Depression is a serious psychological condition and a leading cause of global disability. Research indicates that it is associated with considerable neuropsychological impairment which is thought to play a role in the development, maintenance and recurrence of the disorder. Metacognitive Therapy (MCT) is an emerging psychotherapy and unlike Cognitive Behavioural Therapy (CBT), it incorporates strategies that are aimed at targeting aberrant neuropsychological processes. The aim of this thesis was to compare changes in neuropsychological function in outpatients with depression receiving MCT or CBT and to compare early changes in brain activation within a subgroup of participants.
Forty-eight participants referred for outpatient treatment were randomly assigned to receive 12 weeks of MCT (n=23) or CBT (n=25). Depression severity, rumination and neuropsychological function were assessed pre-treatment, four weeks into treatment and at end-treatment (12 weeks). Nineteen participants from the cohort were also recruited to undergo ASL and BOLD fMRI. Resting state perfusion and brain activation during an emotional processing task were assessed at baseline alongside a group of controls (n=13), and following four weeks of therapy.
No significant differences in neuropsychological task performance were found between the two therapy groups at baseline or at four weeks. At end-treatment, the MCT group showed significantly greater improvement on an executive function task compared to the CBT group. There was also a trend for greater improvement on an attention task in patients receiving MCT. Executive function/attention changes were independent of changes in mood and rumination.
At baseline, the depressed and control groups showed no differences in resting state perfusion, however the depressed group did show greater activation within frontal areas during the processing of genuine sad facial displays in comparison to controls. Following four weeks of treatment, the depressed group showed no differences in resting state perfusion, compared with baseline, but did exhibit decreased activation within parietal, temporal and occipital regions during the processing of genuine sad facial expressions. Baseline activity differences and small numbers in each therapy group precluded the group by time comparison. This novel paradigm is interesting since compared with previously used emotional activation paradigms, it appears to tap different emotion processing circuits, activating prefrontal rather than limbic areas.
Of particular clinical interest, the results suggested that MCT may have a particular benefit in improving aspects of executive function/attention over CBT. This may relate to its purported mechanism of action and address an important clinical feature of depression which is cognitive impairment.
