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Two common approaches to identify subgroups of patients with bipolar disorder are clustering methodology (mixture analysis) based on the age of onset, and a birth cohort analysis. This study investigates if a birth cohort effect will influence the results of clustering on the age of onset, using a large, international database.
The database includes 4037 patients with a diagnosis of bipolar I disorder, previously collected at 36 collection sites in 23 countries. Generalized estimating equations (GEE) were used to adjust the data for country median age, and in some models, birth cohort. Model-based clustering (mixture analysis) was then performed on the age of onset data using the residuals. Clinical variables in subgroups were compared.
There was a strong birth cohort effect. Without adjusting for the birth cohort, three subgroups were found by clustering. After adjusting for the birth cohort or when considering only those born after 1959, two subgroups were found. With results of either two or three subgroups, the youngest subgroup was more likely to have a family history of mood disorders and a first episode with depressed polarity. However, without adjusting for birth cohort (three subgroups), family history and polarity of the first episode could not be distinguished between the middle and oldest subgroups.
These results using international data confirm prior findings using single country data, that there are subgroups of bipolar I disorder based on the age of onset, and that there is a birth cohort effect. Including the birth cohort adjustment altered the number and characteristics of subgroups detected when clustering by age of onset. Further investigation is needed to determine if combining both approaches will identify subgroups that are more useful for research.
Although suicidal behavior is very common in bipolar disorder (BD), few long-term studies have investigated incidence and risk factors of suicide attempts (SAs) specifically related to illness phases of BD.
We examined incidence of SAs during different phases of BD in a long-term prospective cohort of bipolar I (BD-I) and II (BD-II) patients and risk factors specifically for SAs during major depressive episodes (MDEs).
In the Jorvi bipolar study (JoBS), 191 BD-I and BD-II patients were followed using life-chart methodology. Prospective information on SAs of 177 patients (92.7%) during different illness phases was available up to five years. Incidence of SAs and their predictors were investigated using logistic and Poisson regression models. Analyses of risk factors for SAs occurring during MDEs were conducted using two-level random-intercept logistic regression models.
During the five-year follow-up, 90 SAs per 718 patient-years occurred. Compared with euthymia the incidence was highest, over 120-fold, during mixed states (765/1000 person-years [95% confidence interval (CI) 461–1269]) and also very high in MDEs, almost 60-fold (354/1000 [95%CI 277–451]). For risk of SAs during MDEs, the duration of MDEs, severity of depression and cluster C personality disorders were significant predictors.
In this long-term study, the highest incidences of SAs occurred in mixed phases and MDEs. The variations in incidence rates between euthymia and illness phases were remarkably large, suggesting that the question “when” rather than “who” may be more relevant for suicide risk in BD. However, risk during MDEs is likely also influenced by personality factors.
Disclosure of interest
The authors have not supplied their declaration of competing interest.
Probands with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for several psychiatric and neurodevelopmental disorders. The risk of these disorders among the siblings of probands has not been thoroughly assessed in a population-based cohort.
Every child born in Finland in 1991–2005 and diagnosed with ADHD in 1995–2011 were identified from national registers. Each case was matched with four controls on sex, place, and date of birth. The full siblings of the cases and controls were born in 1981–2007 and diagnosed in 1981–2013. In total, 7369 cases with 12 565 siblings and 23 181 controls with 42 753 siblings were included in the analyses conducted using generalized estimating equations.
44.2% of the cases and 22.2% of the controls had at least one sibling diagnosed with any psychiatric or neurodevelopmental disorder (risk ratio, RR = 2.1; 95% CI 2.0–2.2). The strongest associations were demonstrated for childhood-onset disorders including ADHD (RR = 5.7; 95% CI 5.1–6.3), conduct and oppositional disorders (RR = 4.0; 95% CI 3.5–4.5), autism spectrum disorders (RR = 3.9; 95% CI 3.3–4.6), other emotional and social interaction disorders (RR = 2.7; 95% CI 2.4–3.1), learning and coordination disorders (RR = 2.6; 95% CI 2.4–2.8), and intellectual disability (RR = 2.4; 95% CI 2.0–2.8). Also, bipolar disorder, unipolar mood disorders, schizophrenia spectrum disorders, other neurotic and personality disorders, substance abuse disorders, and anxiety disorders occurred at increased frequency among the siblings of cases.
The results offer potential utility for early identification of neurodevelopmental and psychiatric disorders in at-risk siblings of ADHD probands and also argue for more studies on common etiologies.
Adverse psychosocial working environments characterized by job strain (the combination of high demands and low control at work) are associated with an increased risk of depressive symptoms among employees, but evidence on clinically diagnosed depression is scarce. We examined job strain as a risk factor for clinical depression.
We identified published cohort studies from a systematic literature search in PubMed and PsycNET and obtained 14 cohort studies with unpublished individual-level data from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium. Summary estimates of the association were obtained using random-effects models. Individual-level data analyses were based on a pre-published study protocol.
We included six published studies with a total of 27 461 individuals and 914 incident cases of clinical depression. From unpublished datasets we included 120 221 individuals and 982 first episodes of hospital-treated clinical depression. Job strain was associated with an increased risk of clinical depression in both published [relative risk (RR) = 1.77, 95% confidence interval (CI) 1.47–2.13] and unpublished datasets (RR = 1.27, 95% CI 1.04–1.55). Further individual participant analyses showed a similar association across sociodemographic subgroups and after excluding individuals with baseline somatic disease. The association was unchanged when excluding individuals with baseline depressive symptoms (RR = 1.25, 95% CI 0.94–1.65), but attenuated on adjustment for a continuous depressive symptoms score (RR = 1.03, 95% CI 0.81–1.32).
Job strain may precipitate clinical depression among employees. Future intervention studies should test whether job strain is a modifiable risk factor for depression.
Whether temperament and character differ between bipolar disorder (BD) and major depressive disorder (MDD) patients and general population subjects, or between BD I and BD II patients, remains unclear.
BD patients (n=191) from the Jorvi Bipolar Study and MDD patients (n=266) from the Vantaa Depression Study (VDS) and the Vantaa Primary Care Depression Study were interviewed at baseline, at 6 and 18 months, and in the VDS at 5 years. A general population comparison group (n=264) was surveyed by mail. BD patients' scores on the Temperament and Character Inventory-Revised were compared at an index interview, when levels of depression and mania were lowest, with scores of MDD patients and controls. BD I (n=99) and BD II (n=92) patients were compared.
Compared with controls, both BD and MDD patients had higher harm avoidance [odds ratio (OR) 1.027, p<0.001 and OR 1.047, p<0.001, respectively] and lower persistence (OR 0.983, p=0.006 and OR 0.968, p<0.001, respectively) scores. Moreover, BD patients had lower self-directedness (OR 0.979, p=0.003), MDD patients lower reward dependence (OR 0.976, p=0.002) and self-transcendence (OR 0.966, p<0.001) scores. BD patients scored lower in harm avoidance (OR 0.980, p=0.002) and higher in novelty seeking (OR 1.027, p<0.001) and self-transcendence (OR 1.028, p<0.001) than MDD patients. No differences existed between BD I and II patients.
The patterns of temperament and character dimensions differed less between BD and MDD patients, than patients from their controls. The most pronounced difference was higher novelty seeking in BD than MDD patients. The dimensions investigated are unlikely to differ between BD I and BD II patients.
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