The impact of latitude on the prevalence of seasonal depression

The Prevalence and Clinical Phenotypes of Cluster Headache in Relation with Latitude

PURPOSE OF REVIEW

Previous studies have indicated a possible link between the prevalence of cluster headache (CH) and sunlight exposure. However, this theory has yet to be tested systemically. In this article, we aim to examine how latitude affects the prevalence and phenotypes of CH.

RECENT FINDINGS

To our knowledge, there is by far no article describing the effect of latitude on disease phenotype; thus, we performed a literature review. We noted positive effects of latitude on 1-year prevalence, the proportion of chronic CH, and the proportion of miosis and/or ptosis. Latitude may affect the phenotypic presentations of cluster headache, probably partially mediated via temperature and sunlight variations. Still, other factors, such as environmental exposure to smoking and the genetic difference between the Eastern and Western populations, may participate in the pathogenesis and clinical manifestations of CH.

Utilizing Big Data From Google Trends to Map Population Depression in the United States: Exploratory Infodemiology Study

BACKGROUND

The epidemiology of mental health disorders has important theoretical and practical implications for health care service and planning. The recent increase in big data storage and subsequent development of analytical tools suggest that mining search databases may yield important trends on mental health, which can be used to support existing population health studies.

OBJECTIVE

This study aimed to map depression search intent in the United States based on internet-based mental health queries.

METHODS

Weekly data on mental health searches were extracted from Google Trends for an 11-year period (2010-2021) and separated by US state for the following terms: "feeling sad," "depressed," "depression," "empty," "insomnia," "fatigue," "guilty," "feeling guilty," and "suicide." Multivariable regression models were created based on geographic and environmental factors and normalized to the following control terms: "sports," "news," "google," "youtube," "facebook," and "netflix." Heat maps of population depression were generated based on search intent.

RESULTS

Depression search intent grew 67% from January 2010 to March 2021. Depression search intent showed significant seasonal patterns with peak intensity during winter (adjusted P<.001) and early spring months (adjusted P<.001), relative to summer months. Geographic location correlated with depression search intent with states in the Northeast (adjusted P=.01) having higher search intent than states in the South.

CONCLUSIONS

The trends extrapolated from Google Trends successfully correlate with known risk factors for depression, such as seasonality and increasing latitude. These findings suggest that Google Trends may be a valid novel epidemiological tool to map depression prevalence in the United States.

Second-generation antidepressants for treatment of seasonal affective disorder

BACKGROUND

Seasonal affective disorder (SAD) is a seasonal pattern of recurrent depressive episodes that is often treated with second-generation antidepressants (SGAs), light therapy, or psychotherapy.

OBJECTIVES

To assess the efficacy and safety of second-generation antidepressants (SGAs) for the treatment of seasonal affective disorder (SAD) in adults in comparison with placebo, light therapy, other SGAs, or psychotherapy.

SEARCH METHODS

This is an update of an earlier review first published in 2011. We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2020, Issue 1) in the Cochrane Library (all years), Ovid MEDLINE, Embase, and PsycINFO (2011 to January 2020), together with the Cochrane Common Mental Disorders Controlled Trials Register (CCMDCTR) (all available years), for reports of randomised controlled trials (RCTs). We hand searched the reference lists of all included studies and other systematic reviews. We searched ClinicalTrials.gov for unpublished/ongoing trials. We ran a separate update search for reports of adverse events in the Ovid databases.  SELECTION CRITERIA: For efficacy we included RCTs of SGAs compared with other SGAs, placebo, light therapy, or psychotherapy in adult participants with SAD. For adverse events we also included non-randomised studies.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened abstracts and full-text publications against the inclusion criteria. Data extraction and 'Risk of bias' assessment were conducted individually. We pooled data for meta-analysis where the participant groups were similar, and the studies assessed the same treatments with the same comparator and had similar definitions of outcome measures over a similar duration of treatment.

MAIN RESULTS

In this update we identified no new RCT on the effectiveness of SGAs in SAD patients. We included 2 additional single-arm observational studies that reported on adverse events of SGAs.  For efficacy we included three RCTs of between five and eight weeks' duration with a total of 204 participants. For adverse events we included two RCTs and five observational (non-randomised) studies of five to eight weeks' duration with a total of 249 participants. All participants met the DSM (Diagnostic and Statistical Manual of Mental Disorders) criteria for SAD. The average age ranged from 34 to 42 years, and the majority of participants were female (66% to 100%). Results from one trial with 68 participants showed that fluoxetine (20/36) was numerically superior to placebo (11/32) in achieving clinical response; however, the confidence interval (CI) included both a potential benefit as well as no benefit of fluoxetine (risk ratio (RR) 1.62, 95% CI 0.92 to 2.83, very low-certainty evidence). The number of adverse events was similar in both groups (very low-certainty evidence). Two trials involving a total of 136 participants compared fluoxetine versus light therapy. Meta-analysis showed fluoxetine and light therapy to be approximately equal in treating seasonal depression: RR of response 0.98 (95% CI 0.77 to 1.24, low-certainty evidence), RR of remission 0.81 (95% CI 0.39 to 1.71, very low-certainty evidence). The number of adverse events was similar in both groups (low-certainty evidence). We did not identify any eligible study comparing SGA with another SGA or with psychotherapy. Two RCTs and five non-randomised studies reported adverse event data on a total of 249 participants who received bupropion, fluoxetine, escitalopram, duloxetine, nefazodone, reboxetine, light therapy, or placebo. We were only able to obtain crude rates of adverse events, therefore caution is advised regarding interpretation of this information. Between 0% and 100% of participants who received an SGA suffered an adverse event, and between 0% and 25% of participants withdrew from the study due to adverse events.

