The nosological status of unipolar mania and hypomania within UK Biobank according to objective and subjective measures of diurnal rest and activity

An epidemiological study of season of birth, mental health, and neuroimaging in the UK Biobank

Environmental exposures during the perinatal period are known to have a long-term effect on adult physical and mental health. One such influential environmental exposure is the time of year of birth which affects the amount of daylight, nutrients, and viral load that an individual is exposed to within this key developmental period. Here, we investigate associations between season of birth (seasonality), four mental health traits (n = 137,588) and multi-modal neuroimaging measures (n = 33,212) within the UK Biobank. Summer births were associated with probable recurrent Major Depressive Disorder (β = 0.026, pcorr = 0.028) and greater mean cortical thickness in temporal and occipital lobes (β = 0.013 to 0.014, pcorr<0.05). Winter births were associated with greater white matter integrity globally, in the association fibers, thalamic radiations, and six individual tracts (β = -0.013 to -0.022, pcorr<0.05). Results of sensitivity analyses adjusting for birth weight were similar, with an additional association between winter birth and white matter microstructure in the forceps minor and between summer births, greater cingulate thickness and amygdala volume. Further analyses revealed associations between probable depressive phenotypes and a range of neuroimaging measures but a paucity of interactions with seasonality. Our results suggest that seasonality of birth may affect later-life brain structure and play a role in lifetime recurrent Major Depressive Disorder. Due to the small effect sizes observed, and the lack of associations with other mental health traits, further research is required to validate birth season effects in the context of different latitudes, and by co-examining genetic and epigenetic measures to reveal informative biological pathways.

The Diagnostic Concept of Unipolar Mania: The Missing Entity of the Affective Spectrum

ABSTRACT

Although the traditional nosological view interprets mania as strictly connected with depression in the context of manic-depressive illness, unipolar mania (UM), that is, the lifetime occurrence of mania or hypomania in the absence of depression, has been proposed as a necessary diagnostic entity. Epidemiological data estimate that at least 5% of people with type I bipolar disorder never experienced depression. These subjects are more often males with a hyperthymic temperament, a younger age at onset, and more psychotic features. Current classification systems do not formally recognize UM, but different definitions of mania without depression have been proposed. UM should be assessed according to the number of mood episodes, the predominance of manic or hypomanic episodes, and its clinical course. More generally, UM should be considered in the context of an affective spectrum including different clinical phenotypes based on the predominance of depressive or manic symptoms. Additional clinical and epidemiological research in this field is needed.

Characterizing the clinical profile of mania without major depressive episodes: a systematic review and meta-analysis of factors associated with unipolar mania

BACKGROUND

The diagnostic concept of unipolar mania (UM), i.e. the lifetime occurrence of mania without major depressive episodes, remains a topic of debate despite the evidence accumulated in the last few years. We carried out a systematic review and meta-analysis of observational studies testing factors associated with UM as compared to bipolar disorder with a manic-depressive course (md-BD).

METHODS

Studies indexed up to July 2022 in main electronic databases were searched. Random-effects meta-analyses of the association between UM and relevant correlates yielded odds ratio (OR) or standardized mean difference (SMD), with 95% confidence intervals (CIs).

RESULTS

Based on data from 21 studies, factors positively or negatively associated with UM, as compared to md-BD, were: male gender (OR 1.47; 95% CI 1.11-1.94); age at onset (SMD -0.25; 95% CI -0.46 to -0.04); number of hospitalizations (SMD 0.53; 95% CI 0.21-0.84); family history of depression (OR 0.55; 95% CI 0.36-0.85); suicide attempts (OR 0.25; 95% CI 0.19-0.34); comorbid anxiety disorders (OR 0.35; 95% CI 0.26-0.49); psychotic features (OR 2.16; 95% CI 1.55-3.00); hyperthymic temperament (OR 1.99; 95% CI 1.17-3.40). The quality of evidence for the association with previous suicide attempts was high, moderate for anxiety disorders and psychotic features, and low or very low for other correlates.

CONCLUSIONS

Despite the heterogeneous quality of evidence, this work supports the hypothesis that UM might represent a distinctive diagnostic construct, with peculiar clinical correlates. Additional research is needed to better differentiate UM in the context of affective disorders, favouring personalized care approaches.

Prevalence and characteristics of unipolar mania in a low-income country setting: population-based data from the Butajira cohort, rural Ethiopia

PURPOSE

Previous research suggests unipolar mania, i.e., bipolar disorder without depression, to be more common in low-income countries. However, longitudinal population-based studies on unipolar mania from low-income countries are lacking. This study therefore examined unipolar mania, in Butajira, Ethiopia, and associations with possible determinants.

METHODS

Key informants and 68,378 screenings with the Composite International Diagnostic Interviews (CIDI 2.1) identified suspected cases of bipolar disorder. Diagnosis was confirmed using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN 2.1) (n = 2,285). 315 participants with bipolar disorder were recruited and followed up for an average of 2.5 years. Unipolar mania was defined when illness episodes consisted of at least two manic relapses. 240 cases had sufficient data to ascertain course of disorder.

RESULTS

41.7% (100 of 240 cases) of participants had unipolar mania. Unipolar mania was associated with less suicidal ideation (0% vs. 26.4%, p < 0.001), less suicidal thoughts (occasionally/often: 1%/3% vs. 19.6%/21%, p < 0.001), and less history of suicide attempt (2% vs. 11.6%, p = 0.01). The participants with unipolar mania tended to have better social functioning (OR = 2.05, p = 0.07) and less alcohol use (20.8% vs. 31.4%, p = 0.07). The study was partly based on retrospective data liable to recall bias. Some cases defined as unipolar mania in our study may later develop depression.

CONCLUSION

Previous cross-sectional studies finding high proportions of unipolar mania in low-income countries appear supported. Unipolar mania trended towards better social functioning and was associated with lower suicidality. Future unipolar mania specifications could inform treatment and prognostic estimates of bipolar disorder.