'Cognitive inflexibility', evidenced by impaired set-shifting and inhibitory control, is a well established feature of acute depression. The extent to which inflexibility is a 'state' characteristic, present only during active depression, or an underlying 'trait' vulnerability that precedes the disorder's emergence and increases risk of onset, relapse and recurrence, is however uncertain. Clarification of its status as a potential risk marker is an important research and clinical objective in the development of early detection, intervention and prevention strategies. The first paper is a systematic methodological review of recent studies investigating set-shifting and inhibitory control in remitted depression and at-risk samples. While some studies report deficits in remission and in at-risk twins, the findings overall are inconsistent and are confounded by methodological limitations in terms of neuropsychological test administration and sample matching and heterogeneity. Given the paucity of at-risk investigations, the findings do not provide a convincing body of support for either 'cognitive scars' that persist in remission, or underlying vulnerabilities, nor do they clarify the state-trait debate. Further research in at-risk populations is recommended, but methodologically improved and more consistent study design and test selection is essential. The second paper investigated whether cognitive inflexibility and attentional bias for negatively valenced information, as candidate disorder risk factors, might be observed in never depressed 16-20 year old offspring at genetic risk of depression, but not controls. No differences between groups were observed in terms of set-shifting or inhibition of prepotent responding in relation to neutral stimuli, or of biased attentional orientation. Evidence was, however, observed of inefficient inhibitory control of attention and responses to negatively valenced stimuli in at risk participants, consistent with the possibility that deficits in affective inhibitory control are vulnerability candidates. Implications of the findings, together with study limitations and recommendations for future research are considered.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:589524 |
| Date | January 2012 |
| Creators | Preston, Ciara |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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