AUTHORS' CONCLUSIONS

Evidence for the effectiveness of SGAs is limited to one small trial of fluoxetine compared with placebo showing a non-significant effect in favour of fluoxetine, and two small trials comparing fluoxetine against light therapy suggesting equivalence between the two interventions. The lack of available evidence precluded us from drawing any overall conclusions on the use of SGAs for SAD. Further, larger RCTs are required to expand and strengthen the evidence base on this topic, and should also include comparisons with psychotherapy and other SGAs. Data on adverse events were sparse, and a comparative analysis was not possible. The data we obtained on adverse events is therefore not robust, and our confidence in the data is limited. Overall, up to 25% of participants treated with SGAs for SAD withdrew from the study early due to adverse events.

Seasonal variation in symptoms of depression: A Canadian population based study

BACKGROUND

There is no consensus as to whether depressive symptoms vary by season. Using data from the Canadian Community Health Survey (CCHS), the purpose of this study was to evaluate seasonal variation in depressive symptoms in the Canadian household population.

METHODS

A cross-sectional analysis of data from the CCHS in 2015 and 2016 was used. Mean Patient Health Questionnaire-9 (PHQ-9) scores, and categories defined by 5+ or 10+ cut-points were used for analysis. Seasonal effects were assessed using quadratic terms in regression models, generalized linear models were used for this purpose. Models were stratified by youth ages 12-24 (rounded n ≈ 8000) and adults ages 25+ (rounded n ≈ 45,000).

RESULTS

Significant seasonal variation was observed for youth (age 12-24) for mean PHQ-9 scores and proportion with scores of 5+. There was evidence of effect modification by age. The youth group had stronger seasonal effects compared to respondents age 25+. Seasonal effect was highly significant for mean PHQ-9 scores (p = 0.009) and 5+ (p = 0.001), but not for 10+ (p = 0.481).

LIMITATIONS

Use of cross-sectional data limits the capacity to generalize results to the classic definition of Seasonal Affective Disorder. Data surrounding respondent's anti-depressant use was unavailable.

CONCLUSIONS

Seasonal variation in depressive symptoms is evident in the Canadian population. Higher levels of symptoms were reported in winter months compared to summer months. The seasonal trend is most pronounced in youth specifically those who reported at least mild depressive symptoms, but not in respondents reporting moderate to severe symptoms.

Seasonality of antidepressant prescriptions and sick leaves

The aim of the present study was to estimate the number of patients with a seasonal prescription pattern of antidepressants, which might be taken as a surrogate marker for medicated patients with seasonal affective disorder (SAD). Furthermore, we examined the time course of sick leaves for patients with seasonal and non-seasonal prescriptions of antidepressants. A retrospective analysis of prescription data of all patients insured by the Sickness Fund Burgenland (BGKK) between 2005 and 2016 was performed. Patients with treatment initiation of an antidepressant in the last and first quarter of the year for at least two consecutive years were selected (SAD-med). Patients with continuation treatment in the third quarter and patients with initiation of antidepressant medication in the second and third quarter of the year were excluded. The mean yearly prescription rate for antidepressants was 9.6% in the insured population. 3.0% of patients treated with antidepressants and 0.9% of insured cases satisfied the definition of SAD-med. The mean number of yearly sick leave days was similar for SAD-med patients and those with non-seasonal prescriptions. Time series analysis showed that sick leaves in SAD-med were influenced by seasonal fluctuations for several years after the first antidepressant prescription. Our study sheds light on antidepressant prescription and sick leave patterns in the general population. Compared to the prevalence of SAD, the estimated rate of SAD-med is substantial. Sick leaves appear to be closely linked to antidepressant prescriptions, and show a characteristic time course before and after the initial prescription.

Major Depression Prevalence Increases with Latitude in Canada

OBJECTIVE

To determine whether there is an association between latitude and annual major depressive episode (MDE) prevalence in Canada.

METHODS

Data from 2 national survey programs (the National Population Health Survey and the Canadian Community Health Survey) were used, providing 10 data sets collected between 1996 and 2013, together including 922,260 respondents, of whom 495,739 were assessed for MDE using 1 of 2 versions of the Composite International Diagnostic Interview, a short-form version (8 studies), and a Canadian adaptation of the World Mental Health version (2 studies). Approximate latitude was determined by linkage to postal code data. Data were analyzed using logistic regression and pooled across surveys using individual-level meta-analytic methods.

RESULTS

In models including latitude as a continuous variable, a statistically significant association was observed, with prevalence increasing with increasing latitude. This association persisted after adjustment for a set of known risk factors. The latitude gradient was modest in magnitude, a 1% to 2% increase in the prevalence odds of MDE per degree of latitude was observed. Due to sparse data, this gradient cannot be confidently generalized beyond major population centres, which tend to occur at less than 55° latitude in Canada.

CONCLUSION

A latitude gradient has not previously been reported. If replicated, the gradient may have implications for the planning of services and generation of aetiological hypotheses. However, this cross-sectional analysis cannot confirm aetiology and could not evaluate the potential contributions of variables such as light exposure, weather patterns, or social determinants.

Pupillary response abnormalities in depressive disorders

Depressive disorders lack objective physiological measurements to characterize the affected population and facilitate study of relevant mechanisms. The melanopsin-mediated light signaling pathway may contribute to seasonal variation and can be measured non-invasively by pupillometry. We prospectively studied changes in melanopsin-mediated pupillary constriction in 19 participants with major depressive disorder (MDD) and 10 control across the summer and winter solstices. The melanopsin-mediated response, as measured by the pupil's sustained constriction six s after a high intensity blue light stimulus, was marginally attenuated in those with MDD relative to controls (p=0.071). The participants with MDD unexpectedly showed a significantly reduced transient pupillary response to low intensity red (p=0.011) and blue light (p=0.013), but not high intensity red and blue light. Sustained pupillary constriction in response to high intensity blue light was more pronounced with increasing daylight hours (p=0.037) and was more strongly related to objectively measured versus estimated light exposure. Melanopsin-mediated impairments in pupil response may serve as a biological marker for vulnerability to depression in low light conditions. Assessment of these and other responses to light stimuli, such as response to low intensity light, may be useful for the study of the neurobiology of MDD and related mood disorders.

Are short (blue) wavelengths necessary for light treatment of seasonal affective disorder?

