Is there a seasonal pattern of relapse in bipolar affective disorders? A dual northern and southern hemisphere cohort study

Clinical, sociodemographic and environmental predicting factors for relapse in bipolar disorder: A systematic review

INTRODUCTION

Bipolar disorder (BD) is a chronic and recurrent illness characterized by manic, mixed or depressive episodes, alternated with periods of euthymia. Several prognostic factors are associated with higher rates of relapse, which is crucial for the identification of high-risk individuals. This study aimed at systematically reviewing the existing literature regarding the impact of sociodemographic, clinical and environmental factors, in clinical relapses, recurrences and hospitalizations due to mood episodes in BD.

METHODS

A systematic search of electronic databases (PubMed, Cochrane library and Web of Science) was conducted to integrate current evidence about the impact of specific risk factors in these outcomes.

RESULTS

Fifty-eight articles met the inclusion criteria. Studies were grouped by the type of factors assessed. Family and personal psychiatric history, more severe previous episodes, earlier age of onset, and history of rapid cycling are associated with clinical relapses, along with lower global functioning and cognitive impairments. Unemployment, low educational status, poorer social adjustment and life events are also associated with higher frequency of episodes, and cannabis with a higher likelihood for rehospitalization.

LIMITATIONS

Small sample sizes, absence of randomized clinical trials, diverse follow-up periods, lack of control for some confounding factors, heterogeneous study designs and diverse clinical outcomes.

CONCLUSIONS

Although current evidence remains controversial, several factors have been associated with an impaired prognosis, which might allow clinicians to identify patients at higher risk for adverse clinical outcomes and find modifiable factors. Further research is needed to elucidate the impact of each risk factor in the mentioned outcomes.

Seasonality of hospitalization for schizophrenia and mood disorders: A single-center cross-sectional study in China

BACKGROUND

Seasonal patterns exist in many disorders and even serve as potential drivers of some disorders, but in schizophrenia and affective disorders, there is no uniform conclusion on the seasonal pattern.

METHODS

A total of 100,621 inpatients were surveyed in this study over 16 years, and 21,668 inpatients were ultimately included in the count after standard exclusion criteria were applied.

RESULTS

There was an uneven seasonal distribution of mental illness admissions (χ2 = 48.299, df = 18, P < .001). The peak of schizophrenia admissions occurred in the winter and the trough in the spring (52.6 % vs 50 %, P < .05). The peaks for depression and bipolar disorder were in the fall and spring, respectively, while the troughs were in the winter and fall, respectively (24.7 % vs 21.7 %, P < .05; 15.2 % vs 13.2 %, P < .05). Admissions for childhood mood disorders peaked in the fall (P < .05). We also found that the length of stay was also correlated with the season of admission, and that this seasonal fluctuation was not consistent across male and female populations.

LIMITATIONS

To avoid the effect of repeated hospitalizations, we maintained a registry of each patient's first admission only, which also resulted in our inability to explore the seasonal pattern of each disease recurrence at the individual level.

CONCLUSIONS

We found that the seasonal distribution of psychiatric admissions was not uniform. And there was also an uneven seasonal distribution of length of stay for patients admitted in different seasons. This may imply that certain environmental factors that vary with the seasons are potential drivers of mental illness.

Using Chronobiological Phenotypes to Address Heterogeneity in Bipolar Disorder

Bipolar disorder (BD) is a neuropsychiatric mood disorder characterized by recurrent episodes of mania and depression in addition to disruptions in sleep, energy, appetite, and cognitive functions-rhythmic behaviors that typically change on daily cycles. BD symptoms can also be provoked by seasonal changes, sleep, and/or circadian disruption, indicating that chronobiological factors linked to the circadian clock may be a common feature in the disorder. Research indicates that BD exists on a clinical spectrum, with distinct subtypes often intersecting with other psychiatric disorders. This heterogeneity has been a major challenge to BD research and contributes to problems in diagnostic stability and treatment outcomes. To address this heterogeneity, we propose that chronobiologically related biomarkers could be useful in classifying BD into objectively measurable phenotypes to establish better diagnoses, inform treatments, and perhaps lead to better clinical outcomes. Presently, we review the biological basis of circadian time keeping in humans, discuss the links of BD to the circadian clock, and pre-sent recent studies that evaluated chronobiological measures as a basis for establishing BD phenotypes. We conclude that chronobiology may inform future research using other novel techniques such as genomics, cell biology, and advanced behavioral analyses to establish new and more biologically based BD phenotypes.

Pharmacological Manipulation of the Circadian Clock: A Possible Approach to the Management of Bipolar Disorder

Bipolar disorder (BD) is a mood disorder with genetic and neurobiological underpinnings, characterized primarily by recurrent episodes of mania and depression, with notable disruptions in rhythmic behaviors such as sleep, energy, appetite and attention. The chronobiological links to BD are further supported by the effectiveness of various treatment modalities such as bright light, circadian phase advance, and mood-stabilizing drugs such as lithium that have effects on the circadian clock. Over the past 30 years, the neurobiology of the circadian clock has been exquisitely described and there now exists a detailed knowledge of key signaling pathways, neurotransmitters and signaling mechanisms that regulate various dimensions of circadian clock function. With this new wealth of information, it is becoming increasingly plausible that new drugs for BD could be made by targeting molecular elements of the circadian clock. However, circadian rhythms are multidimensional and complex, involving unique, time-dependent factors that are not typically considered in drug development. We review the organization of the circadian clock in the central nervous system and briefly summarize data implicating the circadian clock in BD. We then consider some of the unique aspects of the circadian clock as a drug target in BD, discuss key methodological considerations and evaluate some of the candidate clock pathways and systems that could serve as potential targets for novel mood stabilizers. We expect this work will serve as a roadmap to facilitate the development of compounds acting on the circadian clock for the treatment of BD.

Seasonality of hospital admissions for mental disorders in Hanoi, Vietnam

BACKGROUND

Some studies have shown a relationship between seasonality in weather patterns and depressive and behavioural disorders, especially in temperate climate regions. However, there is a lack of studies describing the seasonal patterns of hospital admissions for a variety of mental disorders in tropical and subtropical nations. The aim of this study has been to examine the relationship between seasons and daily hospital admissions for mental disorders in Hanoi, Vietnam.

