Cross-regional survey of seasonal affective disorders in adults and high-school students in Japan

BACKGROUND: In Asian countries, there is no epidemiological report on seasonal affective disorder (SAD) in different age groups and different geographic regions surveyed at the same time. The aim of this study was to estimate the prevalence rates of SAD and risk factors for SAD in adults and high-school students, with special reference to the difference of winter SAD between northern and southern regions in Japan. METHODS: A total of 3237 high-school students and 4858 workers living in Japan (31.3-43.5 degrees N) responded to this epidemiological survey using Japanese version of the Seasonal Pattern Assessment Questionnaire (SPAQ). RESULTS: The overall prevalence rates of winter SAD (subsyndromal winter SAD) and summer SAD (subsyndromal summer SAD) in high-school students were 0.91(2.21) and 0.81(2.57)%, respectively. In workers, these rates were 0.45(1.16) and 0.43(0.71)%, respectively. Although no regional difference was noted in high-school students with winter seasonal type, the estimated odds ratio of this type for northern workers was nearly 3-fold higher than the southern counterparts. The prevalence rates of each seasonal type were not significantly different between two sexes in both age groups. No clear dependence on latitude was seen with regard to summer SAD in both age groups. LIMITATIONS: The effect of climate on SAD could not be entirely excluded from geophysical factor as indexed by latitude. CONCLUSIONS: SAD was less common in adults than in high-school students. While latitude was a major determinant of winter type in adults, socio-cultural factors or other contributing factors might affect the development of this type in high-school students.     

Personality of seasonal affective disorder analyzed by Tri-dimensional Personality Questionnaire

BACKGROUND: Although there have been numerous reports in personality of mood disorders, there have been few reports in regard with personality of winter seasonal affective disorder (SAD). Furthermore, no reports have been published concerning summer SAD personality characteristics. Thus, this study was conducted to assess the personality of winter and summer SAD using Tri-dimensional Personality Questionnaire (TPQ) that have been used in a variety of mental disorders. METHODS: A total of 6135 Japanese were evaluated with TPQ, the Seasonal Pattern Assessment Questionnaire (SPAQ) and the Self-rating Depression Scale (SDS). Winter, summer and non-SAD groups were classified by SPAQ. We compared the difference of personality trait among these three groups in consideration of gender, age and SDS score influence. RESULTS: Winter SAD demonstrated higher "Novelty Seeking" and "Harm Avoidance"; summer SAD showed higher "Harm Avoidance" than the non-SAD group. "Harm Avoidance" in both SAD groups was re-analyzed using SDS score as a covariate, and "Novelty Seeking" in winter SAD using age as a covariate. As a result, the significance of high "Novelty Seeking" and high "Harm Avoidance" in winter SAD was excluded. However, "Harm Avoidance" remained the significant difference between summer and non-SAD. LIMITATION: SAD was diagnosed only by SPAQ and not by interview. The state-dependency of "Harm Avoidance" was not confirmed in identical patients over lapse of time. CONCLUSION: Patients with winter SAD have high "Harm Avoidance" dependent on the depressive state that is in accordance with non-seasonal depression. Patients with summer SAD have high "Harm Avoidance" possibly independent from the depressive state.     

Seasonal variations in mood and behaviour: epidemiological findings in the north tropics.

BACKGROUND: There has been no epidemiological study of seasonal affective disorder (SAD) in the north tropics. METHODS: The investigators randomly mailed the Seasonal Pattern Assessment Questionnaire (SPAQ) to 520 residents in Chiang Mai Municipality. RESULTS: The prevalence rates of summer SAD, subsyndromal summer SAD and winter SAD are 6.19%, 8.25% and 1.03%, respectively. CONCLUSIONS: The epidemiological study of SAD in the north tropics finds a high prevalence of summer SAD, low prevalence of winter SAD and the correlation between 'feel worst' response and temperature. LIMITATIONS: The reliability and validity of SPAQ in diagnosing summer SAD is probably low. The response rate from the studied sample is low. CLINICAL RELEVANCE: The prevalence of summer SAD in the tropics is much higher than that in the temperate zone and may relate to temperature.     