Despite widely published speculation regarding a potential potency advantage of short-wavelength (blue-appearing) light for Seasonal Affective Disorder (SAD) treatment, there have been few systematic studies. Those comparing short-wavelength to broad-wavelength (white) light under actual clinical conditions suggest equivalent effectiveness. This multicenter, parallel-group design trial was undertaken to compare the effects of light therapy on SAD using blue (~465 nm) versus blue-free (595-612 nm) LED lights. Fifty-six medication-free subjects aged 21-64 years who met DSM-IV-TR criteria for recurrent major depression with winter-type seasonal pattern were enrolled in this blinded study at five participating centers between January and March 2012. Thirty-five subjects met the criteria for randomization to 30 min of either blue (~465 nm) or blue-free (595-612 nm) daily morning light therapy. Twenty-nine subjects completed the study; three subjects withdrew due to treatment-related adverse events, including migraines, and three withdrew for non-study-related reasons. The primary effectiveness variable was depression score (SIGH-ADS) after six weeks of daily light treatment. Secondary effectiveness variables included quality-of-life (QoL) and suicidality ratings. Using an intent-to-treat analysis, mean depression scores were different at baseline for the blue group (29 ± 5 versus 26 ± 5, p = 0.05 blue versus blue-free, respectively), and the initial score was used as a covariate. Baseline scores were not significantly different between treatment groups among those who completed the study, and no significant differences in depression scores were observed after 6 weeks (mean ± SD scores at 6 weeks: 5.6 ± 6.1 versus 4.5 ± 5.3, p = 0.74, blue versus blue-free, respectively). In addition, the proportion of subjects who met remission criteria, defined as a depression score ≤8, was not significantly different between the two groups (p = 0.41); among the 29 subjects who completed the study, 76% of subjects experienced remission by the end of the trial, which coincided with the beginning of spring. The QoL and suicidality ratings were also significantly improved from pre- to post-treatment, with no significant difference between treatments. No subject experienced worsening or non-improved symptoms over the 6-week trial. The main finding of this study is that subjects treated with blue light did not improve more than subjects treated with blue-free light; both showed substantial improvement on multiple measures. Failure to find differences may have resulted from methodological constraints, including a small sample size. Recruitment began mid-winter during an unusually mild season, and the trial was terminated earlier than planned by the study sponsor due to a failure to detect a difference. However, if confirmed in a larger randomized sample, these results suggest that blue wavelengths are not necessary for successful SAD treatment.

Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders

OBJECTIVES

To provide guidance for the management of mood disorders, based on scientific evidence supplemented by expert clinical consensus and formulate recommendations to maximise clinical salience and utility.

METHODS

Articles and information sourced from search engines including PubMed and EMBASE, MEDLINE, PsycINFO and Google Scholar were supplemented by literature known to the mood disorders committee (MDC) (e.g., books, book chapters and government reports) and from published depression and bipolar disorder guidelines. Information was reviewed and discussed by members of the MDC and findings were then formulated into consensus-based recommendations and clinical guidance. The guidelines were subjected to rigorous successive consultation and external review involving: expert and clinical advisors, the public, key stakeholders, professional bodies and specialist groups with interest in mood disorders.

RESULTS

The Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for mood disorders (Mood Disorders CPG) provide up-to-date guidance and advice regarding the management of mood disorders that is informed by evidence and clinical experience. The Mood Disorders CPG is intended for clinical use by psychiatrists, psychologists, physicians and others with an interest in mental health care.

CONCLUSIONS

The Mood Disorder CPG is the first Clinical Practice Guideline to address both depressive and bipolar disorders. It provides up-to-date recommendations and guidance within an evidence-based framework, supplemented by expert clinical consensus.

MOOD DISORDERS COMMITTEE

Professor Gin Malhi (Chair), Professor Darryl Bassett, Professor Philip Boyce, Professor Richard Bryant, Professor Paul Fitzgerald, Dr Kristina Fritz, Professor Malcolm Hopwood, Dr Bill Lyndon, Professor Roger Mulder, Professor Greg Murray, Professor Richard Porter and Associate Professor Ajeet Singh.

INTERNATIONAL EXPERT ADVISORS

Professor Carlo Altamura, Dr Francesco Colom, Professor Mark George, Professor Guy Goodwin, Professor Roger McIntyre, Dr Roger Ng, Professor John O'Brien, Professor Harold Sackeim, Professor Jan Scott, Dr Nobuhiro Sugiyama, Professor Eduard Vieta, Professor Lakshmi Yatham.

AUSTRALIAN AND NEW ZEALAND EXPERT ADVISORS

Professor Marie-Paule Austin, Professor Michael Berk, Dr Yulisha Byrow, Professor Helen Christensen, Dr Nick De Felice, A/Professor Seetal Dodd, A/Professor Megan Galbally, Dr Josh Geffen, Professor Philip Hazell, A/Professor David Horgan, A/Professor Felice Jacka, Professor Gordon Johnson, Professor Anthony Jorm, Dr Jon-Paul Khoo, Professor Jayashri Kulkarni, Dr Cameron Lacey, Dr Noeline Latt, Professor Florence Levy, A/Professor Andrew Lewis, Professor Colleen Loo, Dr Thomas Mayze, Dr Linton Meagher, Professor Philip Mitchell, Professor Daniel O'Connor, Dr Nick O'Connor, Dr Tim Outhred, Dr Mark Rowe, Dr Narelle Shadbolt, Dr Martien Snellen, Professor John Tiller, Dr Bill Watkins, Dr Raymond Wu.

Natural light exposure, sleep and depression among day workers and shiftworkers at arctic and equatorial latitudes

OBJECTIVES

This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year.

METHODS

This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273).

RESULTS

The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep.

CONCLUSION

Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.

Graph theory reveals hyper-functionality in visual cortices of Seasonal Affective Disorder patients

OBJECTIVES

Seasonal affective disorder (SAD) is a subtype of recurrent unipolar or bipolar depressive disorder with a higher prevalence in winter than in summer. The biological underpinnings of SAD are so far poorly understood. Studies examining SAD have found disturbances between the molecular and connectivity scales. The aim of the study was to explore changes in functional connectivity typical for SAD.

