Epidemiological findings of seasonal changes in mood and behavior. A telephone survey of Montgomery County, Maryland

Seasonality in human sleep

The timing of sleep and sleep EEG parameters in 10 healthy male subjects were investigated in four seasons under controlled conditions. The phase of nocturnal sleep was delayed about one and a half hours in winter as compared to that in summer. The duration of stage 4 sleep decreased and REM sleep increased significantly in winter compared with summer. The seasonality in the timing of sleep can be explained by photoperiodic time cues, but the changes in sleep EEG parameters are difficult to explain in terms of photoperiod.

The Zurich Study. XIV. Epidemiology of seasonal depression

In a longitudinal cohort study of young adults from the Canton of Zurich in Switzerland (Zurich Study), seasonal patterns of several psychiatric and psychosomatic syndromes were investigated in two interviews over a period of three years. At an age of 27-28 years, 23% of the depressives, 15% of the neurasthenic subjects, and 14% of the subjects with backache reported an increased susceptibility in autumn and/or winter. With respect to the course we found that 10.4% of the subjects of the longitudinal sample (n = 417) suffered from seasonal depression (including individuals with subsyndromal seasonal difficulties) over two consecutive years. Specific symptoms, such as hypersomnia, increase of appetite or weight gain, were not found to be consistently associated with seasonal depression. A comparison of actual and retrospective reports on seasonal depression resulted in a very low reliability. In view of these results the seasonal subtype of depression should be diagnosed with caution, except when the diagnosis is based on longitudinal observations and/or external sources of information (e.g. family members, partner).

Recurrent brief depression and its relationship to seasonal affective disorder

Recurrent brief depression (RBD) and seasonal affective disorder (SAD) have been both recently described as subgroups of major depression (DSM-III-R). We have established a relationship between these two syndromes in a cohort of 42 outpatients who presented themselves to a clinic for seasonal affective disorder at the Psychiatric Department of the University of Bonn, FRG. Our preliminary data indicate that 31% of the patients who were diagnosed as suffering from either SAD or its subsyndromal form (S-SAD) can also be categorized as RBD (RBD-seasonal) in a 1-year observation period. During the time span of 1 year RBD-seasonal patients had a mean number of 20 (SD 9) episodes compared with 6 (SD 5) episodes (P less than 0.001) in the group of seasonal patients without BRD. These episodes were accentuated in fall/winter and outnumbered those in spring/summer significantly (P less than 0.001). The mean duration of each episode was 4.6 (SD 2.6) days in the RBD-seasonal group and 21.8 (SD 29) in the non-RBD-seasonal group. Patients with RBD-seasonal experienced seasonal changes as more of a problem and reported a lower percentage of first-degree relatives with a history of depression than the non-RBD-seasonal group.

Contrasts between symptoms of summer depression and winter depression

Epidemiological studies and studies of clinical populations suggest that there are primarily two opposite patterns of seasonally recurring depressions: summer depression and winter depression. In addition, there is preliminary evidence that the two seasonal types of depression may have opposite types of vegetative symptoms. In the present study, we prospectively monitored symptoms of depression in 30 patients with recurrent summer depression and 30 sex-matched patients with recurrent winter depression and compared the symptom profiles of the two groups. Consistent with predictions based on the earlier reports, we found that winter depressives were more likely to have atypical vegetative symptoms, with increased appetite, carbohydrate craving, weight gain and hypersomnia, and that summer depressives were more likely to have endogenous vegetative symptoms, with decreased appetite and insomnia. A cluster analysis performed on the patients' symptom profiles without reference to season of occurrence of their episodes separated 78% of the summer depressives and winter depressives from each other on the basis of their symptoms (chi 2 = 19.29, P less than 0.001).

Seasonal affective disorder in adolescence

Two adolescent girls with seasonal affective disorder (SAD) are described. It is suggested that the classic symptom profile seen in adults is not characteristic in younger subjects. Although hypersomnia is prominent, increased appetite and carbohydrate craving are rarely reported. Local meteorological data link the course of the disorder in one case to the hours of sunshine and ambient temperature during the winter months.

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.

Multiple sclerosis and latitude: a new perspective on an old association

For 68 years latitude has been identified as an important risk factor in the occurrence of multiple sclerosis (MS), but not satisfactory explanation has been offered for this relationship. Epidemiological studies of MS, however, have failed to take into account the degree of change in the amount of ambient light over the course of the year, a variable which is closely related to photoperiod and latitude. Seasonal affective disorder (SAD), another illness for which latitude is a risk factor, appears to be related to the decrease in ambient light during the winter months, and offers some relevant insights into the geographical distribution of risk for developing MS. Researchers have found a relationship between degree of reported seasonal difficulties in a population sample and altered immunological function. Furthermore, the effects of bright light on mood have been shown to be regulated through the eye. We hypothesize that the risk of developing MS is related to impairment of the immune system caused by light deprivation prior to adulthood.