DESIGNS

A 5-year database (2008-2012) compiled by Hanoi Mental Hospital covering mental disorder admissions diagnosed by the International Classification of Diseases 10 was analysed. A negative binominal regression model was applied to estimate the associations between seasonality and daily hospital admissions for mental disorders, for all causes and for specific diagnoses.

RESULTS

The summer season indicated the highest relative risk (RR=1.24, confidence interval (CI)=1.1-1.39) of hospital admission for mental disorders, with a peak in these cases in June (RR=1.46, CI=1.19-1.7). Compared to other demographic groups, males and the elderly (aged over 60 years) were more sensitive to seasonal risk changes. In the summer season, the RR of hospital visits among men increased by 26% (RR=1.26, CI=1.12-1.41) and among the elderly by 23% (RR=1.23, CI=1.03-1.48). Furthermore, when temperatures including minimum, mean, and maximum increased 1°C, the number of cases for mental disorders increased by 1.7%, 2%, and 2.1%, respectively.

CONCLUSION

The study results showed a correlation between hospital admission for mental disorders and season.

Identification of circadian gene variants in bipolar disorder in Latino populations

BACKGROUND

Variations in circadian genes can impact biological rhythms. Given the rhythm disturbances that characterize bipolar disorder (BD), genes encoding components of molecular clocks are good candidate genes for the illness.

METHODS

A family based association analysis of circadian gene single nucleotide polymorphisms (SNPs) and BD was conducted in Latino pedigrees. 884 individuals from 207 pedigrees (473BP phenotype and 411 unaffected family members) were genotyped. Family based single marker association testing was performed. Ancestral haplotypes (SNPs found to be in strong LD defined using confidence intervals) were also tested for association with BD.

RESULTS

Multiple suggestive associations between circadian gene SNPs and BD were noted. These included CSNK1E (rs1534891, p=0.00689), ARNTL (rs3789327, p=0.021172), CSNK1D (rs4510078, p=0.022801), CLOCK (rs17777927, p=0.031664). Individually, none of the SNPs were significantly associated with BD after correction for multiple testing. However, a 4-locus CSNK1E haplotype encompassing the rs1534891 SNP (Z-score=2.685, permuted p=0.0076) and a 3-locus haplotype in ARNTL (Z-score=3.269, permuted p=0.0011) showed a significant association with BD.

LIMITATIONS

Larger samples are required to confirm these findings and assess the relationship between circadian gene SNPs and BD in Latinos.

CONCLUSIONS

The results suggest that ARNTL and CSKN1E variants may be associated with BD. Further studies are warranted to assess the relationships between these genes and BD in Latino populations.

Psychiatric hospitalizations for affective disorders in Warsaw, Poland: Effect of season and intensity of sunlight

The purpose of this study was to assess any associations between the number of hospitalizations for affective disorders, seasons of the year and the intensity of sunlight in Poland, a country with a very changeable climate and significant seasonal fluctuations. We analyzed 2837 admissions with affective disorders hospitalized in the Institute of Psychiatry and Neurology in Warsaw, between 2002 and 2010 (mania, n=380, mixed episode, n=131, bipolar depression, n=736, recurrent depression, n=681, single depressive episode, n=909). For each diagnostic group admission time series were created and categorized into subgroups according to sex and age, and these were analyzed by means of the Autoregressive Integrated Moving Average (ARIMA) method. Regression models and correlations were used to assess the influence of the intensity of sunlight on the number of hospitalizations. Most mania admissions were noted in spring/summer months and in midwinter, mixed episode-late spring and winter, and depression (bipolar, recurrent and single depressive episode)-spring and autumn months. The association between frequency of admissions and monthly hours of sunshine was observed in some age and sex subgroups of patients with bipolar disorder and single depressive episode. The results support the seasonality of admissions of patients with affective disorders.

Investigating the mechanism(s) underlying switching between states in bipolar disorder

Bipolar disorder (BD) is a unique disorder that transcends domains of function since the same patient can exhibit depression or mania, states with polar opposite mood symptoms. During depression, people feel helplessness, reduced energy, and risk aversion, while with mania behaviors include grandiosity, increased energy, less sleep, and risk preference. The neural mechanism(s) underlying each state are gaining clarity, with catecholaminergic disruption seen during mania, and cholinergic dysfunction during depression. The fact that the same patient cycles/switches between these states is the defining characteristic of BD however. Of greater importance therefore, is the mechanism(s) underlying cycling from one state - and its associated neural changes - to another, considered the 'holy grail' of BD research. Herein, we review studies investigating triggers that induce switching to these states. By identifying such triggers, researchers can study neural mechanisms underlying each state and importantly how such mechanistic changes can occur in the same subject. Current animal models of this switch are also discussed, from submissive- and dominant-behaviors to kindling effects. Focus however, is placed on how seasonal changes can induce manic and depressive states in BD sufferers. Importantly, changing photoperiod lengths can induce local switches in neurotransmitter expression in normal animals, from increased catecholaminergic expression during periods of high activity, to increased somatostatin and corticotrophin releasing factor during periods of low activity. Identifying susceptibilities to this switch would enable the development of targeted animal models. From animal models, targeted treatments could be developed and tested that would minimize the likelihood of switching.

Genetics and epigenetics of circadian rhythms and their potential roles in neuropsychiatric disorders

Circadian rhythm alterations have been implicated in multiple neuropsychiatric disorders, particularly those of sleep, addiction, anxiety, and mood. Circadian rhythms are known to be maintained by a set of classic clock genes that form complex mutual and self-regulatory loops. While many other genes showing rhythmic expression have been identified by genome-wide studies, their roles in circadian regulation remain largely unknown. In attempts to directly connect circadian rhythms with neuropsychiatric disorders, genetic studies have identified gene mutations associated with several rare sleep disorders or sleep-related traits. Other than that, genetic studies of circadian genes in psychiatric disorders have had limited success. As an important mediator of environmental factors and regulators of circadian rhythms, the epigenetic system may hold the key to the etiology or pathology of psychiatric disorders, their subtypes or endophenotypes. Epigenomic regulation of the circadian system and the related changes have not been thoroughly explored in the context of neuropsychiatric disorders. We argue for systematic investigation of the circadian system, particularly epigenetic regulation, and its involvement in neuropsychiatric disorders to improve our understanding of human behavior and disease etiology.

