Parental history of psychiatric diagnoses and unipolar depression: a Danish National Register-based cohort study.
BACKGROUND
Depression is known to run in families, but the effects of parental history of other psychiatric diagnoses on depression rates are less well studied. Few studies have examined the impact of parental psychopathology on depression rates in older age groups.


METHODS
We established a population-based cohort including all individuals born in Denmark after 1954 and alive on their 10th birthday (N = 29 76 264). Exposure variables were maternal and paternal history of schizophrenia, bipolar disorder, depression, anxiety or 'other' psychiatric diagnoses. Incidence rate ratios (IRRs) were estimated using Poisson regressions.


RESULTS
Parental history of any psychiatric diagnosis increased incidence rates of outpatient (maternal: IRR 1.88, p < 0.0001; paternal: IRR 1.68, p < 0.0001) and inpatient (maternal: IRR 1.99, p < 0.0001; paternal: IRR 1.83, p < 0.0001) depression relative to no parental history. IRRs for parental history of non-affective disorders remained relatively stable across age groups, while IRRs for parental affective disorders (unipolar or bipolar) decreased with age from 2.29-3.96 in the youngest age group to 1.53-1.90 in the oldest group. IRR estimates for all parental diagnoses were similar among individuals aged ⩾41 years (IRR range 1.51-1.90).


CONCLUSIONS
Parental history of any psychiatric diagnosis is associated with increased incidence rates of unipolar depression. In younger age groups, parental history of affective diagnoses is more strongly associated with rates of unipolar depression than non-affective diagnoses; however, this distinction disappears after age 40, suggesting that parental psychopathology in general, rather than any one disorder, confers risk for depression in middle life.
Department of Mental Health,Johns Hopkins Bloomberg School of Public Health,Baltimore,MD,USA.
K L
KL
Musliner
National Centre for Register-based Research,University of Aarhus,Aarhus,Denmark and The Lundbeck Foundation Initiative for Integrative Psychiatric Research,iPSYCH,Denmark.
B B
BB
Trabjerg
National Centre for Register-based Research,University of Aarhus,Aarhus,Denmark and The Lundbeck Foundation Initiative for Integrative Psychiatric Research,iPSYCH,Denmark.
B L
BL
Waltoft
National Centre for Register-based Research,University of Aarhus,Aarhus,Denmark and The Lundbeck Foundation Initiative for Integrative Psychiatric Research,iPSYCH,Denmark.
T M
TM
Laursen
National Centre for Register-based Research,University of Aarhus,Aarhus,Denmark and The Lundbeck Foundation Initiative for Integrative Psychiatric Research,iPSYCH,Denmark.
P B
PB
Mortensen
Department of Mental Health,Johns Hopkins Bloomberg School of Public Health,Baltimore,MD,USA.
P P
PP
Zandi
National Centre for Register-based Research,University of Aarhus,Aarhus,Denmark and The Lundbeck Foundation Initiative for Integrative Psychiatric Research,iPSYCH,Denmark.
T
T
Munk-Olsen
D000328:Adult; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D003863:Depression / Q000175:diagnosis* / Q000453:epidemiology*; D003866:Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010290:Parents / Q000523:psychology*; D011569:Psychiatric Status Rating Scales; D012042:Registries; D012720:Severity of Illness Index; D016019:Survival Analysis; D055815:Young Adult
Parental history; register-based research; survival analysis; unipolar depression