Affective disorders are a set of psychiatric diseases characterized by abnormalities of emotional state. The main types of affective disorders are depression, bipolar disorder and anxiety disorder. These illnesses are disruptive for the individual and have social and economic effects such as functional impairment, disability or lost work productivity, and increased need of health services.

The numerous Danish National registers are a remarkable resource for epidemiological research because they include longitudinal data on the entire population of Denmark, including information on psychiatric diagnoses, other medical diagnoses, demographic information, income and labour market affiliation and other variables.

Researchers at NCRR have studied the epidemiology of affective disorders by utilizing and analysing data from the Danish National Registers. Unique data are used to investigate research questions that would be difficult or even impossible in other research samples; for example, the distribution of information and determinants of more rare outcomes in disorders such as bipolar disorders, and the long-term causes and outcomes of more common disorders such as depression.

Access to complete information on large and representative samples of persons with and without affective disorders allows for sound conclusions to be made from results. For example, a recent study documented that despite having the same diagnosis, patients with severe depression receive treatment of very different duration in the Danish psychiatric system. Another study of approximately one million Danish children showed that mothers’ use of antidepressants during pregnancy increases the risk of children being diagnosed with a psychiatric illness later in life.

Affective disorders are heritable to varying degrees, meaning that a portion of the risk for depression or bipolar disorder can be attributed to genetic factors. However, studies also show that a large proportion of the population-level variation in affective disorders is due to environmental factors such as early adversity and socioeconomic status. Current research focuses on gaining a better understanding of the relationships between genes, environment and affective disorders within the Danish population. This research is crucial for a better understanding of the etiology of affective disorders, and hopefully thereby improving prediction, prevention and treatment.

Currently, NCRR is involved in projects that examine questions like:

• To which extent does genetic risk affect the onset, course and outcome of affective disorders within the Danish population?
• How do early adverse life events interact with genetic risks associated with affective disorders?
• Do genes associated with increased risk of schizophrenia also predispose to affective disorders such as depression?  

For further reading:

Liu X., et al. (2017) ”Antidepressant use during pregnancy and psychiatric disorders in offspring: Danish nationwide register based cohort study.” British Medical Journal: https://doi.org/10.1136/bmj.j3668 

Liu X, et al (2017) ”Depression and Anxiety in the Postpartum Period and Risk of Bipolar Disorder: A Danish Nationwide Register-Based Cohort Study.” J Clin Psychiatry: 10.4088/JCP.16m10970

Musliner, K. L., et al (2017) ”Vascular pathology and trajectories of late-life major depressive disorder in secondary psychiatric care.” The American Journal of Geriatric Psychiatry: https://doi.org/10.1016/j.jagp.2017.07.006

Musliner, K., et al. (2017) “Progression from unipolar depression to schizophrenia.” Acta Psychiatrica Scandinavica: 10.1111/acps.12663

Musliner, K. L., et al (2016) ”Heterogeneity in 10-year course trajectories of moderate to severe major depressive disorder: A Danish national register-based study” JAMA Psychiatry: 10.1001/jamapsychiatry.20

Dahl, S. K., et al. (2016) “Early adversity and risk for moderate to severe unipolar depressive disorder in adolescence and adulthood: A register-based study of 978,647 individuals.” Journal of Affective Disorders: http://dx.doi.org/10.1016/j.jad.2017.03.014

Laursen, T. M., et al (2016) Mortality and life expectancy in persons with severe unipolar depression. Journal of Affective Disorders: 10.1016/j.jad.2015.12.067

Bergink, V., et al (2016) “Childhood adverse life events and parental psychopathology as risk factors for bipolar disorder.” Transl Psychiatry: 10.1038/tp.2016.201

Musliner, K., et al. (2015) Parental history of psychiatric diagnoses and unipolar depression: a Danish National Register-based cohort study. Psychological Medicine:  10.1017/S0033291715000744

Mortensen, P. B., et al. (2011). "Neonatal antibodies to infectious agents and risk of bipolar disorder: a population-based case-control study." Bipolar Disord: 10.1111/j.1399-5618.2011.00962.x