Attention deficit in depressed suicide attempters

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Abstract

Attention is typically impaired in depression and may play a role in risk for suicidal behavior. In this study, 66 non-patients, 83 depressed subjects with no past history of suicide attempt, 53 depressed subjects with one or more low lethality suicide attempts, and 42 depressed subjects with at least one high lethality attempt were compared on two computerized measures of attention, a continuous performance test (CPT) and a Stroop task. All subjects were medication free at the time of assessment. Attention was impaired in all depressed subjects but worse in those with a past history of suicidal behavior. CPT performance did not differ among the groups, but Stroop interference was significantly poorer in all depressed subjects relative to non-patients, and poorer still in high lethality suicide attempters relative to all other groups. Interference scores correlated modestly with subjective depression, functional level, suicide ideation, number of past suicide attempts, and lethality of past attempts. Depression-related impairments of attention, especially susceptibility to interference, are accentuated in those with a past history of suicidal behavior. Fundamental deficits in attentional control may play a role in risk for suicidal behavior, and may contribute to a variety of cognitive deficits in suicidal patients. Brain regions subserving attentional control, which overlap considerably with regions implicated in affective disorders, may be a useful target for studies seeking to characterize neuropsychological factors associated with suicidal behavior.

Introduction

Attentional deficits are common in major depression (Cornblatt et al., 1989, Lemelin et al., 1996, Lemelin et al., 1997, Thomas et al., 1997, Lemelin and Baruch, 1998, Cohen et al., 2001, Koetsier et al., 2002, Liu et al., 2002, Ottowitz et al., 2002, Den Hartog et al., 2003, Egeland et al., 2003, Siegle et al., 2004), and may also be associated with risk for suicidal behavior. Using a continuous performance task (CPT), Horesh (2001) found higher rates of both omission and commission errors in adolescent suicide attempters compared with hospitalized non-attempters. Tarter et al. (2004) included performance on a vigilance task and a Stroop task in a composite measure of behavioral disinhibition that predicted risk for later substance use and suicide attempt in adolescents. Becker et al. (1999) found greater attentional interference in past suicide attempters than in healthy controls on a Stroop task using suicide-related words as distractors. Our own previous work (Keilp et al., 2001) found that Stroop interference — using standard color/word stimuli in a single item, computerized format — differed significantly between depressed, high lethality past attempters and non-patients, with depressed non-attempters and less lethal attempters intermediate between these two groups. Deficits on the conflict condition of the Attention Network Test were found in patients with Borderline Personality Disorder, a disorder where risk for suicidal behavior is high (Posner et al., 2002). Impairments of attention, then, appear to be common in populations at risk for suicidal behavior, although their nature is not completely clear. Previous results suggest attention may be affected globally; our own data suggest that performance on interference-type tasks may be more closely related to suicide attempt risk. Problems with the executive control of attention may be associated with risk for more severe attempts as well (Nasser and Overholzer, 1999, Keilp et al., 2001).

Other cognitive functions have been linked to suicidal behavior, including poor language fluency (Bartfai et al., 1990), memory disturbance (Williams et al., 1996), problem solving (Pollock and Williams, 1998, Marzuk et al., 2005), decision-making (Jollant et al., 2006), and impulsiveness (Swann et al., 2005). There is little consistency across studies, however, and there are marked differences in sample sizes, nature of comparison groups and composition of test batteries. Attentional disturbance is a common finding across studies that measure it adequately, and may play a role in other higher order cognitive dysfunctions. As a first step in understanding the role of cognitive factors in suicidal behavior, it is reasonable to examine fundamental cognitive capacities such as attention, in as much detail and in samples as large as possible, to determine if or how they might be related to suicidal behavior — before invoking higher order cognitive constructs in these hypothetical models.

In the study reported here, performance data on the same attentional tasks used in our initial study were examined in a significantly enlarged version (178 depressed patients; 66 non-patients) of our original sample (50 depressed patient; 22 non-patients). Tasks included a computerized CPT using four-digit number strings as stimuli, and a computerized Stroop task using single-item presentation of color names and colors. These tasks are common elements in various batteries that have been employed in our center over a decade. The CPT and Stroop tasks are well-established paradigms that assess overlapping but complementary aspects of attention (Posner and Petersen, 1990, Mirsky et al., 1991, Parasuraman et al., 1998) that are typically impaired in psychiatric disease. Deficits on both types of task have been reported in major depression as well as in suicide attempters, as noted above. It is unclear, though, how well these tasks distinguish past attempters from comparably depressed subjects with no past history of attempts. Based on our own previous work and on the published literature, we hypothesized that past suicide attempters would perform more poorly on both. We also sought to determine if either one of these tasks was more sensitive to such deficits. Both CPT and Stroop tasks have been used extensively in functional imaging paradigms (i.e. Perlstein et al., 2003, Wagner et al., 2006), much is known about their neural circuitry (Posner and DiGirolamo, 1998, Cohen et al., 2004), and either could easily be adapted to examine attentional systems in suicidal populations.

Section snippets

Subjects

Subjects were 178 patients meeting DSM-IV criteria for a current Major Depressive Episode, and 66 non-patient comparison subjects. All patients were currently depressed, had a Hamilton Rating Scale for Depression (HRSD, 24-item) score > 16 at the time of recruitment, did not meet criteria for psychotic depression (4.5% had a past history of psychotic symptoms), and had no current substance abuse or dependence (past history of abuse/dependence was present in 36.8% of patient subjects).

Demographic and clinical measures

Subject groups were comparable in education and estimated intellectual level (Table 1). Low lethality past attempters were younger than non-attempters, more likely to be female than non-attempters and non-patients, and more likely to have Borderline Personality Disorder than other depressed patient groups. Percentage of unipolar and bipolar depressed subjects was comparable among patient groups. Overall severity and chronicity of depression were also comparable among patient groups, although

Discussion

Deficits in attention were apparent in all depressed subjects, but significantly greater in past suicide attempters and primarily attributable to their greater susceptibility to interference on the Stroop. In our previous study with a much smaller sample (Keilp et al., 2001), Stroop performance was poor in past suicide attempters, but only distinguished them from non-patients. Increased statistical power in this study enabled us to demonstrate that this impairment in attention is worse in those

Acknowledgements

This study was supported by the National Institute of Mental Health grants MH-062185 and MH-062155, the National Alliance for Research on Schizophrenia and Depression (NARSAD), and the American Foundation for Suicide Prevention (AFSP).

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