Seasonality and bipolar disorder: a systematic review, from admission rates to seasonality of symptoms

INTRODUCTION

Bipolar disorder (BD) is a severe mental disorder affecting 1-4% of the population worldwide. It is characterized by periods of (hypo)manic and depressive episodes. Seasonal patterns (SP) may be observed in admission rates, mood relapses and symptom fluctuations.

METHODS

We conducted a systematic review of seasonality in BD, classifying studies based on seasonal admission rates to seasonality of symptoms assessments.

RESULTS

Fifty-one papers were identified of which 32 addressed hospitalization rates by season, 6 addressed categorical diagnoses, and 13 explored symptom dimensions. Seasonal peaks for different BD mood episodes are observed worldwide and widely replicated. Manic episodes peak during spring/summer and, to a lesser extent, in autumn, depressive episodes peak in early winter and, to a lesser extent, summer, and mixed episodes peak in early spring or mid/late summer. There was a high frequency of SP for manic episodes (15%) and depressive episodes (25%), the latter being associated with a more complex clinical profile (BD II subtype, comorbid eating disorders, more relapses and rapid cycling). Finally, there was evidence for greater seasonal fluctuations in mood and behavior in individuals with BD than in those with unipolar depression or 'healthy' controls.

LIMITATIONS

Sample size, gender distribution, methodological quality and sophistication of the analytical approaches employed varied considerably.

CONCLUSIONS

There is evidence of seasonality in BD, with emerging evidence that climatic conditions may trigger BD symptoms or episodes. A better understanding of the underlying mechanisms would facilitate the development of personalized chronobiological therapeutic and preventive strategies.

Seasonal variation of manic and depressive symptoms in bipolar disorder

OBJECTIVES

Analyses of seasonal variation of manic and depressive symptoms in bipolar disorder in retrospective studies examining admission data have yielded conflicting results. We examined seasonal variation of mood symptoms in a prospective cohort with long-term follow-up: the Collaborative Depression Study (CDS).

METHODS

The CDS included participants from five academic centers with a prospective diagnosis of bipolar I or II disorder. The sample was limited to those who were followed for at least 10 years of annual or semi-annual assessments. Time series analyses and autoregressive integrated moving average (ARIMA) models were used to assess seasonal patterns of manic and depressive symptoms.

RESULTS

A total of 314 individuals were analyzed (bipolar I disorder, n = 202; bipolar II disorder, n = 112), with both disorders exhibiting the lowest frequency of depressive symptoms in summer and the highest around the winter solstice, though the winter peak in symptoms was statistically significant only with bipolar I disorder. Variation of manic symptoms was more pronounced in bipolar II disorder, with a significant peak in hypomanic symptomatology in the months surrounding the fall equinox.

CONCLUSIONS

Significant seasonal variation exists in bipolar disorder, with manic/hypomanic symptoms peaking around the fall equinox and depressive symptoms peaking in the months surrounding the winter solstice in bipolar I disorder.

A genome-wide association study of seasonal pattern mania identifies NF1A as a possible susceptibility gene for bipolar disorder

OBJECTIVE

The use of subphenotypes may be an effective approach for genetic studies of complex diseases. Manic episodes with a seasonal pattern may distinguish phenotypic subgroups of bipolar subjects that may also differ genetically.

METHOD

We have performed a genome-wide association study using GAIN genotype data from the Bipolar Genome Study (BiGS) and bipolar subjects that were categorized as having either seasonal or non-seasonal patterned manic episodes.

RESULTS

A bipolar case-only analysis identified three genomic regions that differed between seasonal and non-seasonal patterned manic episodes of bipolar subjects. The most significant association was for rs41350144, which lies within an intron of NF1A gene on 1p31 (P=3.08×10(-7), OR=2.27). Haplotype construction using flanking three SNPs (rs41453448, rs1125777, and rs12568010) spanning 7549bp showed a more significant association (P=2.12×10(-7), OR=0.4).

CONCLUSIONS

These data suggest that genetic variants in the NF1A gene region may predispose to seasonal patterned of mania in bipolar disorder.

Impact of sunlight on the age of onset of bipolar disorder

OBJECTIVE

Although bipolar disorder has high heritability, the onset occurs during several decades of life, suggesting that social and environmental factors may have considerable influence on disease onset. This study examined the association between the age of onset and sunlight at the location of onset.

METHOD

Data were obtained from 2414 patients with a diagnosis of bipolar I disorder, according to DSM-IV criteria. Data were collected at 24 sites in 13 countries spanning latitudes 6.3 to 63.4 degrees from the equator, including data from both hemispheres. The age of onset and location of onset were obtained retrospectively, from patient records and/or direct interviews. Solar insolation data, or the amount of electromagnetic energy striking the surface of the earth, were obtained from the NASA Surface Meteorology and Solar Energy (SSE) database for each location of onset.

RESULTS

The larger the maximum monthly increase in solar insolation at the location of onset, the younger the age of onset (coefficient= -4.724, 95% CI: -8.124 to -1.323, p=0.006), controlling for each country's median age. The maximum monthly increase in solar insolation occurred in springtime. No relationships were found between the age of onset and latitude, yearly total solar insolation, and the maximum monthly decrease in solar insolation. The largest maximum monthly increases in solar insolation occurred in diverse environments, including Norway, arid areas in California, and Chile.

CONCLUSION

The large maximum monthly increase in sunlight in springtime may have an important influence on the onset of bipolar disorder.

Seasonal influences on admissions for mood disorders and schizophrenia in a teaching psychiatric hospital in Egypt

BACKGROUND

Distinct seasonal variation in hospital admission and various associations with the climatic parameters for mood disorders and schizophrenia have been previously reported in several world regions. There are, however, no North-African studies on this association.

METHODS

The charts of 1987 patients with mood disorders (mania 1181, depression 806) and 1359 patients with schizophrenia admitted from 2003 to 2007 from an university hospital at Mansoura, Egypt, were reviewed. Seasonality was assessed with Cosinor Analysis. Correlations of the rate of admissions for affective disorders and schizophrenia to climatic variables were performed, including lagged and differenced data.

RESULTS

There was a significant seasonal variation in the monthly admission frequencies both for mania (peak in June) and for depression (peak in December) but no significant seasonal variation was found in admissions with diagnosis of schizophrenia. The number of admissions for mania was positively correlated to indicators of temperature and luminosity, but inversely correlated to relative humidity. Quite the opposite, the number of admissions for depression showed a negative correlation to temperature and luminosity, but a positive correlation to relative humidity. 55-57% of the monthly variance of the number of admissions for mood disorders was explained by climatic variables.

