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Title: Effects of major depressive disorder (MDD) on information processing, cognitive and community functioning
Authors: Ahorsu, Daniel Kwasi
Degree: Ph.D.
Issue Date: 2021
Abstract: Background: Major depression disorder (MDD) patients have been reported to have cognitive impairments and especially, psychomotor retardation. However, this assertion was found to be inapplicable during information processing of sad emotional stimuli. This study, therefore, examined "where and why" this is so and also exploring the impact of MDD on participants' cognitive and community functioning. Method: Two different tasks, a choice reaction time task (CRTT) and a hybrid Go/Nogo task (GNG), were used to explore the aim of this cross-sectional chronopsychophysiological study using event-related potential (ERP). Stimulus-response compatibility and foreperiod duration were manipulated so as to affect response choice and motor adjustment/preparation stages. For the first study, 57 participants [19 participants each for first episode MDD (FMDD), recurrent episodes MDD (RMDD) and HCs] were used in the CRTT with and without emotional stimuli. The second study used 50 participants [25 participants each for MDD and HCs] for the GNG with and without emotional stimuli. The participants were also assessed on neuropsychological and psychosocial measures to ascertain their cognitive and community functioning skills.
Result: For the CRTT studies, irrespective of the stimuli, revealed that RMDD outpatients had less accurate scores and impaired controlled processes (P3b Amp) than HCs. However, emotional stimuli affected the results such that HCs had more orientation (N2b Amp) toward happy and neutral emotions than FMDD outpatients, RMDD outpatients had increased motor preparation (CNV Amp) for happy and neutral emotional stimuli than HCs and a change in the organisation of information processing stages between the groups. For GNG studies, non-emotional stimuli only found that HCs had longer stimulus discrimination (N1 latency) but emotional stimuli elicited more significant between-group differences. That is, for happy emotion, MDD outpatients (compared with HCs) had more facilitatory stimulus discrimination (Go N1 amplitude) but less inhibitory stimulus discrimination (Nogo N1 amplitude), deficient conflict monitoring processes (Nogo N2 amplitude) but more conflict resolution and behavioural inhibitory processes (Nogo P3 amplitude) for incompatible condition. For sad emotions, MDD outpatients (compared with HCs) had a longer automatic top-down attention processes (Go N2 latency) for compatible condition but shorter conflict monitoring processes (Nogo N2 latency) for incompatible condition, shorter response activation or conflict resolution and behavioural inhibitory processes (P3 latency) impaired motor preparation (CNV amplitude) and facilitatory motor preparation (Go CNV amplitude) at site Fz. Although both groups used parallel model for processing sad emotion at the late/central processing stage (P3 lat), MDD outpatients were faster than HCs as they used several forms of the parallel model. Both CRTT and GNG studies revealed that depressed outpatients had cognitive challenges and poorer community functioning skills. Discussion and Implication: MDD affected cognitive functioning, community functioning and speed of information processing (especially using emotional stimuli) by either serial or parallel information processing. This implies that MDD outpatients have substantial cognitive and community functioning challenges which may be improved by interventions such as cognitive skills training and social skills training. Also, emotion modulated information processing which suggests that MDD outpatients could benefit from mindfulness-based cognitive and emotive therapy. These novel GNG chronopsychophysiological studies serve as a blueprint for further studies on emotional information processing using other more sophisticated investigative methods such as fMRI. There should also be further studies on the effectiveness of some of the proposed therapeutic interventions in mitigating the MDD challenges observed. Other significant clinical and research implications and recommendations are proffered.
Subjects: Depression, Mental
Hong Kong Polytechnic University -- Dissertations
Pages: xvi, 290 pages : color illustrations
Appears in Collections:Thesis

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