METHODS

We investigated unmedicated, untreated SAD patients and healthy controls using resting-state functional magnetic resonance imaging (rs-fMRI) utilizing graph theory, a data driven and hypothesis free approach, to model functional networks of the brain.

RESULTS

Comparing whole brain network properties using graph theory we observed globally affected network topologies with increasing pathlength in SAD. Nodal changes, however, were highly restricted to bilateral inferior occipital cortex. Interestingly, we found a lateralization where hyper-connectedness was restricted to right inferior occipital cortex and hyper-efficiency was found in the left inferior occipital cortex. Furthermore, we found these nodes became more "hub like" in patients, suggesting a greater functional role.

CONCLUSIONS

Our work stresses the importance of abnormal intrinsic processing during rest, primarily affecting visual areas and subsequently changing whole brain networks, and thus providing an important hint towards potential future therapeutic approaches.

The influence of light administration on interpersonal behavior and affect in people with mild to moderate seasonality

Bright light is used to treat winter depression and may also have positive effects on mood in some healthy individuals. However, there is little information on how bright light treatment influences social behavior. We performed a cross-over study in winter comparing the effects of morning bright light administration with placebo (exposure to negative ions) on mood and social behavior in 38 healthy people with mild to moderate seasonality. Each treatment was given for 21days with a washout period of 14days between treatments. An event-contingent recording assessment was used to measure mood, and social behavior along two axes, agreeable-quarrelsome and dominant-submissive, during each 21-day treatment period. During treatments, participants wore a combined light-sensor and accelerometer to test this method for adherence to light treatment self-administered at home. Data were analyzed using multilevel modeling. Bright light improved mood but increased quarrelsome behavior and decreased submissiveness. Data from the light monitor and accelerometer suggested that 21% of the participants did not adhere to bright light treatment; when this group was analyzed separately, there was no change in quarrelsomeness or mood. However, results for individuals who followed the procedure were similar to those reported for the whole sample.

Common sense: folk wisdom that ethnobiological and ethnomedical research cannot afford to ignore

Common sense [CS], especially that of the non-scientist, can have predictive power to identify promising research avenues, as humans anywhere on Earth have always looked for causal links to understand, shape and control the world around them. CS is based on the experience of many individuals and is thus believed to hold some truths. Outcomes predicted by CS are compatible with observations made by whole populations and have survived tests conducted by a plethora of non-scientists. To explore our claim, we provide 4 examples of empirical insights (relevant to probably all ethnic groups on Earth) into causal phenomena predicted by CS: (i) "humans must have a sense of time", (ii) "at extreme latitudes, more people have the winter blues", (iii) "sleep is a cure for many ills" and (iv) "social networks affect health and disease". While CS is fallible, it should not be ignored by science - however improbable or self-evident the causal relationships predicted by CS may appear to be.

Seasonality of mood and behavior in the Old Order Amish

BACKGROUND/OBJECTIVE

We examined seasonality and winter seasonal affective disorder (SAD) in the Old Order Amish of Lancaster County, Pennsylvania, a unique population that prohibits use of network electric light in their homes.

METHODS

We estimated SAD using the seasonal pattern assessment questionnaire (SPAQ) in 1306 Amish adults and compared the frequencies of SAD and total SAD (i.e., presence of either SAD or subsyndromal-SAD) between men and women, young and old, and awareness of (ever vs. never heard about) SAD. Heritability of global seasonality score (GSS) was estimated using the maximum likelihood method, including a household effect to capture shared environmental effects.

RESULTS

The mean (±SD) GSS was 4.36 (±3.38). Prevalence was 0.84% (95% CI: 0.36-1.58) for SAD and 2.59% (95% CI: 1.69-3.73) for total SAD. Heritability of GSS was 0.14±0.06 (SE) (p=0.002) after adjusting for age, gender, and household effects.

LIMITATIONS

Limitations include likely overestimation of the rates of SAD by SPAQ, possible selection bias and recall bias, and limited generalizability of the study.

CONCLUSIONS

In the Amish, GSS and SAD prevalence were lower than observed in earlier SPAQ-based studies in other predominantly Caucasian populations. Low heritability of SAD suggests dominant environmental effects. The effects of awareness, age and gender on SAD risk were similar as in previous studies. Identifying factors of resilience to SAD in the face of seasonal changes in the Amish could suggest novel preventative and therapeutic approaches to reduce the impact of SAD in the general population.

Bright-light therapy in the treatment of mood disorders

Bright-light therapy (BLT) is established as the treatment of choice for seasonal affective disorder/winter type (SAD). In the last two decades, the use of BLT has expanded beyond SAD: there is evidence for efficacy in chronic depression, antepartum depression, premenstrual depression, bipolar depression and disturbances of the sleep-wake cycle. Data on the usefulness of BLT in non-seasonal depression are promising; however, further systematic studies are still warranted. In this review, the authors present a comprehensive overview of the literature on BLT in mood disorders. The first part elucidates the neurobiology of circadian and seasonal adaptive mechanisms focusing on the suprachiasmatic nucleus (SCN), the indolamines melatonin and serotonin, and the chronobiology of mood disorders. The SCN is the primary oscillator in humans. Indolamines are known to transduce light signals into cells and organisms since early in evolution, and their role in signalling change of season is still preserved in humans: melatonin is synthesized primarily in the pineal gland and is the central hormone for internal clock circuitries. The melatonin precursor serotonin is known to modulate many behaviours that vary with season. The second part discusses the pathophysiology and clinical specifiers of SAD, which can be seen as a model disorder for chronobiological disturbances and the mechanism of action of BLT. In the third part, the mode of action, application, efficacy, tolerability and safety of BLT in SAD and other mood disorders are explored.

Second-generation antidepressants for seasonal affective disorder

BACKGROUND

Seasonal affective disorder (SAD) is a seasonal pattern of recurrent depressive episodes that is often treated with second-generation antidepressants (SGAs), light therapy or psychotherapy.