CONCLUSIONS

Seasonality of admissions for mood disorders, but not for schizophrenia, has been demonstrated, in an African Mediterranean region with a fairly constant climate. The association between admission rates and climatic variables found in this study could pave the way for further studies aiming at exploration of the biological mechanism of this association as well as tailoring of treatment interventions on mood disorders.

Do symptoms of bipolar disorder exhibit seasonal variation? A multisite prospective investigation

OBJECTIVES

Evidence that symptoms of bipolar disorder (BD) vary seasonally is inconclusive. Here, a multisite prospective investigation of patients with BD was used to test the hypothesis that, on average, depressive symptoms peak in autumn/winter and hypo/manic symptoms peak in spring/summer. Secondary analyses explored gender and diagnosis [bipolar I disorder (BD-I) versus bipolar II disorder (BD-II)] effects on seasonality.

METHODS

A sample of 429 patients with BD (61.6% female; 56.2% BD-I) were recruited from 12 sites across Canada. Clinician-rated measures of manic [Young Mania Rating Scale (YMRS), n = 4,753 total observations] and depression symptoms [Montgomery-Åsberg Depression Rating Scale (MADRS), n = 4,691 observations] were taken at scheduled three-month visits as well as any unscheduled visits. At scheduled visits only, Hamilton Depression Rating Scale (Ham-D) assessments (n = 3,153 observations) were also made. Multi-level modeling (MLM) analyses were conducted separately for the three dependent variables and three definitions of Time: calendar month, nominal season, and harmonic analysis.

RESULTS

Primary analyses of the whole sample found that for manic symptoms (YMRS), neither calendar month nor nominal season were significant, and harmonic analyses found an unpredicted frequency two sinusoid, with peaks at 4th December and 4th June (p < 0.018). Secondary analyses found that this sinusoid approximately fit the YMRS data for females and those diagnosed with BD-II. For depression symptoms measured on the MADRS and Ham-D, no significant seasonal patterns were found in primary analyses of the whole sample. Secondary analyses found a significant increase in MADRS scores in November/December among females, but this pattern was not corroborated in nominal season or harmonic analyses.

CONCLUSIONS

No evidence of systematic seasonal variation in symptoms was found in the sample as a whole. Primary analyses found no evidence that hypo/manic symptoms peaked in the lighter months and depressive symptoms peaked in the darker months. The present findings align with broadly negative conclusions from three earlier prospective investigations, and provide the strongest evidence to date that seasonal changes do not in fact cause coordinated variation in BD symptoms.

The precipitants of manic/hypomanic episodes in the context of bipolar disorder: a review

BACKGROUND

Mania/hypomania is the hallmark feature of bipolar disorder. This paper aims to review the current evidence in relation to factors hypothesised to precipitate bipolar mania/hypomania, and suggest areas for future research.

METHODS

A selective review of original and review papers was conducted. The electronic databases 'PsycINFO' and 'PubMed' were searched using the following search strings: "bipolar disorder" or "mania" or "hypomania" or "manic-depression" with "triggers" or "precipitants" or "precedents" or "predictors".

RESULTS

There is evidence that goal attainment events, antidepressant medication, disrupted circadian rhythms, spring/summer seasonal conditions, and more tentatively, stressful life events and high emotional expression, may precipitate bipolar mania/hypomania in susceptible individuals. Evidence from case reports and clinical observations are also reported.

DISCUSSION

The pathways to bipolar mania/hypomania may be many and varied, and many of these pathways may be outside the awareness of individuals with bipolar disorder. Greater awareness of the broad number of precipitating factors is needed to inform self-management and psycho-educational programs to build resilience to further episodes. Future research is needed to explore what other factors may precipitate bipolar mania/hypomania, and to determine why some factors may precipitate mania/hypomania in some individuals with bipolar I or II disorder but not in others.

The role of environmental influences on schizophrenia admissions in Israel

OBJECTIVE

The role of environmental factors in hospitalization of patients with schizophrenia is incompletely understood. This study attempts to relate the pattern of hospital admissions to environmental variables such as season and to social factors such as nationally celebrated holidays.

METHODS

Charts of all adults (n = 4,331) with a discharge diagnosis of schizophrenia admitted to the Abarbanel Mental Health Centre (Bat Yam, Israel) between 1 January 2001 and 31 December 2005 were reviewed. Hospitalizations were classified by gender, first or repeat admission, month and season of admission, and whether or not the admission coincided with a major Jewish holiday period.

RESULTS

There was a significant reduction (p < 0.05) in first admissions for men during April, the month corresponding to Passover, the most widely celebrated holiday in Israel. This pattern was not seen for women or for repeat admissions. There was no significant effect of the season upon admission rates, using two different methods of defining the season.

CONCLUSIONS

This study demonstrated significant monthly variability in admission rates and a possible protective effect of a widely celebrated public religious holiday. A consistent effect of season upon rates of admission was not found. Future studies need to identify which specific social factors exert a protective or harmful effect and study how knowledge of these effects can be translated into clinical practice.

Lowering barometric pressure aggravates depression-like behavior in rats

Weather change has been known to influence the condition of patients with mood disorder. However, no animal studies have tested the influence of climatic factor on emotional impairment. In this study, we examined the effect of lowering barometric pressure (LP) in a climate-controlled room on immobility time in the forced swim test in rats, which is considered to be an index of behavioral despair (helplessness). When the rats were exposed to daily repeated forced swim, the immobility time gradually increased. This increment was inhibited by repeated administration of the antidepressant imipramine, suggesting that the immobility is an anxiety/depression-like behavior. LP exposure (20 hPa below the natural atmospheric pressure) further increased immobility time in rats submitted to repeated forced swim. In another series of experiments, we examined the effect of daily repeated LP exposure on the maintenance of immobility after withdrawal from 6-day repeated forced swim. When the rats were challenged with forced swim under natural atmospheric pressure on day 14 after the withdrawal, immobility time was significantly longer than in non-conditioned rats. These findings demonstrated that LP in the range of natural weather change augmented the depression-like behavior in rats.

