Time Trends in Lifetime Incidence Rates of First-Time Diagnosed Bipolar and Depressive Disorders Across 16 Years in Danish Psychiatric Hospitals

Abstract

Objective: There is conflicting evidence as to whether or not the incidences of affective disorders are on the rise. The aim of the present study was to identify time trends across 16 years in the incidences of affective disorders in a nationwide sample. Methods: Using the Danish Psychiatric Central Research Registry, age-and sexadjusted incidence rates of diagnosed affective disorders in Danish psychiatric hospitals using ICD-10 classification were calculated per 100,000 person-years for the population aged 4-65 years during the period 1995-2010. Results: Incidence rates of diagnosed bipolar disorder increased from 11.5 to 24.5, and there was an increase from 86.2 to 189.7 per 100,000 person-years for depression. Time trends were most pronounced for individuals up to 29 years of age. A sizeable part of the increase in incidence rates could be attributed to an increase in the total number of persons diagnosed in psychiatry. Conclusions: Time trends in incidence ratesshowed an increase for bipolar disorder and depressive disorders across 16 years, but found that some of the observed increase in incidence rates was related to a more widespread trend in Danish society of seeking and receiving psychiatric assistance.

Increase in diagnosis of depressive disorders contributes to the increase in antidepressant use in adolescents

“…Only a weak increase was observed in boys. This is in line with previous studies that have separately studied either diagnosed or self‐reported depression or prescription of ADs .…”

“…The incidence rate leveled out from 2013 and onwards. Increase in occurrence of depressive disorders among adolescents has also been reported in several other studies from Nordic countries .…”

“…It is, however, not straightforward to compare incidence rates across studies due to methodological differences such as use of different diagnostic manuals, differences in study populations and study periods, differences in organization and availability of health care services and/or level of health care services studied. In a study from Denmark, using the Danish Psychiatric Central Research Registry, the incidence rate of major depressive disorders in 2010 was reported to be 223.3 per 100 000 person years in 13–18 year olds . This is markedly lower than the incidence rate in the NPR in our study in 2010 (406 per 100 000 for the total adolescent population).…”

“…These factors may in turn have led to increased contact with the health services. Both the present study and the above‐mentioned Danish study showed an increase over time in the proportion of adolescents that were in contact with health services. Increased availability of mental health services may be part of the explanation .…”

Time trends in the incidence of diagnosed depression among people aged 5–25 years living in Finland 1995–2012

“…In a large UK study, based on primary care diagnoses of depression, the incidence per 1000 personyears among subjects aged 3-18 years were 2.2, 3.0 and 2.0 in 1995, 2002 and 2005, respectively [9]. There have been two register-based time-trend studies on the incidence or cumulative incidence of diagnosed depression in childhood and adolescence in the Nordic countries, one in Denmark and one in Finland [10,11]. The Finnish register-based study focused on birth cohorts born in 1987 and 1997 and it reported that the cumulative incidence of diagnosed unipolar depression and unspecified affective disorders increased during adolescence [11].…”