Relationship between cognitive sensitivity to (symbolic) light in remitted seasonal affective disorder patients and the onset time of a subsequent depressive episode

The role of cognitive sensitivity to light in the development of seasonal affective disorder (SAD, winter type) was studied by comparing 29 SAD patients during remission with 29 non-depressed controls matched by sex and age, and by relating measures for cognitive sensitivity of remitted SAD patients to the onset of a depressive episode during the following autumn/winter. To ensure that only cognitive processes were involved, the subjects were exposed to symbolic light. Thr;ee schematic drawings of ambiguous faces expressing different emotions were embedded in light or dark backgrounds for tl;is purpose. The subjects rated the various facial expressions with respect to the degree of elation-sadness, rejection-invitation, and activation-sleepiness. SAD patients saw larger differences in activation between faces embedded in light and dark backgrounds than controls, perceiving less activation in faces with dark backgrounds. Furthermore, the larger the difference that SAD patients saw in invitation between faces with light and dark backgrounds, the earlier they became depressed in the subsequent autumn/winter. Only the SAD patients who became depressed early (before December 21) differed from controls in the perception of invitation. Results are interpreted within the framework of psychological theories on the development of depression and suggest that altered cognitive sensitivity of SAD patients to light plays a role in the development of depressive episodes.