Seasonal spring peaks of suicide in victims with and without prior history of hospitalization for mood disorders

BACKGROUND

Seasonal spring peaks of suicide are highly replicated, but their origin is poorly understood. As the peak of suicide in spring could be a consequence of decompensation of mood disorders in spring, we hypothesized that prior history of mood disorders is predictively associated with suicide in spring.

METHODS

We analyzed the monthly rates of suicide based upon all 37,987 suicide cases in the Danish Cause of Death Registry from 1970 to 2001. History of mood disorder was obtained from the Danish Psychiatric Central Register and socioeconomical data from the Integrated Database for Labour Market Research. The monthly rate ratio of suicide relative to December was estimated using a Poisson regression. Seasonality of suicide between individuals with versus without hospitalization for mood disorders was compared using conditional logistic regression analyses with adjustment for income, marital status, place of residence, and method of suicide.

RESULTS

A statistically significant spring peak in suicide was observed in both groups. A history of mood disorders was associated with an increased risk of suicide in spring (for males: RR=1.18, 95% CI 1.07-1.31; for females: RR=1.20, 95% CI 1.10-1.32).

LIMITATIONS

History of axis II disorders was not analyzed. Danish socioeconomical realities have only limited generalizability.

CONCLUSIONS

The results support the need to further investigate if exacerbation of mood disorders in spring triggers seasonal peaks of suicide. Identifying triggers for seasonal spring peaks in suicide may lead to uncovering novel risk factors and therapeutic targets for suicide prevention.

Seasonality of suicide in Sweden: relationship with psychiatric disorder

BACKGROUND

Little is known as to whether suicide seasonality is related to psychiatric disorders affecting suicide risk/incidence. The present study aims to assess suicide seasonality patterns with regard to the history of psychiatric morbidity among suicide victims.

METHODS

The history of psychiatric inpatient diagnoses in the five years prior to suicide was identified among all suicides in Sweden from 1992 to 2003. Suicide seasonality was estimated as the relative risk of suicide during the month of highest to that in the month of lowest suicide incidence. Analyses were performed with respect to sex, suicide method and history of inpatient treatment of psychiatric disorder.

RESULTS

Among both male (n=9,902) and female (n=4,128) suicide victims, there were peaks in suicide incidence in the spring/early summer. This seasonal variation was more evident in suicide victims with a psychiatric inpatient diagnosis than in those without such a diagnosis. A seasonal variation was found in most diagnostic groups, with significant peaks in males with a history of depression and in females with a history of a neurotic, stress-related, or somatoform disorder. Overall, suicide seasonality was more evident in violent than in non-violent suicide methods.

LIMITATION

Only psychiatric disorders severe enough to require hospital admission were studied.

CONCLUSION

A history of inpatient-treated psychiatric disorder appears to be associated with an increase in suicide seasonality, especially in violent suicide methods. This increase is found in several psychiatric disorders.

Relationship among latitude, climate, season and self-reported mood in bipolar disorder

OBJECTIVE

Many researchers have analyzed seasonal variation in hospital admissions for bipolar disorder with inconsistent results. We investigated if a seasonal pattern was present in daily self-reported daily mood ratings from patients living in five climate zones in the northern and southern hemispheres. We also investigated the influence of latitude and seasonal climate variables on mood.

METHOD

360 patients who were receiving treatment as usual recorded mood daily (59,422 total days of data). Both the percentage of days depressed and hypomanic/manic, and the episodes of depression and mania were determined. The observations were provided by patients from different geographic locations in North and South America, Europe and Australia. These data were analyzed for seasonality by climate zone using both a sinusoidal regression and the Gini index. Additionally, the influence of latitude and climate variables on mood was estimated using generalized linear models for each season and month.

RESULTS

No seasonality was found in any climate zone by either method. In spite of vastly different weather, neither latitude nor climate variables were associated with mood by season or month.

CONCLUSION

Daily self-reported mood ratings of most patients with bipolar disorder did not show a seasonal pattern. Neither climate nor latitude has a primary influence on the daily mood changes of most patients receiving medication for bipolar disorder.

Pure and mixed manic subtypes: a review of diagnostic classification and validation

OBJECTIVE

To review issues surrounding the diagnosis and validity of bipolar manic states.

METHODS

Studies of the manic syndrome and its diagnostic subtypes were reviewed emphasizing historical development, conceptualizations, formal diagnostic proposals, and validation.

RESULTS

Definitions delineating mixed and pure manic states derive some validity from external measures. DSM-IV and ICD-10 diagnosis of bipolar mixed states are too rigid and less restrictive definitions can be validated. Anxiety is a symptom often overlooked in diagnosis of manic subtypes and may be relevant to the mixed manic state. The boundary for separation of mixed mania and depression remains unclear. A 'pure' non-psychotic manic state similar to Kraepelin's 'hypomania' has been observed in several independent studies.

CONCLUSIONS

Issues surrounding diagnostic subtyping of manic states remain complex and the debates surrounding categorical versus dimensional approaches continue. To the extent that categorical approaches for mixed mania diagnosis are adopted, both DSM-IV and ICD-10 are too rigid. Inclusion of non-specific symptoms in definitions of mixed mania, such as psychomotor agitation, does not facilitate and may hinder the diagnostic separation of pure and mixed mania. The inclusion of a diagnostic seasonal specifier for DSM-IV, which is currently based on seasonal patterns for depression might be expanded to include seasonal patterns for mania. Boundaries between subtypes may be 'fuzzy' rather than crisp, and graded approaches could be considered. With the continued development of new tools, such as imaging and genetics, alternative approaches to diagnosis other than the purely symptom-centric paradigms might be considered.

Clinical and prognostic implications of seasonal pattern in bipolar disorder: a 10-year follow-up of 302 patients

BACKGROUND

More than 20% of bipolar patients may present with seasonal pattern (SP). Seasonality can alter the course of bipolar disorder. However, to date, long-term follow-up studies of bipolar patients presenting with SP are scarce. We present a 10-year follow-up study comparing clinical and demographic features of bipolar patients with and without SP.

METHOD

Three hundred and twenty-five bipolar I and II patients were followed up for at least 10 years. SP was defined according to DSM-IV criteria. Clinical variables were obtained from structured interviews with the patients and their relatives. Patients with and without SP were compared regarding clinical and sociodemographic variables and a stepwise logistic regression was performed.