OBJECTIVES

To assess the efficacy and safety of SGAs for the treatment of SAD in adults in comparison with placebo, light therapy, other SGAs or psychotherapy.

SEARCH METHODS

We searched the Cochrane Depression, Anxiety and Neuorosis Review Group's specialised register (CCDANCTR) on the 26 August 2011. The CCDANCTR contains reports of relevant randomised controlled trials from The Cochrane Library (all years), EMBASE (1974 to date), MEDLINE (1950 to date) and PsycINFO (1967 to date). In addition, we searched pharmaceutical industry trials registers via the Internet to identify unpublished trial data. Furthermore, we searched OVID MEDLINE, MEDLINE In-process, EMBASE and PsycINFO to 27July 2011 for publications on adverse effects (including non-randomised studies).

SELECTION CRITERIA

For efficacy we included randomised trials of SGAs compared with other SGAs, placebo, light therapy or psychotherapy in adult participants with SAD. For adverse effects we also included non-randomised studies.

DATA COLLECTION AND ANALYSIS

Two review authors screened abstracts and full-text publications against the inclusion criteria. Data abstraction and risk of bias assessment were conducted by one reviewer and checked for accuracy and completeness by a second. We pooled data for meta-analysis where the participant groups were similar and the studies assessed the same treatments with the same comparator and had similar definitions of outcome measures over a similar duration of treatment.

MAIN RESULTS

For efficacy we included three randomised trials of between five and eight weeks duration with a total of 204 participants. For adverse effects we included two randomised trials and three observational (non-randomised) studies of five to eight weeks duration with a total of 225 participants. Overall, the randomised trials had low-to-moderate risk of bias, and the observational studies had a high risk of bias (due to small size and high attrition). The participants in the studies all met DSM (Diagnostic and Statistics Manual of Mental Disorders) criteria for SAD. The average age was approximately 40 years and 70% of the participants were female.Results from one trial with 68 participants showed that fluoxetine was not significantly more effective than placebo in achieving clinical response (risk ratio (RR) 1.62, 95% confidence interval (CI) 0.92 to 2.83). The number of adverse effects were similar between the two groups.We located two trials that contained a total of 136 participants for the comparison fluoxetine versus light therapy. Our meta-analysis of the results of the two trials showed fluoxetine and light therapy to be approximately equal in treating seasonal depression: RR of response 0.98 (95% CI 0.77 to 1.24), RR of remission 0.81 (95% CI 0.39 to 1.71). The number of adverse effects was similar in both groups.Two of the three randomised trials and three non-randomised studies contained adverse effect data on 225 participants who received fluoxetine, escitalopram, duloxetine, reboxetine, light therapy or placebo. We were only able to obtain crude rates of adverse effects, so any interpretation of this needs to be undertaken with caution. Between 22% and 100% of participants who received a SGA suffered an adverse effect and between 15% and 27% of participants withdrew from the studies because of adverse effects.

AUTHORS' CONCLUSIONS

Evidence for the effectiveness of SGAs is limited to one small trial of fluoxetine compared with placebo, which shows a non-significant effect in favour of fluoxetine, and two small trials comparing fluoxetine against light therapy, which suggest equivalence between the two interventions. The lack of available evidence precludes the ability to draw any overall conclusions on the use of SGAs for SAD. Further larger RCTs are required to expand and strengthen the evidence base on this topic, and should also include comparisons with psychotherapy and other SGAs.Data on adverse events were sparse, and a comparative analysis was not possible. Therefore the data we obtained on adverse effects is not robust and our confidence in the data is limited. Overall, up to 27% of participants treated with SGAs for SAD withdrew from the studies early due to adverse effects. The overall quality of evidence in this review is very low.

What is this thing called “SAD”? A critique of the concept of seasonal affective disorder

Background– Seasonal Affective Disorder (SAD) is supposed to be caused by lack of daylight in winter. Yet the population of Northern Norway, living without sun for two winter months, does not spontaneously complain about depression during the dark period.Aims– To summarize research bearing upon the validity of the concept of SAD.Method– Review of relevant literature concerning the epidemiology of SAD and the questionnaire developed to measure it in general populations, the Seasonal Pattern Assessment Questionnaire (SPAQ).Results– Large population studies from northern Norway do not point to a higher prevalence of depression in winter than expected in any other general population. The psychometric properties of SPAQ are rather poor, and the diagnosis of SAD based on SPAQ bears little relationship to a meaningful concept of depression.Conclusions– Seasonal Affective Disorder is not a valid medical construct. Instead, “Recurrent depression with seasonal pattern” as defined in the DSM-IV and the ICD-10 should be used as terms. However, more research is needed to establish whether it is at all fruitful to single out such a subtype of recurrent depression.

Declaration of Interest: None.

Seasonal severity of depressive symptoms as a predictor of health service use in a community-based sample

OBJECTIVE

To determine whether severity of seasonal depressive symptoms is an independent predictor of depression-specific health service use.

METHODS

Cross-sectional telephone survey evaluating mood-related symptom changes across seasons using a structured interview based on the World Mental Health Composite International Diagnostic Interview, in a community sample representative of the province of Ontario, Canada (N = 1605). This study focuses on the 625 individuals (out of a total of 1605 interviewed) who screened positive for lifetime depressive symptoms. Severity of seasonal symptoms of depression (or "seasonality") was measured using the Seasonal Depression Severity (SDS) score (range 0-36). The primary outcome was lifetime depression-specific use of health services from a physician (family physician or psychiatrist). Lifetime psychotropic medication use, use of health services from a non-physician therapist, and psychiatric hospitalization were secondary outcomes. Other important variables that are known to predict depression-specific health service use were considered in multivariable analysis.

RESULTS

In our sample of individuals with depressive symptoms, those who had used physician health services had higher SDS scores than non-users (11.5 (SD 7.2) vs. 9.7 (SD 6.4), t(616) = 3.182, P = 0.001). In multivariable analysis, SDS score was independently associated with depression-specific health service use by a physician (OR = 1.04, 95% CI 1.01-1.07, p = 0.004). The relationship between seasonality and use of psychotropic medication use was similar (OR = 1.04, 95% CI 1.01-1.07, p = 0.007).