Seasonal mood symptoms in bulimia nervosa and seasonal affective disorder

Mood and appetite disturbances are commonly found in bulimia nervosa and seasonal affective disorder (SAD). To investigate seasonality of mood symptoms, we administered the Seasonal Pattern Assessment Questionnaire (SPAQ) to 38 consecutive bulimic patients, 38 age- and sex-matched SAD patients, and 25 age- and sex-matched normal controls. The SPAQ is a reliable, retrospective, self-rated questionnaire that assesses seasonal changes in mood, sleep, weight, and social activity. The SAD patients had significantly higher Global Seasonality Scores (GSS) than the bulimic patients, who had higher scores than the control group (F = 78.6, df = 2.98, P less than .0001). Forty-two percent of bulimics met case-finding SPAQ criteria for SAD, compared with none of the control group (chi 2 = 14.1, df = 1, P less than .0005). These data suggest that a significant number of unselected bulimic patients have seasonal mood symptoms as severe as that seen in SAD. We propose that a common neurobiologic abnormality, such as serotonergic dysfunction, may underlie the common symptoms found in bulimia and SAD.

Can winter depression be prevented by light treatment?

The administration of light at the development of the first signs of a winter depression appears to prevent it from developing into a full-blown depression. No patient from a group of 10 treated in this way developed any signs of depression during the rest of the winter season, while five of seven patients from a control group became depressed and needed treatment during the winter season.

Seasonal variations in mood and behavior in the general population: a factor-analytic approach

In a mailed survey conducted at four centers--Nashua, NH; New York, NY; Washington, DC; and Sarasota, FL--1,671 respondents provided information on monthly variations in 10 behavioral categories representing extremes in the areas of mood, socializing, appetite, weight gain/loss, and sleep length. A 10-factor solution revealed the following factors: (1) a winter weight gain factor; (2) a winter depression factor; (3) a winter hypersomnia factor; (4) a summer weight gain factor; (5) a summer hypersomnia factor; (6) a summer depression factor; (7) a winter socializing factor; (8) a winter weight loss factor; (9) a fall depression factor; and (10) a possibly mixed factor. Factors consistent with winter seasonal affective disorder were positively correlated with latitude, while those consistent with summer seasonal affective disorder were negatively correlated with latitude.

Mental distress during winter. An epidemiologic study of 7759 adults north of Arctic Circle

The prevalence of mental distress in a general population north of the Arctic Circle at 69 degrees N was studied over 4 midwinter months. Within the framework of a health survey for coronary heart disease, 3 questions about depression, coping problems and insomnia were posed. They were answered by 7759 people randomly assigned to a survey date from November to February. The extreme lack of daylight in December and January taken into consideration, the prevalence of mental distress found, 14% in men and 19% in women, is remarkably low compared with previous epidemiologic research. Except for insomnia in women, which was most prevalent in December, no significant relationship between month of survey and any of the 3 symptoms were found. Thus, the findings cast some doubt upon the importance of daylight for mental distress in the general population.

The temporal onset of individual symptoms in winter depression: differentiating underlying mechanisms

The transition from well to depressed offers a window to the mechanisms which underlie depressive symptoms. We examined the onset of each of 15 symptoms in 53 patients with winter depression. Three symptoms had a risk of onset closely associated with the onset of the episode itself and may represent a core syndrome. The risk of onset for the remaining symptoms was unrelated to the onset and the course of the episode. The symptoms were equally likely to begin at any time during the episode and suggest a different pathological mechanism. A dual vulnerability hypothesis is proposed; research and treatment implications are discussed.

Geophysical variables and behavior: LXV. Seasonal changes in mood in opioid addicts on the Addiction Research Center Inventory

Seasonal changes in mood using the Addiction Research Center Inventory (ARCI) were tested in 243 male opioid addicts when they were free of drug and withdrawal effects. No significant changes were found on scales which measure euphoria (MBG), tension-anxiety (LSD), excitement (Ex), or dysphoric effects (SOW). A significant difference between seasons was found for lowered motivation (PCAG) in the summer and spring relative to winter, but these effects were not consistent with a winter seasonal affective disorder. Significant changes were more common for spring-fall and summer seasons relative to winter on items of the inventory.

