Inhibitory deficits for negative information in persons with major depressive disorder.
BACKGROUND
Within Beck's cognitive model of depression, little is known about the mechanism(s) by which activated self-schemas result in the production of negative thoughts. Recent research has demonstrated that inhibitory dysfunction is present in depression, and this deficit is likely valence-specific. However, whether valence-specific inhibitory deficits are associated with increased negative cognition and whether such deficits are specific to depression per se remains unexamined. The authors posit the theory that inhibitory dysfunction may influence the degree to which activated self-schemas result in the production of depressive cognition.


METHODS
Individuals with major depressive disorder (MDD, n=43) versus healthy (n=36) and non-depressed anxious (n=32) controls were assessed on the Prose Distraction Task (PDT), a measure of cognitive inhibition, and the Stop-Signal Task (SST), a measure of motor response inhibition. These two tasks were modified in order to present emotionally valenced semantic stimuli (i.e. negative, neutral, positive).


RESULTS
Participants with MDD demonstrated performance impairments on the PDT, which were most pronounced for negatively valenced adjectives, relative to both control groups. Moreover, these impairments correlated with self-report measures of negative thinking and rumination. Conversely, the performance of the MDD participants did not differ from either control group on the SST.


CONCLUSIONS
Implications of these findings for understanding the mechanisms underlying the development and maintenance of depressive cognition are discussed.
Lau
Mark A
MA
Center for Addiction and Mental Health, Toronto, Ontario, Canada. mlau4@bcmhs.bc.ca
Christensen
Bruce K
BK
Hawley
Lance L
LL
Gemar
Michael S
MS
Segal
Zindel V
ZV
D000328:Adult; D000368:Aged; D001008:Anxiety Disorders / Q000175:diagnosis / Q000523:psychology; D001288:Attention; D003072:Cognition Disorders / Q000175:diagnosis* / Q000523:psychology; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000523:psychology; D004644:Emotions; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D007389:Internal-External Control; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D011930:Reaction Time; D011932:Reading; D012649:Self Concept; D012660:Semantics; D013850:Thinking