CONCLUSIONS

Seasonality was independently associated with depression-specific health service use for individuals with depressive symptoms. The results imply that greater seasonality may independently reflect increased severity and need for treatment of depression.

Do seasons have an influence on the incidence of depression? The use of an internet search engine query data as a proxy of human affect

BACKGROUND

Seasonal depression has generated considerable clinical interest in recent years. Despite a common belief that people in higher latitudes are more vulnerable to low mood during the winter, it has never been demonstrated that human's moods are subject to seasonal change on a global scale. The aim of this study was to investigate large-scale seasonal patterns of depression using Internet search query data as a signature and proxy of human affect.

METHODOLOGY/PRINCIPAL FINDINGS

Our study was based on a publicly available search engine database, Google Insights for Search, which provides time series data of weekly search trends from January 1, 2004 to June 30, 2009. We applied an empirical mode decomposition method to isolate seasonal components of health-related search trends of depression in 54 geographic areas worldwide. We identified a seasonal trend of depression that was opposite between the northern and southern hemispheres; this trend was significantly correlated with seasonal oscillations of temperature (USA: r = -0.872, p<0.001; Australia: r = -0.656, p<0.001). Based on analyses of search trends over 54 geological locations worldwide, we found that the degree of correlation between searching for depression and temperature was latitude-dependent (northern hemisphere: r = -0.686; p<0.001; southern hemisphere: r = 0.871; p<0.0001).

CONCLUSIONS/SIGNIFICANCE

Our findings indicate that Internet searches for depression from people in higher latitudes are more vulnerable to seasonal change, whereas this phenomenon is obscured in tropical areas. This phenomenon exists universally across countries, regardless of language. This study provides novel, Internet-based evidence for the epidemiology of seasonal depression.

Seasonal trends in depressive problems among United States children and adolescents: a representative population survey

This study examined season-of-assessment differences in parent and child reports of depressive problems on well-validated instruments in 2009 U.S. children and adolescents, aged 6 to 18 years, from a nationally representative population survey. A parent completed the Child Behavior Checklist (CBCL) for each participant and 1226 of the 11-18-year-olds completed the Youth Self-Report (YSR). Outcome measures were CBCL and YSR withdrawn/depressed syndrome scale scores and rates of clinically elevated scores. Overall fall/winter versus spring/summer differences were not found on the CBCL or YSR for depressive problem severity or rates of depressive problems. Age, sex, and latitude were examined as potential moderators of the association between season-of-assessment and the outcomes. Of these, the effect of season-of-assessment on CBCL depressive problem severity depended upon age. Parents of 16-18-year-old adolescents rated depressive problems as significantly more severe in fall and winter than in spring and summer. Parents also rated depressive problems as significantly more severe in 16-18-year-olds than in 6-15-year-olds, but only when assessed in the fall and winter. There were no season-of-assessment differences among 6-15-year-old children and adolescents. The overall lack of season-of-assessment differences and the finding of age as a moderator on only one of four outcomes suggest minimal seasonality effects.

Prevalence of self-reported seasonal affective disorders and the validity of the seasonal pattern assessment questionnaire in young adults Findings from a Swiss community study

BACKGROUND

The objective of this study was to expand the knowledge on the prevalence of self-reported Seasonal Affective Disorder (SAD) and to further study the validity of the Seasonal Pattern Assessment Questionnaire (SPAQ).

METHODS

A total of N=844 young adults were assessed in a Swiss community study by use of the SPAQ, a Seasonal Affective Disorders Questionnaire (SADQ), the Young Adult Self Report (YASR), the Centre for Epidemiologic Depression Scale (CES-D), and scales for measuring self-esteem, self-awareness and life events. At a second stage, a total of N=534 screen positives and controls were subjected to the Composite International Diagnostic Interview (M-CIDI) for the assessment of mental disorders. According to the SPAQ classification a group of SAD subjects and a group of subsyndromal SAD subjects (S-SAD) were defined. In addition, a third group of high-scoring depressives (HSD) subjects scoring above the 75th percentile of the CES-D was defined. Comparisons included these three groups and the rest of the sample serving as controls.

RESULTS

The weighted prevalence for SAD in this sample was 7.84% based on the SPAQ alone. With the addition of the SADQ, weighted prevalence rates dropped to 2.22%. Weighted subsyndromal SAD was 33.04%. Across the vast majority of scales, the SAD group was indistinguishable from the HSD group. These two groups scored highest, whereas the S-SAD group had an intermediate position and the controls had the lowest scores. SAD was best predicted by the CES-D total score.

CONCLUSIONS

The SPAQ as a single measure leads to an overestimation of SAD which, nevertheless, is a rather common phenomenon also in this central European population. The findings on the validity of the SPAQ are extended by showing that predominantly general aspects of depression are measured.

Epidemiologic heterogeneity of common mood and anxiety disorders over the lifecourse in the general population: a systematic review

BACKGROUND

Clinical evidence has long suggested there may be heterogeneity in the patterns and predictors of common mood and anxiety disorders; however, epidemiologic studies have generally treated these outcomes as homogenous entities. The objective of this study was to systematically review the epidemiologic evidence for potential patterns of heterogeneity of common mood and anxiety disorders over the lifecourse in the general population.

METHODS

We reviewed epidemiologic studies examining heterogeneity in either the nature of symptoms experienced ("symptom syndromes") or in patterns of symptoms over time ("symptom trajectories"). To be included, studies of syndromes were required to identify distinct symptom subtypes, and studies of trajectories were required to identify distinct longitudinal patterns of symptoms in at least three waves of follow-up. Studies based on clinical or patient populations were excluded.

RESULTS

While research in this field is in its infancy, we found growing evidence that, not only can mood and anxiety disorders be differentiated by symptom syndromes and trajectories, but that the factors associated with these disorders may vary between these subtypes. Whether this reflects a causal pathway, where genetic or environmental factors influence the nature of the symptom or trajectory subtype experienced by an individual, or whether individuals with different subtypes differed in their susceptibility to different environmental factors, could not be determined. Few studies addressed issues of comorbidity or transitions in symptoms between common disorders.