A comparison of open treatment of seasonal major and minor depression with light therapy

BACKGROUND: Although several investigators have described a milder form of seasonal affective disorder (SAD), called subsyndromal SAD, little is known about the effect of light therapy in this group. The current study evaluates 3 weeks of open treatment with light therapy in SAD and subsyndromal SAD patients. METHODS: Subjects with major or minor depression according to DSM-IV with a seasonal pattern were recruited during the winter of 1998-1999 from clinic patients and media advertising. Subjects were commenced on open treatment of morning light therapy, for 30 min daily using a new fluorescent light therapy unit that produced approximately 5,000 lux at a distance of 12 inches. The treatment lasted 3 weeks and at the end of the first and second week of treatment the duration of exposure could be increased to a maximum of 60 min at the discretion of the clinician. The Structured Interview Guide for the Hamilton Depression Rating Scale-SAD version (SIGH-SAD) was administered weekly to evaluate outcome. Response was defined in a variety of ways to reflect the fact that subsyndromal SAD subjects had milder symptoms. RESULTS: Forty-six subjects entered treatment and 44 (SAD, n = 29, subsyndromal SAD, n = 15) completed at least 2 weeks. Response rates were generally similar in SAD subjects (64-69%) and subsyndromal SAD (40-67%) patients. There was a trend for longer exposure to be associated with better outcome. CONCLUSIONS: Light therapy may be an effective treatment for subjects with both major and minor depression with a seasonal pattern. Optimal duration, for the light therapy unit used in this study, is likely 45-60 min daily.     

Prevalence of seasonal affective disorder in primary care; a comparison of the seasonal health questionnaire and the seasonal pattern assessment questionnaire

BACKGROUND: Prevalence rates of SAD suggested by previous studies have ranged from 1 to 12% depending on the diagnostic criteria used. The Seasonal Pattern Assessment Questionnaire (SPAQ), a widely used screening tool, has been shown to have low specificity for SAD. The Seasonal Health Questionnaire (SHQ) was designed to better reflect the clinical criteria for SAD and has been shown to have a higher specificity then the SPAQ in a psychiatric outpatient setting. OBJECTIVE: The current study was designed to assess the validity of the SHQ in general practice against systematic research interviews, to compare the sensitivity, specificity and positive predictive values of the SHQ and the SPAQ and to use these data to estimate the prevalence of SAD in primary care. METHODS: 809 subjects in a consecutive series of patients attending Southampton general practices in winter 2000/01 completed the SHQ followed by the SPAQ; 56 were interviewed using the Structured Clinical Interview for DSM (SCID). RESULTS: The SHQ was more sensitive and specific than the SPAQ and had higher positive and negative predictive values in screening for SAD. The SPAQ indicated a prevalence of SAD of 10.7% (95% CI 8.6-13.1) while the SHQ provided a significantly lower estimate of 5.6% (95% CI 4.2-7.4).     

Validation of the Seasonal Pattern Assessment Questionnaire (SPAQ)

The validity of the Seasonal Pattern Assessment Questionnaire (SPAQ) was examined by interviewing 81 individuals who had participated in an earlier community survey of seasonal affective disorder (SAD) in Iceland. When SAD and subsyndromal SAD (S-SAD) were combined into a ‘winter problem’ group, the questionnaire's sensitivity, specificity and positive predictive value for that group were 94%, 73% and 45%, respectively. The SPAQ discriminated poorly between SAD and S-SAD, and hence it had a poor case-finding ability for SAD. Clinical evaluation verified a diagnosis of SAD in individuals who had no previous information about this syndrome. The questionnaire furthermore identified a group of individuals who had generalized anxiety and marked seasonal variations. Clinical evaluation arrived at a similar prevalence rate of SAD as the questionnaire.     

Mood-worsening with high-pollen-counts and seasonality: a preliminary report

BACKGROUND: Because aeroallergens produce inflammation in the respiratory airways, and inflammation triggers depression in vulnerable individuals, we hypothesized that mood sensitivity to pollen, the most seasonal aeroallergen, will be associated with a greater seasonality of mood. Since pollen is absent during winter, we specifically predicted that mood sensitivity to tree pollen will predict non-winter SAD but not winter SAD. METHODS: A convenience sample of African and African American college students who lived in the Washington DC metropolitan area for at least the past 3 years completed the Seasonal Pattern Assessment Questionnaire (SPAQ), from which the Global Seasonality Score (GSS) was calculated, a diagnosis of cumulative SAD (syndromal or subsyndromal SAD) was derived, a seasonal pattern (winter vs non-winter) identified, and self-reported mood changes during high pollen counts obtained. A Mann-Whitney test was used to compare GSS between participants with vs without mood worsening during high pollen counts. The capability of mood worsening with high pollen counts, gender, ethnicity, and age to predict non-winter SAD was analyzed with logistic regressions. RESULTS: GSS was greater (z=5.232, p<0.001) in those who reported mood worsening with high pollen counts. Mood sensitivity to pollen predicted non-winter SAD (p=0.017), but not winter SAD. LIMITATIONS: The SPAQ is not a definitive tool to assess seasonality, and self-reported mood worsening with high pollen counts relies on recollection. No direct measures of depression scores or pollen counts were collected. The non-winter SAD concept has not been previously established. CONCLUSIONS: Our study, which should be considered preliminary in light of its limitations, suggests that self-reported mood-worsening with high pollen count is associated with a greater seasonality of mood, and predicts SAD of non-winter type.     

