Background
Delusional-like experiences (DLEs) are common in the general population. Whilst it is well known that psychotic disorders increase the risk of suicide, it is unclear if DLEs are also associated with suicidal thoughts and behaviour. This study aims to explore these variables in a large population-based sample.
Method
Participants were drawn from a national survey of mental health (n = 8841) in Australia. The Composite International Diagnostic Interview was used to identify DLEs, psychiatric disorders, and information related to suicidal ideation, suicide plan and suicide attempts. We examined the relationship between DLEs and suicidal ideation, plans and attempts using logistic regression, adjusted for a range of potentially confounding variables.
Results
8.4% of subjects endorsed one or more DLEs. 12.9% subjects reported suicidal ideation, 3.8% suicidal plans, and 3.0% a suicide attempt at some point in their lives. Those with any DLE were about two to four times as likely to report suicidal ideation, plans or attempts. There was a dose response relationship between DLEs and endorsement of suicide-related items.
Conclusions
DLEs are common in the general population and appear to be independently associated with suicidal thoughts and behaviour. DLE may provide a marker of vulnerability to suicide, and thus could be of value in future suicide prevention research.
Suicide is the end result of complex interactions between biological, psychological, social and environmental factors (Qin et al., 2003). A great deal of research has focused on identifying risk factors and clinical syndromes that are associated with suicidal thoughts and behaviour, with the intention of improving early intervention and prevention services (Bertolote et al., 2005, Mann et al., 2005 and Nock et al., 2010). With respect to serious mental illness, it has long been appreciated that individuals with psychotic disorders such as schizophrenia are at increased risk of suicide compared to the general population (Saha et al., 2007). For example, a systematic review and meta-analysis (Li et al., 2011) that ranked the effect sizes between various mental disorders versus risk of suicide, reported that schizophrenia was associated with highest risk of suicide in males (Relative Risk = 11.8) and was the third highest risk factor for suicide in females (Relative Risk = 12.6).
With respect to the links between schizophrenia and suicide, because schizophrenia is a low prevalence disorder, it has been estimated that this disorder accounts for only about 6.6 to 8.3% of all suicides (Li et al., 2011). Clearly, resources related to the prevention of suicide in those with schizophrenia should be allocated to clinical settings that provide care for serious mental illness. However, whilst psychotic disorders are relatively infrequent, isolated hallucinations and delusional-like experiences (DLEs) are common in the general community. A systematic review (based on 47 publications) reported that the median prevalence of hallucinations and DLEs was 5.3%, but over a quarter of the studies reported prevalence estimates of 14.4% or more (van Os et al., 2009). From a public health perspective, the allocation of resources needs to consider not only the size of the relative risk (i.e. weak versus potent risk factors), but also the prevalence of those exposures (i.e. rare versus common risk factors). Averting common but weak risk factors may prevent more adverse health outcomes compared to averting rare but potent risk factors (Rose, 1992). In light of the prevalence of DLEs in the community, if these experiences are associated with even a small increased risk of suicide, then DLEs would warrant closer inspection from a public health perspective. To date, we are aware of only one study that has directly examined the association between DLE and suicidal thoughts and behaviour. A Japanese study of adolescents aged between 12 and 15 years found an association between psychotic-like experiences and suicidal ideation (Nishida et al., 2010).
The aim of the current study was to examine the association between DLEs and suicidal thoughts and behaviours based on a large population-based study of adults. We hypothesised that individuals who reported DLEs would be more likely to experience suicidal ideation, plans or suicide attempts, and that this relationship would persist after controlling for the presence of common psychiatric disorders (e.g. any depression, anxiety) or other known factors associated with both suicide and DLEs (e.g. drug or alcohol abuse/dependence, trauma or physical disorders).