CONCLUSION

Understanding the diversity of these conditions may help us identify preventable factors that are only associated with some subtypes of these common disorders.

The prevalence of seasonal affective disorder (SAD) in Greenland is related to latitude

The aim of this study was to determine the prevalence of seasonal affective disorder (SAD) in Greenlanders and Danes living at four different latitudes in Greenland. A Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to 6021 men and women between the ages of 18 and 59 years living in four different municipalities in Greenland. The recipients were randomly selected from the National Population Register. Approximately 9% of the respondents met the criteria for SAD, and the incidence of SAD varied between a southern municipality and three northern municipalities. The prevalence of SAD was particularly high in northern municipalities. No significant difference was found in the prevalence of SAD between Greenlanders and Danes. The results are comparable with other population studies that have reported a high prevalence of SAD in arctic areas. The clinical implications of our findings and the possibilities for introducing light therapy should be assessed in future studies.

Seasonal vegetative and affective symptoms in the Finnish general population: testing the dual vulnerability and latitude effect hypotheses

BACKGROUND

Prior studies identified a seasonal pattern in symptoms of depression in clinical and population-based samples. The aims of our study were to estimate the prevalence rates of routine seasonal variations in mood and behavior and of current depressive symptoms in the Finnish general population over 30 years, and to find differences, if any, between the northern and southern regions of residence.

METHODS

5749 participants aged 30-97 (3156 women and 2593 men) were interviewed face to face and attended a health status examination. We included the modified Seasonal Pattern Assessment Questionnaire and the modified Beck Depression Inventory (BDI) for the analysis.

RESULTS

85% of the sample, representative of a general population, had seasonal variations in mood and behavior; 9% of the sample scored high on both scales, thus having the routine seasonal variations together with a current self-report of winter depression. Scoring high on the former scale yielded the odds ratio of 3.12 for scoring high on the BDI. Neither the global seasonality score nor the BDI sum score was associated with latitude. No significant differences in affective symptoms were found by the latitude. The seasonal variation in sleep duration (P<0.001) was more prevalent in the northern regions.

LIMITATIONS

The seasonal variations were assessed with a self-report only.

CONCLUSIONS

A seasonal pattern in mood and behaviors was detected in a general population. Implications of our findings include the assessment of the seasonal variations as a risk factor of depressive illness.

The chronobiology and neurobiology of winter seasonal affective disorder

This review summarizes research on the chronobiology and neurobiology of winter seasonal affective disorder (SAD), a recurrent subtype of depression characterized by a predictable onset in the fall/winter months and spontaneous remission in the spring/summer period. Chronobiological mechanisms related to circadian rhythms, melatonin, and photoperiodism play a significant role in many cases of SAD, and treatment of SAD can be optimized by considering individual differences in key chronobiological markers. Converging evidence also points to a role for the major monoamine neurotransmitters serotonin, norepinephrine, and dopamine in one or more aspects of SAD. Ultimately, as with other psychiatric illnesses, SAD is best considered as a complex disorder resulting from the interaction of several vulnerability factors acting at different levels, the various genetic mechanisms that underlie them, and the physical environment. Models of SAD that emphasize its potential role in human evolution will also be discussed.

Long-term and preventative treatment for seasonal affective disorder

Recurrent major depressive disorder with regular seasonal patterns, commonly known as seasonal affective disorder (SAD), has evoked substantial research in the last two decades. It is now recognised that SAD is a common condition with prevalence rates between 0.4% and 2.9% of the general population, and that patients with SAD experience significant morbidity and impairment in psychosocial function. There is good evidence that bright light therapy and antidepressant medications are effective for the short-term treatment of SAD; however, given that SAD is characterised by recurrent major depressive episodes, long-term and maintenance treatment must be considered. Unfortunately, there are few studies of longer term (>8 weeks) and maintenance (preventative) treatments for SAD. The weight of evidence suggests that light therapy usually needs to be continued daily throughout the winter season because of rapid relapse when light is stopped too early in the treatment period. However, some studies support the use of antidepressants to continue the response from a brief (1-2 weeks) course of light therapy early in the depressive episode, as soon as the first symptoms emerge in autumn. Only small studies have examined preventative treatment (before onset of symptoms) with light therapy, all of which have methodological limitations. The best evidence for preventative treatment in SAD comes from antidepressant studies. Three large, randomised, placebo-controlled studies have shown that preventative treatment with bupropion XL reduces the recurrence rate of depressive episodes in patients with SAD. Given the limitations in the evidence base and the inconsistent recurrence rate of winter depressive episodes, clinical recommendations for long-term and preventative treatment must individualise treatment choices and weigh potential benefits against possible adverse effects.

Is current alcohol consumption associated with increased lifetime prevalence of major depression and suicidality? Results from a pilot community survey

OBJECTIVE

Alcohol use disorders are associated with increased illness severity and suicidality in major depressive disorder (MDD). However, little is known about how alcohol use across the continuum relates to MDD.

METHOD

Subjects were 496 adults (201 men, 295 women) who completed a community-based telephone survey that incorporated a validated structured diagnostic interview for depression and a validated alcohol questionnaire. Subjects were divided into 3 alcohol consumption groups based on Canadian low-risk drinking guidelines: minimal (MIN), moderate (MOD), and heavy (HVY) alcohol consumption.

RESULTS

Among subjects with MDD, drinking group was not associated with measures of disability, health service use, or life satisfaction. Among all women, the prevalence of depression increased significantly across drinking groups (MIN, 24.6%; MOD, 30.3%; HVY, 44.0% [linear-by-linear association chi(2) = 4.1, df = 1, P < .05]), as did the prevalence of suicidality among women with MDD (MIN, 16.3%; MOD, 29.6%; HVY, 45.5% [chi(2) = 4.5, df = 1, P < .05]).

CONCLUSION

A range of alcohol consumption, not just heavy drinking, may be associated with major depression and suicidality.

