Åsa Hammar

Cognitive functioning in major depression--a summary.

The aim of the present paper is to summarize the research during the past decade regarding cognitive functioning in Major Depressive Disorder (MDD). Cognitive impairment in the acute phase of illness has been frequently reported. The findings are shown in different cognitive domains, such as executive functions, attention, memory and psychomotor speed. Fewer reports have investigated cognitive functioning in MDD in longitudinal studies. Some longitudinal reports show that the impairment observed in the acute phase of illness may be long lasting despite symptom reduction and recovery. However, findings regarding cognitive functioning in depression are divergent. Factors that might contribute to the divergent findings, such as depression subtype, severity and comorbidity are discussed. Clinical implications and focus of future research directions is highlighted.In conclusion, depression is associated with cognitive impairment in the acute phase of illness, and some reports indicate that this impairment might be long lasting despite symptom reduction and recovery.

Long-lasting cognitive impairment in unipolar major depression: a 6-month follow-up study

The aim of the study was to investigate cognitive impairment in major depression both acutely and after 6 months. All patients were investigated within a neurocognitive experimental setting at two testing sessions: at inclusion and after 6 months. Automatic and effortful information processing was investigated with a visual search paradigm. Twenty-one patients with recurrent major depression according to DSM-IV and a Hamilton Depression Rating Scale score >18 were included in the study. Healthy subjects, matched for age and gender, were used as a control group. The results showed that the depressed patients performed equal to the control group on trials requiring automatic information processing at both sessions. However, the patients were impaired compared to the control group on trials requiring effortful information processing, also at both sessions. The depressed patients showed no improvement in cognitive performance from test 1 to test 2. The results indicate that the depressed patients had an impaired performance for effortful, but not automatic, visual search performance, and that the impairment remained after 6 months, despite significant improvement in their depression scores.

Brain localization of attentional control in different age groups by combining functional and structural MRI.

The present study used functional and structural MRI to investigate differences in neuronal substrates underlying shifts of attention in young and old subjects, studied with dichotic listening. Two different consonant-vowel syllables were presented and the subjects were instructed to attend to and report from either the left or right ear stimulus. Typically, a right-ear advantage is observed when attending to the right-ear stimulus, and a left-ear advantage when attending to the left-ear stimulus. The behavioral results showed that the old group had difficulties with attentional modulation of the right-ear advantage in the attend left condition. This is interpreted as a failure of an important aspect of attentional control; the top-down biasing of attention for selection of task-relevant stimulus. The fMRI results showed that an area in the left middle frontal gyrus was more activated in the young group compared to the old group in the attend left condition. The structural MRI data showed reduced gray matter density of the same area in the old group. Based on these converging findings, we suggest that the left middle frontal gyrus plays an important role in top-down biasing of selecting task-relevant stimuli, and to inhibit processing of task-irrelevant stimuli. To our knowledge, this is one of the first studies addressing the question on how age-related changes in attentional processing is reflected in both functional and structural differences in the brain.

Selective impairment in effortful information processing in major depression

Automatic and effortful information processing in depressed patients was investigated by a visual search paradigm, in order to examine dysfunctional effortful processing in depressed patients. Twenty-one patients with major depression, according to the DSM-IV, and with a moderate depression measured by the Hamilton Rating Scale score at >18 participated in the study. The healthy control group was matched for age, gender, and level of education. Half of the trials involved only one type of distractor, and the other half of the trials involved two types of distractors being presented. The results show that the performance of the depressed patients was equal to the control group when the target was easily recognized with only one type of distractor present. However, when target detection required a more difficult and complex attentive search strategy, effortful information processing, the depressed patients needed longer visual search time compared to the controls. Depressed patients seem to have impaired performance on effortful but not automatic information processing.

The relationships among heart rate variability, executive functions, and clinical variables in patients with panic disorder.

Heart rate variability (HRV) is reduced in patients who suffer from panic disorder (PD). Reduced HRV is related to hypoactivity in the prefrontal cortex (PFC), which negatively affects executive functioning. The present study assessed the relationships between vagally mediated HRV at baseline and measures of executive functioning in 36 patients with PD. Associations between these physiological and cognitive measures and panic-related variables were also investigated. HRV was measured using HF-power (ms(2)), and executive functions were assessed with the Wisconsin Card Sorting Test (WCST) and the Color-Word Interference Test (CWIT) from the Delis-Kaplan Executive Function System (D-KEFS). Panic-related variables comprised panic frequency, panic-related distress, and duration of PD. Performance on the neuropsychological measures correlated significantly with HRV. Both panic-related distress and duration of PD were inversely related with measures of HRV and cognitive inhibition. The current findings support the purported relationship between HRV and executive functions involving the PFC.

Enduring cognitive dysfunction in unipolar major depression: a test-retest study using the Stroop paradigm.