RESULTS

Seventy-seven patients (25.5%) were classified as presenting with SP, while 225 (74.5%) were considered as presenting with no significant seasonal variation. Twenty-three patients (7%) were excluded from the study because it was unclear whether they had seasonality or not. There were no differences between groups regarding demographic variables. Patients with SP predominantly presented with bipolar II disorder, depressive onset, and depressive predominant polarity. The greater burden of depression did not correlate with indirect indicators of severity, such as suicidality, hospitalizations or psychotic symptoms.

CONCLUSIONS

Our study links the presence of SP with both bipolar II disorder and predominant depressive component. However, we could not find any difference regarding functionality or hospitalization rates. Modifications in the criteria to define SP are suggested for a better understanding of bipolar disorder.

The impact of environmental temperature on lithium serum levels

OBJECTIVES

Three studies have reported a seasonal variation in lithium serum levels, with higher levels during summer. Our objective was to investigate the impact of actual environmental temperature on lithium serum levels.

METHODS

A retrospective study was conducted using available records of lithium serum levels for the period between January 1995 and July 2004, obtained from three large teaching hospitals in The Netherlands. Lithium serum levels were linked to season and average daily temperature data obtained from the Royal Netherlands Meteorological Institute. An analysis was performed on all lithium serum levels not accounting for the intra-individual dependency of lithium serum levels. The association between season, temperature and both absolute lithium serum level and the frequency of potentially toxic serum levels was investigated. A mixed model analysis, accounting for intra-individual dependency of lithium serum levels, was performed.

RESULTS

A total of 41,102 lithium serum levels (3,054 patients) were included. A significant difference in mean lithium serum levels across seasons (p < 0.001) and temperature categories (p = 0.001) was found, peaking in summer [0.761 mmol/L, +/- standard error of the mean (SEM) 0.002] and at temperatures of 15-20 degrees C [0.762 mmol/L (+/- SEM 0.005)], and at a minimum in winter [0.748 mmol/L (+/- SEM 0.002)] and at <0 degrees C [0.741 mmol/L (+/- SEM 0.005)]. The relative frequency of potentially toxic serum levels significantly differed between seasons (p = 0.023, highest in winter), but not between temperature categories (p = 0.481). A significant positive association for intra-individual lithium serum level and season (p < 0.001) and temperature (p < 0.001) was established.

CONCLUSIONS

Season and environmental temperature have a statistically significant but therapeutically irrelevant effect on lithium serum levels.

Seasonal variations in bipolar disorder admissions and the association with climate: a population-based study

OBJECTIVE

Although seasonal influences on bipolar disorder admissions have long been observed, the issues of seasonality on different subtypes of mood episodes and the effects of associated climatic parameters remain controversial. This study sets out to examine seasonal variations in bipolar disorder admissions and the association with climate in Taiwan, a subtropical area with fairly constant weather conditions.

METHODS

This retrospective population-based study uses the Taiwan National Health Insurance Research Database for 1999-2003, identifying 15,060 admissions for bipolar disorder, comprising of 8631 manic, 2078 depressive and 4351 mixed/unspecified episodes. The auto-regressive integrated moving average model was applied to examine the presence of seasonality and the association with climate in each subtype of mood episodes.

RESULTS

Admission peaks were noted during spring/summer, early winter and early spring, for manic, depressive and mixed/unspecified episodes, respectively, while the associations with climatic parameters varied between the subtypes of mood episodes.

CONCLUSIONS

Seasonality in bipolar disorder does exist for all subtypes of mood episodes. The distinct seasonal patterns and various associations with the climatic parameters imply different underlying mechanisms for the onset of each subtype of mood episodes. The association between admission rates and certain climatic variables found in this study is informative and could pave the way for future studies aimed at exploring the influence of climate on the psychopathology of bipolar patients as well as the underlying mechanisms.

Seasonality of suicides with and without psychiatric illness in Denmark

This paper studied the seasonality of suicides among persons with and without psychiatric illness in Denmark from 1970 to 1999. A non-homogenous Poisson process was used to examine the data. The seasonality of suicides was shown to be associated with gender and their psychiatric histories with a declining trend of suicide incidence noted over the captured period. A mild seasonal component was reported in the period of the late 70s to early 80s (1975-1984) among females who did not have any psychiatric treatment history, while in the 80s the significant seasonality was mainly contributed by male suicides without a psychiatric history. Another mild possible invoked seasonality in the 90s was in males who suffered from psychiatric illness. The rest could be treated as random events. Apparently, the seasonality among suicides with psychiatric illness exists but its effect could vary in different periods of time and among genders in Denmark.

Seasonal influences on first-episode admission in affective and non-affective psychosis

BACKGROUND

Since bipolar affective disorder has been recorded, clinicians treating patients with this disorder have noted the cyclic nature of episodes, particularly an increase in mania in the spring and summer months and depression during winter.

OBJECTIVE

The aim of this study was to investigate seasonality in symptom onset and service admissions over a period of 10 years in a group of patients (n= 359) with first-episode (FE) mania (n= 133), FE schizoaffective disorder (n= 49) and FE schizophrenia (n= 177).

METHOD

Patients were recruited if they were between 15 and 28 years of age and if they resided in the geographical mental health service catchment area. The number of patients experiencing symptom onset and service admission over each month and season was recorded.

RESULTS

In terms of seasonality of time of service admission, the results indicate a high overall seasonality (particularly in men), which was observed in both the schizoaffective and the bipolar groups. In terms of seasonality of symptom onset, the results indicate that seasonality remains in the male bipolar group, but other groups have no seasonal trend.

CONCLUSIONS

This provides further evidence that systems mediating the entrainment of biological rhythms to the environment may be more pronounced in BPAD than in schizoaffective disorder and schizophrenia. These results may help facilitate the preparedness of mental heath services for patients at different times of the year.

Distinct seasonality of depressive episodes differentiates unipolar depressive patients with and without depressive mixed states

BACKGROUND

The bipolar nature of unipolar depression with depressive mixed states (DMX) needs further validation studies. The seasonality of depressive episodes is indicated to be different between unipolar and bipolar depressions. We therefore explored the seasonal pattern of depressive episodes in unipolar depressive patients with DMX.

