Seasonality of births in affective disorder in an Irish population

Perinatal photoperiod associations with bipolar disorder and depression: A systematic literature review and cross-sectional analysis of the UK Biobank database

Season-of-birth associations with psychiatric disorders point to environmental (co-)aetiological factors such as natural photoperiod that, if clarified, may allow interventions toward prevention. We systematically reviewed the literature concerning season-of-birth and bipolar disorder and depression and explored associations between the perinatal natural photoperiod and these outcomes in a cross-sectional analysis of the UK Biobank database. We used mean daily photoperiod and relative photoperiod range (relative to the mean) in the 3rd trimester and, separately, in the first 3 months post birth as metrics. From review, increased risk of depression with late spring birth is compatible with increased odds of probable single episode-, probable recurrent-, and diagnosed depression (OR 2.85 95 %CI 1.6-5.08, OR 2.20 95 %CI 1.57-3.1, and OR 1.48 95 %CI 1.11-1.97, respectively) with increasing 3rd trimester relative photoperiod range for participants who experienced relatively non-extreme daily photoperiods. Risk of bipolar disorder with winter-spring birth contrasted with no consistent patterns of perinatal photoperiod metric associations with bipolar disorder in the UK Biobank. As natural photoperiod varies by both time-of-year and latitude, perinatal natural photoperiods (and a hypothesized mechanism of action via the circadian timing system and/or serotonergic circuitry associated with the dorsal raphe nucleus) may reconcile inconsistencies in season-of-birth associations. Further studies are warranted.

Short-active photoperiod gestation induces psychiatry-relevant behavior in healthy mice but a resiliency to such effects are seen in mice with reduced dopamine transporter expression

A higher incidence of multiple psychiatric disorders occurs in people born in late winter/early spring. Reduced light exposure/activity level impacts adult rodent behavior and neural mechanisms, yet few studies have investigated such light exposure on gestating fetuses. A dysfunctional dopamine system is implicated in most psychiatric disorders, and genetic polymorphisms reducing expression of the dopamine transporter (DAT) are associated with some conditions. Furthermore, adult mice with reduced DAT expression (DAT-HT) were hypersensitive to short active (SA; 19:5 L:D) photoperiod exposure versus their wildtype (WT) littermates. Effects of SA photoperiod exposure during gestation in these mice have not been examined. We confirmed adult females exhibit a heightened corticosterone response when in SA photoperiod. We then tested DAT-HT mice and WT littermates in psychiatry-relevant behavioral tests after SA or normal active (NA; 12:12 L:D) photoperiod exposure during gestation and early life. SA-born WT mice exhibited sensorimotor gating deficits (males), increased reward preference, less immobility, open arm avoidance (females), less motivation to obtain a reward, and reversal learning deficits, vs. NA-born WT mice. DAT-HT mice were largely resilient to these effects, however. Future studies will determine the mechanism(s) by which SA photoperiod exposure influences brain development to predispose toward emergence of psychiatry-relevant behaviors.

Season of birth and mood seasonality in late childhood and adolescence

A significant season of birth effect on mood seasonality has been detected in young adults, with higher sensitivity to seasonal changes for people born during spring or summer months (long photoperiod) than those born during autumn or winter months (short photoperiod). The aim of this study was to verify whether the birth season effect on mood seasonality is already present in late childhood and adolescence. To this end, the Seasonal Pattern Assessment Questionnaire for Children and Adolescents (SPAQ-CA) was administered to 1523 Italian participants (870 females, 653 males), ranging from 10 to 17 years of age. The Global Seasonality Score (GSS) was computed as a measure of mood seasonality. Analysis of covariance showed a significant season of birth effect on GSS; although no comparisons were significant when Tukey's posthoc test for unequal samples was performed, it was observed that adolescents born in summer achieved the highest scores while those born in winter obtained the lowest. The present data point out that a significant season of birth effect on mood seasonality is already present in late childhood and adolescence.