The aim of the study was to investigate automatic and effortful information processing with the Stroop paradigm in a long term perspective in patients with major depressive disorder (MDD). Patients were tested at two test occasions: at inclusion with a Hamilton Depression Rating Scale (HDRS) score >18, and after 6 months, when most patients had experienced symptom reduction. The Stroop paradigm is considered to measure aspects of attention and executive functioning and consists of three conditions/cards: naming the color of the patches (Color), reading of the color-words (Word) and naming the ink color of color-words (Color-Word). The Color-Word condition is proved to be the most cognitive demanding task and requires the proband to actively suppress interference and is therefore considered to require more effortful information processing, whereas naming the color of the patches and reading the color-words are expected to be more automatic and less cognitive demanding. A homogenous group of 19 patients with unipolar recurrent MDD according to DSM-IV and a HDRS score of >18 were included in the study. A control group was individually matched for age, gender and level of education. Depressed patients performed equal to the control group on the Color and Word cards at both test occasions. However, the patients were impaired compared with the control group on the Color-Word card task at both test occasions. Thus, the depressed patients showed no improvement of effortful attention/executive performance as a function of symptom reduction. The results indicate that the depressed patients showed impaired cognitive performance on cognitive demanding tasks when symptomatic and that this impairment prevailed after 6 months, despite significant improvement in their depressive symptoms.

Test-retest reliability for the consonant-vowel syllables dichotic listening paradigm

The present study compared test-retest reliability for dichotic listening (DL) performance to consonant-vowel (CV) syllables under three different attentional instructions. Previous studies of reliability in dichotic listening have shown great variability which most likely reflects the large variations in stimuli, procedures, and techniques used in the different studies. Sixteen subjects were tested twice, 2 weeks apart, with the same dichotic listening procedure, including a divided attention condition and two focused attention conditions on each test occasion. The results showed test-retest correlations ranging from .61 to .86 for the three attentional conditions, with the smallest correlation coefficient for the divided attention condition.

The significance of personality in pain from gallbladder stones.

Background: The aim of the study was to investigate the association between personality factors related to coping styles and reported pain due to gallstones. Methods: Personality trait measures were completed by 28 consecutive gallstone patients to provide estimates of positive coping resources (Life Regard Index, Sense of Coherence Scale, Sense of Humor Questionnaire) and negative coping resources (Eysenck Personality Questionnaire on Neuroticism, Tension, and Effort Stress Inventory). An overall index of gallstone-related complaints (pain) over the past 7 days/6 months was also obtained. Ultrasonography confirmed the gallstone condition. Multiple regression analyses tested the hypothesis that pain would be moderated by positive coping resources and mediated by negative coping resources. Results: Reported pain was less severe with positive coping resources (39% of pain variance explained) and more severe with negative coping resources (45% of pain variance explained). Conclusion: The results confirm that mental coping resources have a significant role in pain differences among gallstone patients.

Is impairment in cognitive inhibition in the acute phase of major depression irreversible? Results from a 10-year follow-up study

OBJECTIVES Even though many studies demonstrate cognitive impairment in the acute phase of depression and several studies indicate that this impairment might be long lasting despite symptom reduction and recovery, there is a lack of longitudinal studies on this field with considerable follow-up length. The aim of this study was to investigate whether the impairment observed in cognitive inhibition in the acute phase of depression is reversible or irreversible in a 10-year follow-up assessment. DESIGN A longitudinal study of 38 individuals, 19 with recurrent unipolar depression and 19 healthy controls matched for gender, age, and education were included in the study. METHOD Cognitive inhibition was investigated using the Stroop test at three different occasions: acute phase, short-term (6 months), and long-term (10 years) follow-up. RESULTS The results show that recurrent major depressive disorder patients have a long-lasting impairment in inhibition as measured by the Stroop test in 10-year follow-up. Further there is high consistency in inner group performance suggesting that severe impairment in the acute phase of illness is associated with severe impairment 10 years later despite recovery in the patient group. CONCLUSIONS The results show that impairment in cognitive inhibition is long lasting when present in the acute phase of recurrent depression. Impaired cognitive inhibition might be an irreversible vulnerability marker for recurrent depression.

Testing the cognitive effort hypothesis of cognitive impairment in major depression

Background: It is widely accepted that depression is associated with deficits in a range of cognitive domains. However, there is no consensus regarding the neuropsychological profile in depression. Aim: The aim of the present report is to test the cognitive effort hypothesis as a possible framework for understanding the observed cognitive impairment in major depressive disorder (MDD), using the Delis Kaplan Executive Function system (D-KEFS). Method: Twenty-four patients with recurrent MDD, in the acute phase of illness, were compared with a healthy control group. We expected that the patient group would show impairment on tests that measure higher-level effortful cognitive processing, whereas basic cognitive skills would be equal to the control group. Results: There were no differences between the two groups on measures of basic cognitive skills, except for Colour Naming. Furthermore, MDD patients performed significantly worse than the control group on three out of seven of the cognitively effortful measures; namely Inhibition, Inhibition/Switching and Category Fluency. Conclusions: We could not find consistent support for the cognitive effort hypothesis in the present study. However, the results indicate that depressed patients have a specific impairment within the Executive Function domain affecting Inhibition, Inhibition/Switching and Category Fluency.