METHODS

The subjects were 958 consecutive depressive inpatients for a 6-year period. For defining DMX, previously validated operational criteria were used (2 or more of 8 manic or mania-related symptoms: flight of idea, logorrhea, aggression, excessive social contact, increased drive, irritability, racing thoughts, and distractibility). Onsets of the index depressive episodes during each of the 12 calendar months were summed up over the 6-year for bipolar depressive patients (N = 95), and unipolar depressive patients with (N = 77) and without DMX (N = 786) separately. An appropriate statistic was used for testing seasonality.

RESULTS

A significant seasonal variation with a large peak in spring was recognized in unipolar depression without DMX, while both bipolar depression and unipolar depression with DMX had a significant fall peak. The monthly distribution of depressive episodes was significantly different between unipolar depression without DMX and other 2 diagnostic categories. Similar results were obtained in separate analyses for each gender.

LIMITATIONS

Further replication study using an epidemiological or outpatient sample is needed. Bipolar I and II patients were combined due to a small number of bipolar II patients in this sample.

CONCLUSION

Unipolar depression with DMX has a seasonal pattern similar to bipolar depression. The finding provides further evidence of the bipolar nature of unipolar depression with DMX.

Treatment of seasonal affective disorder: unipolar versus bipolar differences

Evidence-based treatments for seasonal affective disorder (SAD) include light therapy and pharmacotherapy. We briefly review the diagnosis and treatment of SAD, focusing on clinical and treatment differences between patients with unipolar and bipolar illness. Special considerations for the management of SAD in patients with bipolar disorder are discussed, including the need to monitor for emergence of manic and hypomanic mood switches, to use mood stabilizers in patients with bipolar I disorder, and to be aware of potential interactions between bright light and medications used in treating bipolar disorder. Chronobiological treatments such as bright light therapy may be combined with pharmacotherapy to enhance therapeutic effects, reduce adverse side effects, and optimize treatment in patients with seasonal and nonseasonal bipolar disorder.

Admission rates of bipolar depressed patients increase during spring/summer and correlate with maximal environmental temperature

OBJECTIVE

We intended to identify a relationship, if exists, between various climatic factors and the admission rates of bipolar affective disorder depressed patients (BPD) or major depressive disorder patients (unipolar) (UPD) to psychiatric hospitals, as well as potential seasonal variability in hospitalization rates of this population.

METHODS

Data on admissions of ICD-9 BPD and UPD patients to Tel Aviv's seven public psychiatric hospitals during 11 consecutive years were collected along with concomitant meteorological information

RESULTS

Admissions of 4117 patients with BPD and 1036 with UPD who fulfilled our specific inclusion criteria were recorded. Bipolar depressed, but not UPD, patients exhibited significant seasonal variation (higher spring and summer versus winter mean monthly admission rates), and the admission rates of patients with BPD, but not UPD, correlated significantly with mean maximal monthly environmental temperature

CONCLUSIONS

Increased environmental temperature may be a risk factor for evolvement of major depressive episode in patients with bipolar disorder with psychiatric co-morbidity, at least in cases that necessitate hospitalization and at the examined geographic/climatic region of Israel. Further large-scale studies with bipolar depressed patients with and without co-morbid disorders are needed to substantiate our findings and to determine the role of seasonal and climatic influence on this population, as well as its relationship to the pathophysiology of bipolar disorder.

Seasonal changes, sleep length and circadian preference among twins with bipolar disorder

BACKGROUND

We aimed at studying the seasonal changes in mood and behaviour, the distribution of hospital admissions by season, and the persistence of the circadian type in twins with bipolar disorder and their healthy co-twins.

METHODS

All Finnish like-sex twins born from 1940 to 1969 were screened for a diagnosis of bipolar type I disorder. The diagnosis was assessed with a structured research interview, and the study subjects (n = 67) filled in the Seasonal Pattern Assessment Questionnaire (SPAQ) and the Morningness-Eveningness Questionnaire (MEQ). For studying the persistence of the habitual sleep length and circadian type, we used data derived from the Finnish Twin Cohort Questionnaire (FTCQ). Bipolar twins were compared with their healthy co-twins.

RESULTS

Bipolar twins had greater seasonal changes in sleep length (p = 0.01) and mood (p = 0.01), and higher global seasonality scores (p = 0.03) as compared with their co-twins with no mental disorder. Sunny days (p = 0.03) had a greater positive effect on wellbeing in the bipolar than healthy co-twins.

CONCLUSIONS

Our results support the view that bipolar disorder is sensitive to the environmental influence in general and to the seasonal effect in specific. Exposure to natural light appears to have a substantial effect on wellbeing in twins with bipolar disorder.

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.

Effects of season and climate on the first manic episode of bipolar affective disorder in Korea

The purpose of this study was to determine if a seasonal pattern existed for the first manic episodes in Korea. The first manic episodes out of 152 bipolar disorder patients were investigated, in subjects who were admitted in two hospitals in Seoul between 1996 and 1999. Correlations between the monthly climate variables and the first monthly manic episodes indicated that the first manic episodes peaked in 25 cases during March. The mean monthly hours of sunshine and sunlight radiation correlated significantly with manic episodes. Separating the patients into two groups, namely, with and without major depressive episode, only the occurrence of manic episodes with major depressive episode was significantly correlated with mean monthly hours of sunshine. Separating the subjects by gender, the monthly first manic episodes was significantly correlated with the intensity of sunlight radiation in female patients only. These findings suggested that increasing the duration and intensity of sunlight could facilitate breakdown into the manic episodes.

Lack of association between seasonality and psychopathology in psychiatric outpatients

There exists an extensive literature documenting the impact of seasonality on rates of depression, atypical depression, bulimia, and suicide. In the present report drawn from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project, we reviewed the results of 1500 diagnostic evaluations of patients who presented to our psychiatric outpatient practice between 1995 and 2001. We sought to determine whether seasonal fluctuations in psychopathology were discernible at the level of how patients present for psychiatric treatment. Contrary to our hypotheses, we did not find (1) higher rates of onset of major depressive disorder in the spring and fall, (2) higher rates of depressive symptoms or rates of atypical depression in the winter, (3) higher rates of bulimia in the winter, or (4) higher rates of suicidal ideation in the spring. We conclude from these results that the association between seasonality and psychopathology may not be discernible at the level of presentations to an outpatient psychiatric practice.

Seasonal variation in suicides and in admissions to hospital for mania and depression

BACKGROUND

The influence of seasons on mood disorders is controversial.

