impairments in depressive and anxiety disorders with a focus on young adults

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Abstract

Background

There is growing evidence for cognitive dysfunction in depressive and anxiety disorders. Nevertheless, the neuropsychological profile of young adult patients has not received much systematic investigation. The following paper reviews the existing literature on cognitive impairments in depressive and anxiety disorders particularly among young adults. Additionally, the focus of young adult age group and the effect of confounding variables on study results are discussed.

Methods

Electronic database searches were conducted to identify research articles focusing on cognitive impairments in depressive or anxiety disorders among young adults published in English during years 1990–2006.

Results

Cognitive impairments are common in young adults with major depression and anxiety disorders, although their nature remains partly unclear. Accordingly, executive dysfunction is evident in major depression, but other more specific deficits appear to depend essentially on disorder characteristics. The profile of cognitive dysfunction seems to depend on anxiety disorder subtype, but at least obsessive–compulsive disorder is associated with deficits in executive functioning and visual memory. The conflicting results may be explained by heterogeneity within study participants, such as illness status, comorbid mental disorders, and medication, and other methodological issues, including inadequate matching of study groups and varying testing procedures.

Limitations

The study is a comprehensive review, but not a formal meta-analysis, due to methodological heterogeneity.

Conclusions

Cognitive impairments are common in major depression and anxiety disorders. However, more research is needed to confirm and widen these findings, and to expand the knowledge into clinical practice. Controlling of confounding variables in future studies is highly recommended.

Introduction

The emergence of mental disorders – and the cognitive impairments related to them – in young adulthood may associate with serious and long-lasting psychosocial difficulties. Young adulthood is a key period for both prevention and treatment of mental disorders to avoid chronicity of the symptoms (Kessler et al., 2005, Newman et al., 1996). This paper reviews the existing literature on cognitive deficits related to depressive and anxiety disorders among young adults and discusses the impact of confounding variables on measurement of neuropsychological functioning.

Young adulthood is a risk period for the emergence of many psychiatric disorders (Kessler et al., 2005, Kim-Cohen et al., 2003). The incidence of mental disorders increases from childhood through mid-adolescence and peaks in late-adolescence and young adulthood (Newman et al., 1996). The prevalence estimates of mental disorders are relatively consistent in young adult cohorts (in epidemiological studies, defined usually between 18 and 35 years of age) in industrial countries, using DSM-criteria (APA, 1994): Prevalence estimates of 17–24% for 1 month (Aalto-Setälä et al., 2001, Regier et al., 1993), 38–48% for 1 year (Feehan et al., 1994, Kim-Cohen et al., 2003, Newman et al., 1996, Turner and Gil, 2002) and 52–61% for lifetime (Kessler et al., 2005, Turner and Gil, 2002) have been reported for mental disorders in general, with anxiety disorders, mood disorders, and substance use disorders being the most prevalent ones. Women are more likely to be diagnosed with depressive and anxiety disorders, and men with substance use disorders (Aalto-Setälä et al., 2001, Feehan et al., 1994, Kessler et al., 2005, Newman et al., 1996, Regier et al., 1993, Turner and Gil, 2002). Table 1 summarizes the prevalence rates of specific depressive and anxiety disorders observed in epidemiological studies of young adult cohorts in industrial countries. The high prevalence estimates indicate that depressive and anxiety disorders are major public health problems for this age group.

Only about one third of young adults with mental disorders seek professional help (Aalto-Setälä et al., 2002), and this under-treatment is evident also for major depression in young adulthood (Haarasilta et al., 2003). It has been proposed that the phenomenology and nature of depression changes with age (Brodaty et al., 2005). Moreover, it has been suggested that early-onset depression represents a more serious form of the disorder: It leaves more psychosocial scars (Rohde et al., 1994) and is associated with a greater number of comorbid mental disorders (Rohde et al., 1991) than late-onset depression. Early- vs. late-onset anxiety disorders have also been hypothesized to be distinct forms of the disorders (Hemmings et al., 2004, Tükel et al., 2005). Moreover, having major depressive or anxiety disorder in young adulthood may double the risk for later substance abuse or dependence (Chilcoat and Breslau, 1998, Christie et al., 1988). Having depression during early parenting triples the risk for the offspring to develop an anxiety disorder, major depression or substance dependence (Weissman et al., 2006). These findings implicate that depression and anxiety may impact younger patients more severely than older.