High prevalence of self-reported depressive mood during the winter season among Swedish senior high school students

OBJECTIVE

There are few studies regarding the prevalence of seasonal variation in mood among children and adolescents. The main objective of this study was to estimate the prevalence of self-reported depressive mood during the winter season among Swedish adolescents and to investigate gender differences. Another aim was to analyze the factor structure and internal consistency of the Kiddie SPAQ (K-SPAQ), a pediatric version of the Seasonal Pattern Questionnaire (SPAQ).

METHOD

All students 17 to 18 years old, registered in the second year of senior high school in Falun, a district in central Sweden, were screened with the K-SPAQ in January 2003 (response rate 87.3%, n = 756).

RESULTS

The prevalence of self-reported depressive mood during the winter season was estimated at 20.1% (n = 151/751) and was higher among girls (25.5%) than boys (13.8%). Approximately 8% reported more severe depressive symptoms. Depressive mood during the summer was rare (0.1%, n = 1/751). Factor analysis of the General Seasonal Score items in the K-SPAQ revealed a two-factor structure. A Cronbach's alpha of 0.87 demonstrated a good internal consistency.

CONCLUSIONS

Depressive symptoms during autumn and winter were common among Swedish senior high school students, especially among girls. This is probably an underdiagnosed condition among adolescents that ought to receive more attention from the health and school authorities.

High prevalence of self-reported winter depression in a Swedish county

The prevalence of winter depression was unknown in Sweden, therefore prevalence figures of seasonal affective disorder (SAD) and subsyndromal SAD (S-SAD) were estimated. Age and gender differences, prevalence in the group of non-responders and some psychometric qualities of the Seasonal Pattern Assessment Questionnaire (SPAQ) were calculated. A modified version of the SPAQ was sent to a random sample of 2500 persons (response rate 66.3%, n=1657) between 18 and 64 years residing in Dalarna, a county in central Sweden. The sample was proportionally stratified according to age, gender and home municipality. The prevalence of winter SAD was estimated at 8% and S-SAD at 10.8%. It was approximately twice as common among women and younger persons. A total of 3.1% reported seasonal problems to be severe or disabling and 19.3% that everyday life was negatively affected. Experiencing seasonally changing depressive symptoms was common in the population. Factor analysis of the Global Seasonal Score resulted in one factor and the internal consistency was 0.88 (Cronbach's alpha). The results indicate that self-reported recurrent depression during winter is common in Sweden and should therefore receive more attention from health care authorities.

The diagnosis, symptomatology, and epidemiology of seasonal affective disorder

The operational criteria for seasonal affective disorder (SAD) have undergone several changes since first proposed in 1984. SAD is currently included as a specifier of either bipolar or recurrent major depressive disorder in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. The International Classification of Diseases, Tenth Edition has provisional diagnostic criteria for SAD. The most characteristic quality of SAD is that the symptoms usually present during winter and remit in the spring. Furthermore, the symptoms tend to remit when the patients are exposed to daylight or bright light therapy. The cognitive and emotional symptoms are as in other types of depression but the vegetative symptoms are the reverse of classic depressive vegetative symptoms, namely increased sleep and increased appetite. SAD is a common condition, but the exact prevalence rates vary between different studies and countries and is consistently found to be more common in women and in youth. SAD probably possibly occurs in children although not as commonly as in young adults. Some studies have found that certain ethnic groups who live at high northern latitudes may have adapted to the long arctic winter.

Update on the biology of seasonal affective disorder

The etiology and pathophysiology of seasonal affective disorder (SAD) has been linked to the seasons and to light since its first conceptualization. Aspects of SAD that make it particularly amenable to biological investigation include the predictable recurrent episodes, the rapid response to a nonpharmacologic treatment, the specific neurovegetative features, and the availability of rich animal models of seasonality. This paper reviews new findings for the major biological hypotheses for SAD, focusing on circadian rhythms, neurotransmitters, and molecular genetics. Integrative issues and future directions for the study of SAD, including the heuristic value of a dual-vulnerability hypothesis that conceptualizes seasonality as a dimensional construct and the importance of studying endophenotypes, will be discussed.

Seasonal affective disorder: a vestigial evolutionary advantage?

The typical symptoms of recurrent winter depression include lowered mood, lethargy, hypersomnia, social withdrawal, decreased libido, increased appetite and weight gain. Mild hypomania often occurs in spring and summer. It is argued that this pattern of attenuated hibernation constituted an adaptive evolutionary mechanism which enhanced the likelihood of reproductive success, most notably for females, among populations living at temperate latitudes. Women were more likely to become pregnant in the summer and thus to give birth at a time of year when their babies had a higher chance of survival. Winter depression symptoms also promoted healthier pregnancies and gave rise to enhanced female-male pair-bonding which improved the survival chances of both mothers and babies. Hypomania in spring and summer also served to increase the likelihood of procreation at the optimal time of year. In the modern era, it is probable that recurrent winter depression is becoming a reproductive disadvantage.

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.

Seasonal affective disorder: an overview

Seasonal Affective Disorder (SAD) is a condition of regularly occurring depressions in winter with a remission the following spring or summer. In addition to depressed mood, the patients tend to experience increased appetite and an increased duration of sleep during the winter. SAD is a relatively common condition, affecting 1-3% of adults in temperate climates, and it is more prevalent in women. The pathological mechanisms underlying SAD are incompletely understood. Certain neurotransmitters have been implicated; a dysfunction in the serotonin system in particular has been demonstrated by a variety of approaches. The role of circadian rhythms in SAD needs to be clarified. The phase-delay hypothesis holds that SAD patients' circadian rhythms are delayed relative to the sleep/wake or rest/activity cycle. This hypothesis predicts that the symptoms of SAD will improve if the circadian rhythms can be phase-advanced. There is some experimental support for this. SAD can be treated successfully with light therapy. In classical light therapy, the SAD sufferer sits in front of a light box, exposed to 2000-10,000 lux for 30-120 min daily during the winter. Other forms of light treatments, pharmacotherapy, and other therapies are currently being tested for SAD.