Psychiatric disorders and mortality due to external causes following diagnosis of endometriosis at a young age: a longitudinal register-based cohort study in Finland.

ABSTRACT

BACKGROUND: Endometriosis diagnosed in adults is associated with increased risk of various psychiatric disorders. However, little is known concerning psychiatric comorbidity and mortality due to external causes associated with endometriosis diagnosed at a young age. OBJECTIVE: This longitudinal cohort study aimed to investigate the link between surgical diagnosis of endometriosis at a young age and subsequent psychiatric disorders and mortality due to external causes. In addition, we compared the occurrence of the most common psychiatric disorders between different sites of surgically confirmed endometriosis (ovarian vs other) because of possible differences in pain manifestations. STUDY DESIGN: We conducted a retrospective register-based cohort study. Altogether 4532 women with surgically confirmed diagnosis of endometriosis before the age of 25 years from 1987 to 2012 were identified from the Finnish Hospital Discharge Register. They were matched with women without surgically diagnosed endometriosis for age and municipality on the index day (n=9014). Women were followed up from the index day until the end of 2019 for the outcomes of interest, which included 9 groups of psychiatric disorders (inpatient episodes since 1987, outpatient episodes since 1998) and death due to external causes, including deaths due to accidents, suicides, and violence (Finnish Register of Causes of Death). Cox proportional hazard models were applied to assess the crude and parity-adjusted hazard ratios and 95% confidence intervals. RESULTS: The cohort's median age was 22.9 years (interquartile range, 21.3-24.1) at the beginning and 42.5 years (36.7-48.3) after a median follow-up time of 20.0 years (14.5-25.7). We observed a higher hazard of depressive, anxiety, and bipolar disorders in women with endometriosis compared with the reference cohort, with depressive and anxiety disorders being the two most common psychiatric disorders. These differences appeared early and remained the same during the entire follow-up, irrespective of whether assessed from the data on inpatient episodes only or the data on both in- and outpatient episodes. The corresponding adjusted hazard ratios were 2.57 (95% confidence interval, 2.11-3.14) and 1.87 (1.65-2.12) for depressive disorders, 2.40 (1.81-3.17) and 2.09 (1.84-2.37) for anxiety disorders, and 1.71 (1.30-2.26) and 1.66 (1.28-2.15) for bipolar disorders, respectively. A higher hazard was observed for nonorganic sleeping disorders for the first 10 years only (3.83; 2.01-7.30) when assessed using the data on both in- and outpatient episodes. When based on inpatient records, a higher hazard for alcohol/drug dependence after 15 years of follow-up (2.07; 1.21-3.54) was observed. The difference in hazard for personality disorders tended to increase during follow-up (<10 years, 2.12 [1.28-3.52]; ≥10 years, 3.08 [1.44-6.57]). Depressive and anxiety disorders occurred more frequently in women with types of endometriosis other than ovarian endometriosis. No difference in deaths due to external causes was observed between the endometriosis and reference cohorts. CONCLUSION: Surgical diagnosis of endometriosis at a young age was associated with increased incidence of several psychiatric disorders. Moreover, within the endometriosis population, psychiatric comorbidity was more common in women with types of endometriosis other than ovarian endometriosis. We speculate that chronic pain is essential in the development of these psychiatric disorders, and that early and effective pain management is important in reducing the risk of psychiatric morbidity in young women. More research concerning the associations and management of endometriosis and associated psychiatric disorders is warranted.