Seasonal and mood independence of low basal prolactin secretion in premenopausal women with seasonal affective disorder.

To test hypotheses of opposing roles of dopamine and serotonin in prolactin secretion in seasonal affective disorder, the authors determined basal serum prolactin concentrations for premenopausal women, eight with and 14 without seasonal affective disorder, in late afternoon during the follicular phase of the menstrual cycle (and a subgroup during the luteal phase) in winter and summer. Despite their significantly higher Hamilton depression scale scores in winter than in summer, the patients had significantly lower prolactin concentrations than the control subjects in both seasons. These results suggest that low prolactin secretion may be a trait characteristic in seasonal affective disorder.

Modulatory role of serotonin in neural information processing: implications for human psychopathology.

Investigation of the role of 5-hydroxytryptophan (5-HT), which functions as a modulator in the central nervous system, across behavioral contexts suggests that a general principle of transmitter function may be derived that is independent of specific behaviors and specific neural loci. A functional principle of 5-HT action in neural information processing in the central nervous system is proposed. Extremes deviations in 5-HT activity result in biases in information processing that may have direct effects on behavior. Such biases may predispose to pathological conditions such as violent suicide and aggression.

General behavior inventory identification of unipolar and bipolar affective conditions in a nonclinical university population.

Validated the General Behavior Inventory (GBI), revised to identify unipolar as well as bipolar affective conditions, in a nonclinical sample (n = 201) against naive, interview-derived diagnoses. For bipolar and unipolar conditions, respectively, the GBI had high positive (.94, .87) and negative (.99, .93) predictive power with the effect of prevalence considered, adequate sensitivity (.78, .76), high specificity (.99, .99), and adequate selection ratios for sampling of affective and nonaffective subjects from nonclinical populations for research purposes. The utility of the GBI in several different research contexts is discussed.

Dimensional measurement of seasonal variation in mood and behavior.

Recent epidemiologic studies have found that the behaviors that characterize seasonal affective disorder (SAD) show seasonal variation in 92%-95% of the general population, suggesting that seasonal variation in behavior and mood is a continuous, dimensional variable extending throughout the general population, defined at the upper extreme by SAD. Research into population seasonality will require a dimensional measure of seasonal variation in mood and behavior that produces a broad, finely graded distribution of seasonality scores sensitive to individual differences throughout the entire range of scores. Accordingly, the Inventory of Seasonal Variation (ISV) was developed as such a measure. This study demonstrated that the ISV has high internal structural validity and is highly sensitive to individual differences in seasonality across its entire range of scores in the normal population. This latter characteristic is not shared by other existing measures of seasonality. Initial external validity of the ISV was supported in that the mean of ISV scores of a SAD sample was found to lie at the 97th percentile of the normal population of scores. Analysis of ISV scores revealed that a winter pattern of seasonality was reported by over 95% of subjects, a pattern that was more pronounced in women than men, while a summer type of seasonality was reported by only 0.6% of the general population.

Thermoregulatory response to thermal challenge in seasonal affective disorder: a preliminary report.

It has recently been proposed that alterations in central dopamine (DA) functional activity may, in part, account for certain behavioral changes observed in seasonal affective disorder (SAD) during the winter. To explore this possibility, a preliminary study of thermoregulatory heat loss to an endogenous heat challenge--a strongly DA-dependent process--was undertaken in groups of four SAD woman and four nonpsychiatric control women across three conditions (winter, after successful phototherapy, and summer). Homeostatic heat loss during recovery from heat challenge in SAD, but not in control, subjects was found to be a significant function of light condition and of clinical state. Thermoregulatory heat loss in SAD subjects was significantly blunted in winter during depression, was similar in efficiency to control subjects after a successful antidepressant response to phototherapy, and tended to be more efficient than controls in summer during a euthymic state. Results raise the possibility that a common effect of phototherapy and summer light conditions is a facilitation of central DA activity in SAD.

Heat-loss response to a thermal challenge in seasonal affective disorder.

This study extends earlier findings of poorly facilitated postexercise heat loss during the winter in seasonal affective disorder (SAD). While depressed in the winter, 19 SAD subjects exhibited a significantly impaired postexercise heat loss relative to 10 control subjects. During the summer while euthymic, SAD subjects did not significantly differ from control subjects in postexercise heat loss. Since thermoregulatory heat loss is a highly dopamine-dependent process, these results support earlier findings of poorly facilitated dopamine availability in SAD during the winter and suggest a centrally mediated effect of light in SAD.