Risk factors in relation to an emergence of bipolar disorder: a systematic review

OBJECTIVE

There is a consensus that genetic factors are important in the causation of bipolar disorder (BPD); however, little is known about other risk factors in the aetiology of BPD. Our aim was to review the literature on such risk factors - risk factors other than family history of affective disorders - as predictors for the initial onset of BPD.

METHODS

We conducted a literature search using the MEDLINE, PsycINFO and EMBASE databases. We selected factors of interest including demographic factors, factors related to birth, personal, social and family backgrounds, and history of medical conditions. The relevant studies were extracted systematically according to a search protocol.

RESULTS

We identified approximately 100 studies that addressed the associations between antecedent environmental factors and a later risk for BPD. Suggestive findings have been provided regarding pregnancy and obstetric complications, winter-spring birth, stressful life events, traumatic brain injuries and multiple sclerosis. However, evidence is still inconclusive. Childbirth is likely to be a risk factor. The inconsistency across studies and methodological issues inherent in the study designs are also discussed.

CONCLUSION

Owing to a paucity of studies and methodological issues, risk factors of BPD other than family history of affective disorders have generally been neither confirmed nor excluded. We call for further research.

Use of statistical techniques in studies of suicide seasonality, 1970 to 1997

The effect of seasons on suicides has been suggested repeatedly. In order to reveal a true seasonal pattern, an appropriate statistical technique, which is sensitive to a specific type of cyclic variation in the data, must be chosen. This study is a review of the use of statistical techniques for seasonality and of some important characteristics of study samples that were evaluated from 46 original suicide seasonality articles published in major psychiatric journals. The results showed that statistical techniques were applied in a majority of articles, but they were commonly lacking regarding analyses, which compared seasonal patterns among subgroups of a population. In recent studies more sophisticated statistical techniques were utilized for seasonality, like spectral analyses, as compared with earlier studies, in which the emphasis was on chi-square tests. Lack of reporting essential features of the data, such as the sample size and monthly values of suicides, were frequent. The calendar effect was adjusted only in 11 studies. Some recommendations concerning the methodological and reporting issues are summarized for future articles on the seasonal affect on suicides.

The trajectory of suicidal behavior over time

Some empirical work on genetic and prenatal factors in suicidality is presented. These factors may represent enduring predispositions that comprise risk for initial as well as later suicidal behavior. The existence of enduring predispositions does not preclude the possibility, however, that initial suicidal behavior sets processes into motion that spur later suicidal behavior. Based on past conceptual and empirical work, I suggest two psychological processes--cognitive sensitization and opponent processes--that may partly explain the link between past and future suicidal behavior.

Birth month and suicidal and depressive symptoms in Australians born in the Southern vs. the Northern hemisphere

To test whether Australians in utero during the Southern hemisphere flu peak would show increased suicidal and depressive symptoms, as would those born in the Northern hemisphere and who were in utero during the Northern hemisphere flu peak. A sample of 2514 adolescents and young adults presenting to general practitioners completed measures of depressive and suicidal symptoms. Patients' date and country of birth were recorded. Those born in the Southern hemisphere in September-November showed the highest suicidal and depressive symptoms, as did those born in the Northern hemisphere in March-May. Season of birth may be a risk factor for depressive and suicidal symptoms.

Epidemiological comparison of schizophrenia and bipolar disorder

Schizophrenia and bipolar disorder share many epidemiological features in common, but there are also differences. Both disorders share some risk factors, suggesting etiological antecedents that date to the perinatal period; these include excess of winter-spring births, abnormal dermatoglyphics, and probably an excess of perinatal complications. By contrast, an excess of urban births and an excess of minor physical anomalies are present in schizophrenia, but apparently not in bipolar disorder. Bipolar disorder also may be found in geographic, presumably genetic, isolates and in higher prevalence in higher socio-economic groups, which also differentiates it from schizophrenia. It is hypothesized that a subset of individuals with bipolar disorder constitutes a distinct disease entity, but that the majority share some common etiological antecedents with schizophrenia and may represent a disease continuum.