Seasonal affective disorder in eight groups in Turkey: a cross-national perspective

OBJECTIVE: Previous estimates of the prevalence of seasonal affective disorder (SAD) in community-based samples generally originated from western countries. We report prevalence rates in eight groups from four latitudes in Turkey. METHOD: Seasonal Pattern Assessment Questionnaire (SPAQ) was distributed to the community-based samples from eight different locations at four latitudes in Turkey. The prevalence rates of winter SAD and subsyndromal SAD (S-SAD) were estimated for the four groups at the same latitudes by using SPAQ responses. RESULTS: We distributed 3229 SPAQs, had an overall response rate of 54.16% and 1749 SPAQs were included in the analyses. Seasonality was reported as a problem by 549 subjects (31.57%) of our 1749 respondents. Prevalence of winter SAD and S-SAD are estimated as 4.86 and 8.35%, respectively, for the whole group. Prevalence rates were determined for each center and for four latitudes (two centers at the same latitude were grouped as one). In Adana-Gaziantep (lt. 37), Izmir-Elazi? (lt. 38), Eski?ehir-Ankara (lt. 39) and Trabzon-Edirne (lt. 41), the prevalence rates for winter SAD were 6.66, 2.25, 8.00 and 3.76%, respectively. CONCLUSIONS: Our prevalence estimates of winter SAD are similar to those found in previous community-based studies at the same latitudes; no correlation was found between latitude and prevalence of winter SAD, which could be related to the sampling methodology or to the fact that there were only 5 degrees of difference between the latitudes.     

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.     

Comparison of consultation rates in primary care attenders with and without seasonal affective disorder

BACKGROUND: There is a lack of published information about the consultation patterns of patients with seasonal affective disorder (SAD) in primary care, when compared with non-seasonal controls (NSCs). METHODS: Interview-confirmed SAD cases (n=90) were age- and sex-matched to two controls without significant seasonal morbidity on the Seasonal Pattern Assessment Questionnaire (SPAQ) (non-seasonal controls, NSCs). A comparison of their consultation rates was made using data abstracted from primary care records over 4 years. RESULTS: The monthly rate of general practice consultations for SAD cases was significantly higher than that for NSCs. There was a significant difference in the median number of consultations in winter and autumn between the two groups. The matched multivariate analysis revealed that February and April were the independent months in which cases of SAD had significantly more consultations than NSCs. LIMITATIONS: Optimal diagnostic criteria for SAD have not been determined and our criteria may have been over-inclusive. CONCLUSION: In addition to a marked difference in monthly consultation rates between SAD cases and NSCs, the data demonstrate a difference in the pattern of seasonality of these rates. It is possible that increased frequency of consultation, in particular during the winter months (in patients who score as a case SPAQ), could be used as an indication of SAD in primary care.     

Seasonal affective disorder and social deprivation in Aberdeen

Background: Unlike non-seasonal depression, there is some evidence that seasonal affective disorder (SAD) is more common among more affluent socioeconomic groups. Methods: In primary care settings in Aberdeen, 4557 subjects had previously completed a Seasonal Pattern Assessment Questionnaire (SPAQ). From the subjects’ postcodes they were allocated a Carstairs score which placed them in one of seven categories of socioeconomic deprivation. These categories were compared with regard to seasonal pathology from the SPAQ ratings. Results: Complete postcodes and Carstairs scores were established for 3772 (83%) of the 4557 subjects. No statistically significant relationship between socioeconomic deprivation and SPAQ ratings was detected. Limitations: The study population was an affluent one relative to Scotland as a whole which may have reduced the likelihood of a positive finding. The study was conducted 7 years after the census on which postcode deprivation scores were calculated, and changes therein may have occurred. Conclusions: SAD either has no relationship to social deprivation or is associated with affluence and this distinguishes it from non-seasonal depression.     

