Purpose: Few population-based studies have examined the association between parental psychopathology and bipolar disorder (BPD) in offspring. One limitation is lack of control for potential confounding by indicators of parental socio-economic status or maternal smoking during pregnancy. Furthermore, none of them included analyses restricted to parental diagnoses received prior to the birth of the offspring. Associations could not be affected by child-related factors affecting the parent in such analyses. This study explores associations between those parental psychiatric disorders diagnosed at any point of time as well as those diagnosed before offspring birth, and BPD in offspring.
Methods: In this nested case-control study, we identified 1,861 cases, age up to 25 years, 3,643 matched controls, and their parents from Finnish national registers. The associations were examined using conditional logistic regression, calculating odds ratios (OR) and adjusting for region of birth, parental age and education and mother's smoking during pregnancy.
Results: Anytime diagnosed parental disorders associating with BPD in offspring (95% confidence interval) were BPD [OR (maternal) 5.2 (2.52-10.62); OR (paternal) 8.1 (3.77-17.26)], schizophrenia and related psychoses [OR (maternal) 3.1 (1.69-5.84); OR (paternal) 4.5 (1.97-10.27)], other affective disorders [OR (maternal) 3.0 (2.08-4.21); OR (paternal) 3.0 (1.97-4.47)] and maternal anxiety disorders OR 2.6 (1.08-6.42). Statistically significant associations were also found for parental schizophrenia and related psychoses, and other affective disorders, diagnosed before offspring birth.
Conclusions: BPD is associated with many parental psychiatric disorders, particularly BPD and schizophrenia and related psychoses. The associations must be partially due to child-independent factors. Covariate adjustments had only a minor impact on the associations.