OBJECTIVE

To examine monthly variations in admissions for mania and depressions including variations with sex and age and correlations with frequencies of suicides.

METHODS

All admissions for mania or depression (N=4341) in a population of 1,800,000 with 35,285 admissions in the years 1992-1996 were analysed. All 14,503 suicides in Norway the years 1969-1996 were also analysed.

RESULTS

Admissions for depression had a significant monthly variation for women (chi(2)=29.78, df=11, P<0.005) with the highest peak in November and for men (chi(2)=19.69, df=11, P<0.05) with the highest peak in April. Among women increasing age correlated negatively with the range of monthly observed/expected ratios (r(s)=-0.943, N=6, P<0.01) and with a of maximal monthly observed/expected ratio (r(s)=-0.943, N=6, P<0.01). Among men suicides correlated with admissions for depression (r=0.647, N=12, P<0.05) and mania (r=0.678, N=12, P<0.05).

LIMITATIONS

The time of admission to hospital are not identical to onset of affective episode. The study was done retrospectively. No sociocultural or physical environmental data were investigated.

CONCLUSION

A hypothesis of an influence of seasons on mood disorders is supported. Younger women seem to be especially vulnerable.

Seasonal variation of mixed and pure episodes of bipolar disorder

BACKGROUND

Although seasonal patterns of manic episodes have been reported, the seasonal variation of mixed states of bipolar disorder has received little attention. In the current report we address that concern as well as the overall seasonality of manic episodes.

METHODS

The seasonal pattern of 304 psychiatric hospital admissions for treatment of mixed or manic bipolar episodes over a 3-year period were analyzed employing two definitions of mixed manic states: DSM-III-R and an ROC derived definition.

RESULTS

The frequency of all manic episodes combined peaked in early spring, with a nadir in late fall. Pure manic admissions showed a similar pattern. Mixed manic admissions had a significantly different pattern, with a peak in late summer and a nadir in November. The differences between pure and mixed manic admissions were demonstrated with the use of the ROC definition for mixed states.

LIMITATIONS

Effects of medications and medication non-compliance may dampen natural seasonal patterns of episodes.

CONCLUSIONS

The different seasonal pattern of mixed and pure manic episodes support the separation of mixed episodes as a distinct clinical subtype.

Seasonality of manic depressive illness in Canada

OBJECTIVE

The objective of the study was to determine if a seasonal pattern existed for hospital admissions of manic depressive illness to a Ontario provincial psychiatric hospital.

METHOD

Admission records were reviewed for the 75 year period of the study. In the analysis factors including: mood state on admission, gender and the influence of psychotropic medications were considered.

RESULTS

For mania and depression there was no statistically significant seasonal pattern of admissions. For mixed state admissions peaked in the summer.

CONCLUSIONS

The results of this study contradict the seasonal pattern traditionally reported in the literature. The limitations of this study, which include changes in diagnostic criteria over time and admission date not identical to onset of affective episode, need to be acknowledged.

Seasonal influences on admissions for affective disorder and schizophrenia in Ireland: a comparison of first and readmissions

Although genetic and environmental factors operating before or around the time of birth have been demonstrated to be relevant to the aetiology of the major psychoses, a seasonal variation in the rates of admission of such patients has long been recognised. Few studies have compared first and readmissions. This study examined for seasonal variation of admission in the major psychoses, and compared diagnostic categories by admission status. Patients admitted to Irish psychiatric inpatient facilities between 1989 and 1994 with an ICD-9/10 diagnosis of schizophrenia or affective disorder were identified from the National Psychiatric Inpatient Reporting System (NPIRS). The data were analysed using a hierarchical log linear model, the chi-square test, a Kolmogorov-Smirnov (KS) type statistic, and the method of Walter and Elwood. The hierarchical log linear model demonstrated significant interactions between the month of admission and admission order (change in scaled deviance 28.77, df = 11, P < 0.003). Both first admissions with mania, and readmissions with bipolar affective disorder exhibited significant seasonality. In contrast, only first admissions with schizophrenia showed significant seasonal effects. Although first admissions with mania and readmissions with bipolar disorder both show seasonality, seasonal influences appear to be more relevant to onset of schizophrenia than subsequent relapse.

How effective is lithium in the prevention of relapse in bipolar disorder? A prospective naturalistic follow-up study

OBJECTIVE

The effectiveness of lithium in preventing recurrences of bipolar disorder was examined prospectively for 2 years in two representative samples of bipolar I patients being treated in a comprehensive program following recommended guidelines.

METHOD

One hundred and twenty patients were recruited from consecutive admissions to two catchment area psychiatric services (one in the United Kingdom, the other in New Zealand). They were seen at 3-monthly intervals by a member of the research team. Treatment was adjusted according to clinical needs.

RESULTS

Overall, two-thirds of the patients had a recurrence. Of the 57 on lithium as sole treatment, 39 (68%) had a further episode; 17 after stopping lithium. The 42 on other mood stabilisers and/or an antipsychotic, with or without lithium, did no better. By contrast, only eight (38%) of the 21 who were taking no prophylactic medication had a recurrence.

CONCLUSIONS

Lithium is much less effective in clinical practice than would be expected from clinical trial results. A major reason for this is poor compliance. Alternative treatment strategies are needed to improve the outcome for bipolar disorder patients.

Seasonal variation in bipolar disorder

BACKGROUND

In patients with bipolar disorder, admissions for manic and depressive episodes frequently display a seasonal pattern. We examined this variation and compared the patterns with the seasonal admission rates for schizophrenia.

METHOD

Patients with bipolar disorder or schizophrenia were identified from the Finnish Hospital Discharge Register of in-patient admissions to all psychiatric hospitals during the years 1969-91. They were included in the analysis if the first admission had occurred before 30 years of age. A total of 295 bipolar patients were found, and a sample of 295 schizophrenic patients was randomly selected for comparison.

RESULTS

There was no seasonal variation among all hospital admissions for bipolar disorder or schizophrenia. However, the first admission for a depressive compared with a manic episode of bipolar disorder occurred significantly more often in the autumn (33% v. 21% respectively). The peak difference occurred during the week after the autumnal equinox in September.

CONCLUSION

Our findings suggest that there is no seasonal variation in bipolar disorder, although in some patients the clinical course might be influenced by the autumn, as far as the likelihood of a first admission for depression is concerned.