A possible association between the Val158Met polymorphism of the catechol-O-methyl transferase gene and the personality trait of harm avoidance in Japanese healthy subjects

Catechol-O-methyltransferase (COMT) is an enzyme that degrades various biogenic amines, which have been hypothesized to be associated with personality traits. We investigated a possible relationship between the COMT Val158Met polymorphism and personality traits assessed by the Temperament and Character Inventory (TCI) in 139 healthy subjects in a Japanese population. The number of Met alleles of the COMT Val/Met genotype tended to relate to harm avoidance (HA) scores parametrically, while no significant difference was observed between genotype groups in either novelty seeking, reward dependence, persistence, self-directedness, cooperativeness or self-transcendence. These results suggest that the Val/Met polymorphism of the COMT gene may play a role in HA in Japanese population.     

The Seasonal Health Questionnaire: a preliminary validation of a new instrument to screen for seasonal affective disorder

BACKGROUND: The main screening tool for Seasonal Affective Disorder (SAD) is the Seasonal Pattern Assessment Questionnaire, but its reliability and validity have been thrown into doubt by several studies. METHOD: In this study we developed a new questionnaire, the Seasonal Health Questionnaire (SHQ), which is scored by computer to derive the four main operational criteria for diagnosis of SAD. A group of clinically diagnosed SAD patients was contrasted with a group of patients with recurrent non-seasonal depressive disorder using the SPAQ and the SHQ. RESULTS: The SHQ could be completed without difficulty by patients with long histories of recurrent mood disorder. The SPAQ and the Rosenthal Criteria were the least specific of the criteria for identifying SAD - misclassifying many non-seasonal patients. CONCLUSIONS: After further development the SHQ may be a more appropriate screening instrument for SAD. The SPAQ should no longer be used for this purpose as it gives misleadingly high estimates of prevalence.     

Dates of birth and seasonal changes in well-being among 4904 subjects completing the seasonal pattern assessment questionnaire

BACKGROUND: Abnormal distributions of birthdates, suggesting intrauterine aetiological factors, have been found in several psychiatric disorders, including one study of out-patients with Seasonal Affective Disorder (S.A.D.). We investigated birthdate distribution in relation to seasonal changes in well-being among a cohort who had completed the Seasonal Pattern Assessment Questionnaire (SPAQ). METHOD: A sample of 4904 subjects, aged 16 to 64, completed the SPAQ. 476 were cases of S.A.D. on the SPAQ and 580 were cases of sub-syndromal S.A.D. (S-S.A.D.). 92 were interview confirmed cases of S.A.D. Months and dates of birth were compared between S.A.D. cases and all others, between S.A.D. and S-S.A.D. cases combined and all others, and between interview confirmed cases and all others. Seasonality, as measured through seasonal fluctuations in well-being on the Global Seasonality Scores (GSS) of the SPAQ, was compared for all subjects by month and season of birth. RESULTS: There was no evidence of an atypical pattern of birthdates for subjects fulfilling criteria for S.A.D., for the combined S.A.D./S-S.A.D. group or for interview confirmed cases. There was also no relationship between seasonality on the GSS and month or season of birth. LIMITATIONS: Diagnoses of S.A.D. made by SPAQ criteria are likely to be overinclusive. CONCLUSION: Our findings differ from studies of patients with more severe mood disorders, including psychiatric out-patients with S.A.D. The lack of association between seasonality and birthdates in our study adds credence to the view that the aetiology of S.A.D. relates to separable factors predisposing to affective disorders and to seasonality.     

