Background/Purpose: Psoriasis (PsC) and psoriatic arthritis (PsA) represent common, lifelong inflammatory diseases of the skin and joints (respectively) that are associated with substantial cardiovascular and psychiatric morbidity.  Considering that depression is associated with deleterious cardiovascular outcomes, we investigated the potential long-term impact of depression on myocardial infarction (MI) risk in this patient population. 

Methods: Our analysis employed linked administrative health data, including physician visits, hospital admissions, and death records from Apr 1991 to Mar 2006, and all dispensed medications from Apr 1996 to Mar 2006, for the entire adult (≥18 years) population of British Columbia, Canada (4.1 million individuals).  Inclusion in our incident PsC/PsA exposure cohort required one of the following: 1) ≥2 ICD-9 physician diagnostic codes specific for PsC/PsA within a 2 year period between Apr 1996 and Mar 2006; 2) ≥1 specific ICD-9 diagnostic code from a dermatologist (for PsC), a rheumatologist (for PsA), or from hospital.  Five unexposed, general population controls were matched to each PsC/PsA case by age, sex, and follow-up time (index date).  Individuals with diagnoses of PsC, PsA, or MI prior to the baseline were excluded.  Depression was defined by physician or hospital diagnosis, and MI was defined by hospitalization or death certificate.  We used Cox proportional hazards models to estimate the independent impact and potential effect modification of depression in psoriatic disease compared to matched controls, adjusting for age, sex, comorbidities, health resource utilization, and socioeconomic status. 

Results: Among 10,041 cases of incident PsC/PsA (51% male, mean age of 49 years), 268 incident MI events occurred (incidence = 5.8 per 1,000 person-years [PY]).  The incidence of depression in PsC/PsA was 3.4 per 1,000 PY and the corresponding 10-year prevalence estimate was 21.6%.  Individuals with PsC/PsA were more likely to be depressed (adjusted OR, 1.26) than controls.  Incident depression increased the risk of incident MI by 80% in PsC and PsA (adjusted RR, 1.8; 95% CI, 1.3-2.5).  Further, depression was found to modify the risk of MI in psoriatic conditions such that an increased risk was only observed among psoriatic individuals with depression (RRs = 1.6, P<0.01 vs. 1.1, ns). 

Conclusion: These population-based data suggest that depression is a prevalent and independent risk factor for MI among patients with PsC and PsA.  Moreover, our findings suggest that depression acted as a major effect modifier in the context of PsC and PsA, such that PsC and PsA only led to an increased risk of MI among individuals with depression.  These data underscore the need to actively screen for depression among PsC and PsA patients and closely monitor cardiovascular health in this high-risk group to improve long-term survival.