Suicide Attempt and Future Risk of Cancer - A Nationwide Cohort Study in Sweden
A self-destructive behaviour is associated with a low level of the hormone oxytocin, which in turn might be associated with an increased risk of cancer development. There are, however, no previous epidemiological studies addressing oxytocin in relation to cancer risk. We hypothesise that a self-destructive behaviour is related to an increased risk of cancer in general, and that the risk is particularly increased in organs where oxytocin receptors are prevalent.
METHODS:
A nationwide cohort study of patients aged 15 years or older with hospitalization for self-inflicted injury or attempted suicide was identified from the Swedish Patient Register in 1968-2011. The outcomes, all different cancer types, were identified from the Swedish Cancer Register. The risk of all cancer and specific cancers or cancer in organs with oxytocin receptors: uterus, breast and brain, in the exposed cohort was compared with the risk in the background population of the corresponding age, sex, and calendar period by standardized incidence ratios (SIR) with 95% confidence intervals (95%CI).
RESULTS:
In total 186,627 patients were hospitalized during the study period, 83,637 men and 102,990 women, generating more than 2.6 million person years of follow-up. Around 30% were younger than 25 years, and 14% were 60 years and older. The SIR for all cancer was 1.3 (95%CI: 1.27-1.33) in men, and 1.25 (1.22-1.28) in women. For oxytocin related cancers the corresponding SIRs were, 1.02 (0.87-1.19) and 1.13 (1.09-1.17) respectively. In those with a clear suicide intent and violent mode the SIR for oxytocin related cancers was 1.04 (0.55-1.78) in men, and 1.16 (0.96-1.39) in women. There was an increased risk for alcohol and smoking tobacco related cancers in both sexes.
CONCLUSIONS:
Patients attempting suicide have an increased risk of cancer, though there seems to be no extra increased risk for cancer in organs with oxytocin receptors.