Personality and seasonal affective disorder: results from the CAN-SAD study

BACKGROUND: Personality factors have been implicated in seasonal affective disorder (SAD). The present study investigated the relationship between the five-factor model of personality (neuroticism, extraversion, openness, agreeableness, conscientiousness) and SAD. METHODS: Ninety-five patients with SAD completed personality measures before and after treatment in a clinical trial and during the summer months. The personality scores of the SAD patients were compared with a matched group of non-seasonal depressed patients and published normative data. Stability and change in personality scores with changes in mood state were assessed. Personality dimensions were evaluated as possible predictors of treatment outcome. RESULTS: SAD patients showed elevated openness scores relative to both non-seasonal depressed patients and norms. Their neuroticism scores were lower than non-seasonal depressed patients, but higher than norms. All personality dimensions showed large and highly significant test-retest correlations but several personality dimensions, particularly neuroticism and extraversion, also showed considerable change with changing mood state. None of the personality dimensions were significantly associated with treatment outcome. LIMITATIONS: Personality assessment relied on self-report. CONCLUSIONS: The personality profile of SAD patients differs from both non-seasonal depressed patients and norms. Elevated openness scores appear to be a unique feature of patients with SAD. Since mood state has a significant impact on personality scores, assessment of personality in SAD patients should ideally be conducted when they are in remission. Further investigation of the relationship between personality and SAD, especially the potential significance of elevated openness scores, is warranted.     

Heritability and linkage analysis of personality in bipolar disorder

Background

The many attempts that have been made to identify genes for bipolar disorder (BD) have met with limited success, which may reflect an inadequacy of diagnosis as an informative and biologically relevant phenotype for genetic studies. Here we have explored aspects of personality as quantitative phenotypes for bipolar disorder through the use of the Temperament and Character Inventory (TCI), which assesses personality in seven dimensions. Four temperament dimensions are assessed: novelty seeking (NS), harm avoidance (HA), reward dependence (RD), and persistence (PS). Three character dimensions are also included: self-directedness (SD), cooperativeness (CO), and self-transcendence (ST).

Methods

We compared personality scores between diagnostic groups and assessed heritability in a sample of 101 families collected for genetic studies of BD. A genome-wide SNP linkage analysis was then performed in the subset of 51 families for which genetic data was available.

Results

Significant group differences were observed between BD subjects, their first-degree relatives, and independent controls for all but RD and PS, and all but HA and RD were found to be significantly heritable in this sample. Linkage analysis of the heritable dimensions produced several suggestive linkage peaks for NS (chromosomes 7q21 and 10p15), PS (chromosomes 6q16, 12p13, and 19p13), and SD (chromosomes 4q35, 8q24, and 18q12).

Limitations

The relatively small size of our linkage sample likely limited our ability to reach genome-wide significance in this study.

Conclusions

While not genome-wide significant, these results suggest that aspects of personality may prove useful in the identification of genes underlying BD susceptibility.     

Ethnic differences in seasonal affective disorder and associated factors among five immigrant groups in Norway

Background

Research studies on seasonal affective disorder (SAD) among immigrant populations are scarce. The objective of this article was to explore the associated risk and protective factors on prevalence of winter SAD (W-SAD), sub syndromal SAD (S-SAD) and Summer-SAD among five immigrant groups living in Oslo, Norway.

Methods

The Oslo Immigrants Health study (innvandrer HUBRO, 2002), is a large cross sectional epidemiological survey conducted among five of the largest immigrant groups living in Oslo. 1047 subjects were included in the analysis out of 3019 who participated in the survey. Mailed questionnaire which included selected items of the seasonal pattern assessment questionnaire (SPAQ), Hopkins symptom check list (HSCL) and other variables were used in the analysis.

Results

The lowest levels of W-SAD were found among Sri Lankan men and women and the highest among Iranians. W-SAD was significantly associated with country of birth, younger age, smoking, presence of mental distress, frequent visits to general practitioner or psychiatrist, self reported poor health and presence of chronic disorders. S-SAD was significantly associated with country of birth, smoking and higher levels of alcohol consumption.

Limitations

SPAQ was not culturally validated. Poor response rate (39.7%) can also be considered as a limitation.

Conclusions

Ethnic differences in W-SAD and S-SAD were observed. Sri Lankans had the lowest levels of W-SAD. However, there is a need for culturally validated instruments and further research must focus on exploring protective factors for SAD.     

The reliability and validity of the Seasonal Pattern Assessment Questionnaire: a comparison between patient groups