Immunological correlates of seasonal fluctuations in mood and behavior and their relationship to phototherapy

Immunological parameters were studied before and after phototherapy, with bright and dim light, in 38 individuals with a range of retrospectively reported seasonal changes in mood and behavior. There was a significant negative correlation between the degree of mood and behavioral difficulties in fall and winter (seasonality) and the total number of circulating natural killer cells. Changes in the numbers of circulating helper T cells correlated significantly with changes in mood following phototherapy. Moreover, mitogen-induced lymphocyte blastogenesis increased significantly after phototherapy, but there was no significant difference between the bright and dim light treatments. The results suggest that cellular immune function is associated with both seasonality and response to phototherapy.

Treatment of seasonal affective disorder with high-intensity light. A phototherapy study with an Icelandic group of patients

The standard phototherapy procedure for seasonal affective disorder (SAD) has been to expose patients to 2500 lux light intensity for 2 h. This study investigated whether high-intensity light treatment with a brief exposure time would relieve symptoms of SAD. Ten SAD patients were randomly assigned to 40-min exposure to 10,000 lux white light or to 400 lux red light which served as placebo. Each patient received treatment for 8 days, and after a wash-out period was crossed over to the other treatment condition. Depression was assessed by the 21-item HDRS and SIGH-SAD by a blind rater and the patients completed the BDI for self-assessment. Significantly greater improvement was found with 10,000 lux treatment than with the placebo (P = 0.011, P = 0.017 and P = 0.028 for SIGH-SAD, HDRS and BDI respectively). The 10,000 lux therapy improved the SIGH-SAD score by an average of 16.1 while the average improvement on placebo treatment was 5.0. The patients were rated again the following summer; most of them were the symptomless. Those patients who improved most on phototherapy also tended to improve most during the summer.

Evaluation of seasonality in six clinical populations and two normal populations

The Seasonal Pattern Assessment Questionnaire (SPAQ) was used to evaluate retrospectively self-reported seasonal changes in mood and behavior (seasonality) of two normal and six clinical populations: patients with winter-seasonal affective disorder (SAD), summer-SAD, eating disorders, bipolar affective disorder, major depressive disorder and subsyndromal winter-SAD. The SPAQ successfully discriminated between groups expected to have high seasonality scores, such as winter-SAD, summer-SAD and subsyndromal winter-SAD, and normal controls. Bipolars and major depressives had normal seasonality scores. Patients with eating disorders had unexpectedly high scores. There was a general tendency for all groups to eat and sleep more and to gain weight in the winter. The implications of these findings are discussed.

Natural summer and winter sunlight exposure patterns in seasonal affective disorder

Twelve subjects with winter depression who lived in the Chicago area recorded their times of going outside during daylight hours for one week during the winter and one week during the summer. These records produced estimates of the duration of daily sunlight exposure and of perceived dawn, dusk and skeleton photoperiod. There was more than twice as much sunlight exposure in summer compared to winter (3.0 vs. 1.2 h/day). The perceived skeleton photoperiod was 4-5 h longer in summer than winter, with a later perceived dusk contributing more to the lengthening than an earlier perceived dawn. The duration of sunlight exposure and perceived skeleton photoperiod in both seasons was much less than what was possible given the available daylight. These results are discussed with reference to the modern urban life style, bright light treatment of winter seasonal affective disorder, and factors which affect the perceived intensity of sunlight.

Seasonality in major depressed inpatients

The proportion of patients with a fall-winter pattern of feeling worst comparable to that of patients with seasonal affective disorder (SAD) was 11.4% in our sample of major depressed inpatients. Since admission to psychiatric inpatient services is influenced to an unknown extent by various factors it is not possible to generalize our data to other facilities. However, based on the results of our study it seems worth while to screen depressed patients for their degree of seasonality since treatment with bright artificial light has been shown to be beneficial in SAD patients and its subsyndromal form.

Prevalence of seasonal affective disorder at four latitudes

The Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to a sample population balanced for sex and randomly selected from local telephone directories in four areas: Nashua, NH, New York, NY, Montgomery County, MD, and Sarasota, FL. On the basis of responses to this questionnaire, prevalence rates of winter seasonal affective disorder (winter SAD), summer seasonal affective disorder (summer SAD), and subsyndromal winter SAD were estimated for the four areas. Rates of winter SAD and subsyndromal SAD were found to be significantly higher at the more northern latitudes, while no correlation was found between latitude and summer SAD. The positive correlation between latitude and prevalence of winter SAD applied predominantly to the age groups over 35.