Personality, brain electrical activity and neuropsychology in medication-free patients with major depression

Although clinical depression is an exhaustively-researched phenomenon, the effect of medication may have compromised many previous studies. Some research shows that medication and its side effects reduce a range of psychological and physiological functioning: unfortunately, the impacts of medication are poorly documented. This doctoral research consisted of three studies of the personality, brain electrical activity and neuropsychology functioning in medication-free clinically depressed patients. As few previous studies used medication-free patients, it was unclear if the data in the present study would be consistent with past research. Based on past research it was hypothesised that clinically depressed patients would score highly on neuroticism and low on extraversion; and that these patients would exhibit left prefrontal hypo-activity when brain electrical activity was recorded; and that they be impaired on cognitive tasks that required high levels of cognitive effort when compared to non-depressed controls. The same of 22 clinically depressed patients were used for all three studies, all of whom were medication-free during their participation and diagnosed as experiencing Major Depression. The “healthy” control group comprised 27 participants without a current diagnosis of any psychiatric illness. Assessment of personality, brain electrical activity and cognitive functioning was conducted using the Revised NEO Personality Inventory, Steady State Visual Evoked Potentials with the International Affective Picture System and Emotional Stroop as activation tasks and a battery of neuropsychological tests (Reaction Time, Choice Reaction Time, Trail Making A and B, Digit Span Forwards and Backwards, Digit symbol and Inspection time) respectively. The results supported hypotheses relating to personality but not for those relating to brain electrical activity or cognitive functioning. Neuroticism was found to be high and extraversion low in the clinically depressed patients. Prefrontal activity was seen during the presentation of depressive words but not when unpleasant images were shown. Impairment in cognitive functioning was limited to tasks which assessed psychomotor functioning. This was interpreted as indicating that medication does not significantly impact on personality assessment. The brain electrical activity measured in the present study differed to that observed in past research on clinical depression, possibly due to the use of an activation task while recording the EEG. The psychomotor deficit may be a core impairment that is present even without medication. The most important inference drawn from the research was that personality, cognitive deficits and brain electrical activity are be related to each other suggesting that cognitive effort may be important in multiple areas.