Dr. Young's Lab
Remission of seasonal affective symptomsAnnemarie Reardon, Masters (2003).
Young & Schmitt (2000) reported a change in the course of Seasonal Affective Disorder (SAD) energy symptoms at, or shortly after, the Spring Equinox (March 21; see figure). This phenomenon had not been reported before, possibly because its detection requires daily data. In that study, the number of participants was small (N=10) and participants were limited to individuals diagnosed with SAD. The current study examined the seasonal course of energy/motivation in a larger sample of non-clinical participants.Methods:
Before bedtime each evening, 45 college student participants completed a set of visual analogue scales to assess cognitive, affective, and vegetative features related to seasonality. Studies have found such scales to be reliable and valid measures of change over time of depressive symptoms. The energy/motivation factor has been confirmed in studies of SAD and nonclinical samples. Data were collected for 41-73 days beginning between February 22 and March 5 and ending between April 21 and May 9. None of the participants were taking psychotropic medications or using light treatment at the time of the study. Multiphase regression analysis (Cudeck & Klebe, 2002) was used (1) to assess whether the number of phases in the course of energy/motivation and (2) to assign a date for the change point between phases.
For 20 of the 45 participants, a two-phase course was observed (see figure). Change points were distributed fairly normally around a point several days after the Spring Equinox (median, March 26.5; range, March 2 to April 20). Of the remaining 25 participants, 19 exhibited a single-phase course (increasing or decreasing), 3 exhibited stable levels of energy/motivation, and 3 exhibited more complex, multiphase patterns.
A change in the course of energy/motivation now has been observed in clinical and non-clinical samples and in two different calendar years. Explanations of this finding are speculative. We can identify no psychosocial events to account for the findings. At the Spring Equinox, the length of day and night are equal, the rate of change in photoperiod (first derivative) changes from positive to negative, and the acceleration (second derivative) in photoperiod is zero. A possible explanation of the results is that either (a) the difference in length of day and night or (b) the daily acceleration in photoperiod serves as a signal to the organism. Shortly before and after the Equinox, the magnitude of both these signals is close to zero. In the absence of a signal, the regulation of the energy/motivation system may become weak; with reestablishment of the signal following the equinox, regulation of energy/motivation is reestablished but with a new trajectory.