Objectives Recent studies have found an increased risk of suicide in people on sickness absence, but less is known about to what extent diagnosis-specific sickness absence is a risk indicator for suicidal behaviour. This study aimed to examine all-cause and diagnosis-specific sickness absence and sick-leave duration as risk indicators for suicide attempt and suicide.

Methods This is a population-based prospective cohort study. All non-retired adults (n=4 923 404) who lived in Sweden as on 31 December 2004 were followed-up for 6 years regarding suicide attempt and suicide (2005–2010). HRs and 95% CIs for suicidal behaviour were calculated, using people with no sick-leave spells in 2005 as reference.

Results In analyses adjusted for sociodemographic factors and previous mental healthcare, suicide attempt and current antidepressants prescription, sickness absence predicted suicide attempt (HR 2.37; 95% CI 2.25 to 2.50 for women; HR 2.69; 95% CI 2.53 to 2.86 for men) and suicide (HR 1.91; 95% CI 1.60 to 2.29 for women; HR 1.92; 95% CI 1.71 to 2.14 for men), particularly mental sickness absence (range of HR: 2.74–3.64). The risks were also increased for somatic sickness absence, for example, musculoskeletal and digestive diseases and injury/poisoning (range of HR: 1.57–3.77). Moreover, the risks increased with sick-leave duration.

Conclusions Sickness absence was a clear risk indicator for suicidal behaviour, irrespective of sick-leave diagnoses, among women and men. Awareness of such risks is recommended when monitoring sickness certification. Further studies are warranted in order to gain more detailed knowledge on these associations.