BACKGROUND: Psoriasis is a common inflammatory skin disease, and inflammation may affect suicidal behaviour. Current data on the incidence and risk of suicidal behaviour in patients with psoriasis are scarce.

OBJECTIVES: We investigated the association between psoriasis and the risk of self-harm and suicide attempts and suicides.

METHODS: All Danish patients aged ≥ 18 years with mild or severe psoriasis (cases) from 1 January 1997 to 31 December 2011 were matched on age, sex and calendar time 1 : 5 with healthy controls. The outcome was a diagnosis of self-harm or a nonfatal suicide attempt, or completed suicide. Incidence rates per 10 000 person-years were calculated, and incidence rate ratios (IRRs) and confidence intervals (CIs) were estimated by Poisson regression models.

RESULTS: The study cohort comprised 408 663 individuals, including 57 502 and 11 009 patients with mild and severe psoriasis, respectively. In total 280 cases of self-harm or suicide attempts, and 574 suicides occurred during follow-up. There was no increased risk of self-harm or suicide attempts in patients with mild psoriasis (IRR 1·01, 95% CI 0·17-2·01), but this risk was significantly increased in severe psoriasis (IRR 1·69, 95% CI 1·00-2·84). There was no increased risk of suicides in mild (IRR 1·05, 95% CI 0·84-1·32) or severe psoriasis (IRR 0·78, 95% CI 0·45-1·36). Similar results were found when suicides were confirmed by official forensic investigations, and when psoriasis was compared with atopic dermatitis.

CONCLUSIONS: We found limited evidence to suggest an increased risk of self-harm and nonfatal suicide attempts in patients with psoriasis. Importantly, after adjustment for psoriatic arthritis this risk was no longer significantly increased. The risk of completed suicide was also not increased, regardless of psoriasis severity.