Background: The Seasonal Pattern Assessment Questionnaire (SPAQ) is a frequently used screening instrument in the research on Seasonal Affective Disorder (SAD). Nevertheless, studies on its reliability and validity are relatively scarce. In the present study the reliability and the contrast validity of the SPAQ are investigated. Methods: SAD patients, selected by means of a clinical interview, non-seasonal depressed out-patients, non-depressed out-patients, and a control group, are contrasted to estimate the discriminating power of the SPAQ. Also, the reliability and factor structure of the seasonality and the climate subscales are investigated. To study food intake the Seasonal Food Preference Questionnaire (SFPQ) was developed. Results: The SAD criterion of the SPAQ shows good specificity (94%), but a low sensitivity (44%). Discriminant analysis shows sufficient ability to classify subjects (81% correctly classified). The Global Seasonality Scale has a good internal consistency. It consists of two factors, a psychological factor and a food factor. The SFPQ is sensitive for carbohydrate intake by SAD patients. Limitations: Most SAD patients had received treatment and completed the SPAQ while they were not depressed, which may have influenced the sensitivity. Conclusions: The SPAQ is not sensitive enough to be considered a diagnostic instrument for SAD. Nevertheless, it is accurate enough to be used as a screenings instrument. The only false positives were found in the depressive group. The accuracy of prevalence Figs. can be improved by completion of the SPAQ in the summer months, combined with the completion of a depression scale.     

The stability of the Seasonal Pattern Assessment Questionnaire score index over time and the validity compared to classification according to DSM-III-R

BACKGROUND: In 1984, Rosenthal et al. described a group of patients characterised by repeated winter depression with atypical symptoms eventually followed by summer mania or hypomania (seasonal affective disorder, SAD). The relationship between SAD and the classical manic-depressive disorder is uncertain. The aim of this study was to validate the Seasonal Pattern Assessment Questionnaire (SPAQ) classification in relation to the DSM-III-R criteria of seasonal patterns in a group of patients with bipolar affective disorder and to evaluate the stability of the SPAQ score index over time. METHODS: A group of bipolar patients were followed for 3 years with examinations every third month and at hospitalisation. At inclusion and at each following examination the patients were rated with the Hamilton Depression Rating Scale, the Newcastle Depression Rating Scale, and the Bech-Rafaelsen Mania Rating Scale. At inclusion and once a year the patients completed the SPAQ. RESULTS: Fifty-six patients agreed to participate and 46 patients completed 1 year or more. Eight patients, all women, had at least one SPAQ score index (SSI) of 11 or more. Women scored significantly higher than men on SPAQ. The test/re-test reliability of SSI between two consecutive years was good, but decreased as the time difference between tests increased. Moreover, we found no relation between seasonal variations of affective episodes according to SSI and DSM-III-R. LIMITATIONS: The group of patients with seasonality according to DSM-III-R or SSI was small. CONCLUSION: The validity of SSI between two consecutive years is good, but decreases as the time difference between tests increases. There is no relationship between seasonality defined by DSM-III-R and SSI. Female bipolar patients show, as the general population, seasonal variations in mood, energy, sociality, appetite, and sleep independently of their affective episodes. SSI cannot be used for the prediction of seasonal variation in a group of bipolar patients.     

Delayed sleep phase syndrome is related to seasonal affective disorder

Background

Both delayed sleep phase syndrome (DSPS) and seasonal affective disorder (SAD) may manifest similar delayed circadian phase problems. However, the relationships and co-morbidity between the two conditions have not been fully studied. The authors examined the comorbidity between DSPS and SAD.

Methods

We recruited a case series of 327 DSPS and 331 controls with normal sleep, roughly matched for age, gender, and ancestry. Both DSPS and controls completed extensive questionnaires about sleep, the morningness-eveningness trait, depression, mania, seasonality of symptoms, etc.

Results

The prevalences of SAD and subsyndromal SAD (S-SAD) were higher in DSPS compared to controls (χ² = 12.65, p = 0.002). DSPS were 3.3 times more likely to report SAD (odds ratio, 3.34; 95% CI, 1.41-7.93) compared to controls as defined by the Seasonal Pattern Assessment Questionnaire (SPAQ). Correspondingly, DSPS showed significantly higher seasonality scores compared to controls in mood, appetite, and energy level subscores and the global seasonality score (t = 3.12, t = 0.002; t = 2.04, p = 0.041; t = 2.64, p = 0.008; and t = 2.15, p = 0.032, respectively). Weight fluctuation during seasons and winter-summer sleep length differences were also significantly higher in DSPS than controls (t = 5.16, p < 0.001 and t = 2.64, p = 0.009, respectively). SAD and S-SAD reported significantly higher eveningness, higher depression self-ratings, and more previous mania symptoms compared to non-seasonal subjects regardless of whether they were DSPS or controls.

Conclusions

These cases suggested that DSPS is partially comorbid with SAD. These data support the hypothesis that DSPS and SAD may share a pathophysiological mechanism causing delayed circadian phase.