Early- and late-onset startle modulation in unipolar depression

In two experimental sessions, we assessed early- and late-onset acoustic startle eyeblink modulation and subjective ratings of emotional pictures by nondepressed participants and by unipolar depressed participants. Depressed participants were assessed before and after treatment with the antidepressant medication Bupropion SR. Both depressed and nondepressed participants exhibited arousal-dependent startle modulation to early probes occurring 300 ms after picture onset. Nondepressed participants demonstrated the expected valence-dependent startle modulation to late probes (3,500-4,500 ms post-onset). In contrast, the late-probe blink magnitudes of depressed patients were unrelated to picture valence. This pattern of group differences was not moderated by treatment. There were no between-group differences in self-report ratings to pictures. These results suggest that depression may be characterized by anomalous responses to affective stimuli and that startle modulation can be a more sensitive index of affective response deficits linked to depression than self-report measures.