ABSTRACT
BACKGROUND: Cognitive deficits are common in major depressive disorder, but their nature is unclear. The effort hypothesis states that performance on effortful tasks is disproportionately impaired compared with the performance on automatic tasks. The cognitive speed hypothesis states that depression is characterized by cognitive slowness, which is a source of cognitive dysfunctioning. The present study investigated both theories in unmedicated adult depressive patients. It was also investigated whether the cognitive deficits can be attributed to more general physical illness-related factors or specifically to depressive disorder. METHOD: Thirty non-psychotic depressive out-patients were compared with 38 healthy control subjects and 25 patients with severe allergic rhinitis. The effects of group on more automatic and more effortful aspects of cognitive tasks measuring cognitive speed (Concept Shifting Task, Stroop Colour Word Test, Memory Scanning Test) and memory retrieval (Visual Verbal Learning Task, Verbal Fluency Test) were evaluated by MANCOVA. Age, sex, education and pre-morbid intelligence were treated as covariates. RESULTS: The depressive group had cognitive deficits in the automatic processing subtask of the Stroop, memory scanning and memory span. Performance on more effortful tasks was not impaired. CONCLUSIONS: Our results are more consistent with the cognitive speed hypothesis. Cognitive functioning in depressive disorder seems to be characterized by a reduced speed of information processing in automatic subtasks.
Subject(s)
Cognition Disorders/diagnosis , Depressive Disorder, Major/diagnosis , Neuropsychological Tests/statistics & numerical data , Physical Exertion , Reaction Time , Adult , Age Factors , Attention , Cognition Disorders/psychology , Color Perception , Cross-Sectional Studies , Depressive Disorder, Major/psychology , Discrimination Learning , Female , Humans , Male , Middle Aged , Psychometrics/statistics & numerical data , Reference Values , Reproducibility of Results , Rhinitis, Allergic, Perennial/psychology , Rhinitis, Allergic, Seasonal/psychology , Semantics , Sick Role , Verbal LearningABSTRACT
Few studies have investigated the relationship between cortisol and cognitive functions other than memory in depression. This study investigated daily salivary cortisol patterns (basal cortisol levels at 08:00, 16:00, and 21:00 h and flatness of the diurnal curve) in relation to cognitive speed and memory. Twenty-seven unmedicated outpatients with major depressive disorder (MDD) were compared with 36 healthy controls and with 20 allergic rhinitis patients, to determine whether effects should be ascribed to MDD or to more general disease-related processes. MDD patients were characterised by a flatter diurnal cortisol curve and by reduced cognitive speed. Flatter cortisol curves were associated with cognitive slowness. However, this relationship is unlikely to be causal; after control for depressive symptoms and group membership, flatness of the diurnal cortisol curve was no longer a significant predictor of cognitive slowness. Thus, MDD and related depressive symptoms appeared to be independently associated with altered cortisol secretory patterns and with decrements in cognitive speed.
Subject(s)
Cognition Disorders/metabolism , Depressive Disorder, Major/metabolism , Hydrocortisone/analysis , Rhinitis, Allergic, Seasonal/metabolism , Saliva/chemistry , Adult , Cognition Disorders/diagnosis , Depressive Disorder, Major/diagnosis , Diagnostic and Statistical Manual of Mental Disorders , Female , Humans , Hydrocortisone/metabolism , Male , Neuropsychological Tests , Quality of Life , Severity of Illness Index , Surveys and Questionnaires , Time FactorsABSTRACT
BACKGROUND: Symptomatic allergic rhinitis reduces quality of life as a result of the symptoms experienced and possibly as a result of impaired psychological well-being and cognitive functioning. Few investigations have measured cognitive functions objectively and it remains uncertain whether allergic rhinitis leads to an objective reduction in cognitive functions. OBJECTIVE: To evaluate the relationship between symptomatic allergic rhinitis, cognitive functions and psychological well-being. Differences between subjective and objective cognitive impairments were evaluated. METHODS: The cognitive functions (working memory, memory retrieval, speed of information processing and flexibility of information processing) and psychological well-being of 26 patients with symptomatic allergic rhinitis and 36 healthy controls matched for intelligence, education, age and sex were compared. The influence of education, intelligence, sex and age was considered. RESULTS: Overall, psychological well-being was significantly impaired in the patient group, as shown by higher scores in feelings of insufficiency, complaints of somatization, sleep disturbances and depressive feelings, whereas cognitive function was not. CONCLUSIONS: Allergic rhinitis was related to significantly impaired psychological well-being and to perceived impaired cognitive functioning. However, no significant objective impairment of cognitive functioning was found. Allergic patients may temporarily put more effort into sustaining performance, resulting in earlier exhaustion, which is not noticed during assessment but which impairs psychological well-being.