In the context of psychiatric research, neuropsychological examination has been increasingly used in assessing the cognitive dysfunctions that are among the core features of several mental disorders (for a review, see Keefe, 1995). In a clinical setting, neuropsychological examination comprises an interview of the patient's background and present situation, a behavioral observation, and an administration of the neuropsychological tests (see Lezak et al., 2004). Information obtained from this examination can be used in the patient's treatment planning, evaluating the efficacy of the treatment, in differential diagnosis in certain cases, as well as for research purposes. In addition, it may be possible to differentiate which deficits are illness state-dependent and which are more fundamental trait abnormalities or vulnerability markers of certain disorders. These findings could have considerable implications for prevention and clinical management of these disorders, as cognitive deficits are indeed significant factors in affecting individual's ability to function socially and occupationally in everyday life.

Studies of psychiatric disorder-related cognitive impairments usually report use of well-known standard neuropsychological tests. Among the most used test batteries are the Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1997) and the Wide Range Achievement Test (WRAT; Jastak and Wilkinson, 1984), which are used to estimate individual's general intelligence, and the Wechsler Memory Scale (WMS; Wechsler, 1987), which consists of subtests measuring several subfunctions of memory performance. Also, the Cambridge Neuropsychological Test Automated Battery (CANTAB; Robbins et al., 1994) and the Luria-Nebraska Neuropsychological Battery (LNNB; Golden et al., 1985) are among the most used test batteries to evaluate various components of cognition. For measuring verbal memory and learning, the California Verbal Learning Test (CVLT; Delis et al., 1987) and the Rey Auditory Verbal Learning Test (RAVLT; Schmidt, 1996) are most commonly used. Non-verbal long- and short-term memory is often measured with the Rey–Osterrieth Complex Figure Test (ROCFT; Meyers and Meyers, 1995) and the Benton Visual Retention Test (BVRT; Sivan, 1992). The Trail Making Test (TMT; Reitan and Wolfson, 1993), the Wisconsin Card Sorting Task (WCST; Heaton, 1981), the Stroop Color Word Interference Test (SCWIT; Golden, 1978), the Continuous Performance Test (CPT; Conners, 2000), the Paced Auditory Serial Addition Test (PASAT; Gronwall, 1977), and the Controlled Oral Word Association Test (COWAT; Benton and Hamsher, 1989) are used to measure attentive and executive functioning.

It is of high relevance to study features that may associate with and function as mediating factors to depressive and anxiety disorders in young adulthood. Thus far, research has provided very little information concerning the pattern, nature and extent of cognitive dysfunction involved in mental disorders particularly among young adults. This review aims to aggregate and evaluate in detail the existing literature on cognitive deficits in major depressive and anxiety disorders among young adult patients.

Section snippets

Methods

Electronic PubMed and PsycInfo searches were conducted to identify research articles that focus on cognitive findings in depressive or anxiety disorders in young adulthood and were published in English language during years 1990–2006. Different forms and combinations of the following search terms were used: depression, dysthymia, anxiety, panic disorder, phobia, generalized anxiety disorder, post-traumatic stress disorder, obsessive–compulsive disorder, neuropsychology, cognitive

Which cognitive domains are impaired in depressive disorders?

Most of the studies investigating the association between depression and cognitive dysfunction have been conducted among middle-aged and elderly patients (for a review, see Kindermann and Brown, 1997), or among patients regardless of their age (for a review, see Austin et al., 2001, Veiel, 1997, Zakzanis et al., 1998). In addition, there are studies with samples defined as young adults, although they may have consisted of, for example, 18–65-year-olds, and accordingly determined all

Discussion

The prevalence rates of psychiatric disorders are high among young adults, with depressive and anxiety disorders being among the most prevalent ones. However, research has thus far provided very little information of the neuropsychological profile in affective disorders among young adults with congruently defined age range. Consequently, in the inclusion of studies for the present review, the criteria for sample age were defined relatively wide-ranging.

In this review, findings from single

Role of funding source

This work was supported by The Academy of Finland and the Finnish Graduate School of Psychiatry. Neither had a further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication.

Conflict of interest

All authors declare that they have no conflicts of interest.

Acknowledgements

This work was supported by The Academy of Finland and the Finnish Graduate School of Psychiatry.

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