Seasonal alteration in taste detection and recognition threshold in seasonal affective disorder: The proximate source of carbohydrate craving

Increased appetite with associated carbohydrate craving are core symptoms of seasonal affective disorder (SAD) and have been attributed to decreased central serotonergic function. The proximate mechanisms for centrally mediated selective macronutrient consumption are unknown. We questioned whether seasonal alterations in taste sensation could serve as a mediator of dietary intake, as implied by the term 'craving'. Specifically, individuals who were seasonally depressed and reported carbohydrate craving would be more sensitive to gustatory cues associated with the presence of carbohydrate than nondepressed subjects. Taste detection and recognition thresholds for the four primary gustatory sensations - sweet, sour, salty, and bitter - were obtained in a group of 25 SAD patients and 23 non-psychiatric subjects during the winter, after 2 weeks of 10 000 lux morning and evening light treatment, and during the summer. Relative to the comparison group, the SAD group was less sensitive to sweet taste during the winter. Sweet taste threshold in the SAD group normalized during the summer; however, 2 weeks of light treatment failed to alter sweet detection thresholds in the SAD group. Moreover, within the SAD group, season exerted significant effects on sweet, sour, and bitter detection, but it did not influence salt-detection thresholds. The findings represent the first demonstration of specific changes in taste perception associated with the self-report of carbohydrate craving in SAD and are discussed in terms of the development of sweet craving and the serotonin hypothesis of SAD.