ELEVATED RISK FOR SPECIALISED PSYCHIATRIC CARE DUE TO DEPRESSION OR ANXIETY, BUT NOT FOR SUICIDE, IN A SCANDINAVIAN COHORT OF PATIENTS DIAGNOSED WITH PSORIATIC ARTHRITIS.

Background:
Depression and anxiety are more common in patients with psoriatic arthritis (PsA) than in the general population according to previous studies, not least based on questionnaire surveys also capturing milder forms of these conditions. Whether this is also true for more severe forms of depression or anxiety, requiring specialised psychiatric care, remains unknown. Furthermore, there is a paucity of data on suicidality in PsA, with available studies showing conflicting results [1, 2].
Objectives:
To study the incidence of depression or anxiety, diagnosed in specialised psychiatric care, and death by suicide, in a cohort of patients with PsA followed from the time of diagnosis.
Methods:
Using Clinical Rheumatology Registers linked with National Patient Registers, we identified newly-diagnosed PsA patients (≥18 years old) in Denmark (DK) (2003-2017) and Sweden (SE) (2007-2021). Through linkages with population registers, each patient was matched at the PsA diagnosis date (=index date) by sex, age and region with 10 (DK) or 5 (SE) general population comparator-subjects. We excluded all patients/comparator-subjects with a history of depression or anxiety prior to the index date, based on ICD-10 codes or filled prescriptions (ATC codes) for drugs for depression/anxiety, or with prior diagnoses of other arthritic diseases. To ascertain capture of this information, all included individuals were required to have resided in the country (SE or DK, respectively) for at least three years prior to index date. We defined the following three outcomes: 1) a main ICD-10 diagnosis of depression (F32-F34, F38-F39) or anxiety (F40-F42) from specialised psychiatric out- or inpatient care; 2) the same, but limited to inpatient care diagnoses only; 3) death by suicide (data only available from the Swedish Cause of Death Register). Participants were followed from the index date to the earliest of the outcome under investigation, emigration, death from any cause, or end of the study assessment period (2018/2022 for DK/SE). Incidences of each outcome in patients vs. their comparator-subjects were assessed through Cox regression, separately for SE and DK and stratified by age, sex and calendar year. Results from both countries were meta-analysed with a random effects model. Analyses on subgroups (male vs. female, calendar periods) were also performed, as were analyses additionally adjusted for education (as socioeconomic proxy; only available in SE data).
Results:
During the case identification periods, 1,964 and 21,719 newly-diagnosed PsA patients were identified in DK and SE, respectively. Similar proportions of patients and comparator-subjects had a history of depression or anxiety (13%/9% of patients/comparator-subjects in DK, and 23%/23% in SE) and were excluded. The final cohort contained 1,685 patients with PsA from DK and 16,321 from SE. Numerically, all comorbidities were slightly more frequent in PsA than in the comparator-subjects (Table 1). Through the assessment periods, we observed a total of 430 events (Outcome 1; in- or outpatient care), 86 events (Outcome 2; inpatient care), and 16 deaths from suicide (Outcome 3, in SE only) in the PsA groups. Compared to the general population, we found that the incidence of depression or anxiety in specialised psychiatric out- or inpatient care (Outcome 1) was elevated in PsA patients, hazard ratio = 1.39 (95% confidence interval 1.20-1.61). The risk of inpatient care due to depression or anxiety (Outcome 2) was numerically slightly higher in PsA, without reaching statistical significance. No increased risk was observed for death by suicide (Outcome 3; Figure 1). Analyses by subgroups did not show strong differences between men and women, nor in different calendar periods. Additional adjustment for education (in SE data only) did not substantially modify the hazard ratios.
Conclusion:
Compared to the general population, patients with PsA (followed from the time of diagnosis), and with no prior history of such psychiatric conditions, are at an elevated risk of depression or anxiety, requiring specialised psychiatric care. While an increased vigilance for such comorbidity is thus of importance, the observed risk increase only amounted to around 3 additional cases per 4000 person-years at risk, and there was no elevated risk of suicide.