Psychotic-like experiences, which refer to mild delusional or hallucinatory thoughts, are relatively prevalent, occurring in between one-in-twenty (5%) to as many as one-quarter (25%) of adults in the general population (van Os et al, 2009).

Despite their seeming banality, prospective cohort studies suggest that people who report having psychotic-like experiences are at increased risk of a number of adverse long-term outcomes, including: being diagnosed with a psychotic disorder (e.g., schizophrenia) (Fisher et al, 2013), other non-psychotic disorders (Werbeloff, 2012), and suicidal behaviours (Saha et al, 2011).

Findings regarding the latter association, however, have been mixed with a recent longitudinal study failing to find a significant association between psychotic-like experiences after controlling for diagnosis of a pre-existing psychiatric disorder (Sharifi, 2015), highlighting the potential bias caused by cross-sectional studies that have attempted to control for confounding variables (e.g., psychiatric diagnoses) that are also strongly associated with the outcome of interest, in this case, suicidal behaviour (Miller et al, 2001).

Additionally, given the link between psychotic-like experiences and greater severity of psychiatric symptoms, even in those diagnosed with non-psychotic disorders, the association between these experiences and suicidal behaviour may simply reflect the underlying risk of suicide as a function of greater illness severity.

For these reasons, a systematic review and meta-analysis of the literature, including both cross-sectional and longitudinal studies, is necessary to characterise the nature of the association between psychotic-like experiences and suicidal behaviour and, furthermore, to investigate the degree to which the association may be confounded by these methodological differences.

Methods

A systematic review and meta-analysis of three electronic databases (PubMed, PsycINFO, and EMBASE) was undertaken to identify cross-sectional and longitudinal studies on the association between psychotic-like experiences and suicidal behaviour, including suicidal thoughts as well as actual self-injury, attempted suicide, and completed suicide. The period covered by this search was unclear,  although studies published between 1996 and 2015 were ultimately included in the review.

Studies were eligible for inclusion in the review if:

• Data on the association between psychotic-like experiences and self-harm were reported;
• Participants included members of the general (i.e., non-clinical) population;
• Published in English, Dutch, or German.

Outcomes assessed by this review included:

1. Suicidal thoughts;
2. Non-suicidal self-injury (i.e., self-injury where there is no apparent intent to die);
3. Self-injurious behaviour (i.e., self-injury irrespective of whether there was any intent to die);
4. Suicidal thoughts and/or self-injurious behaviours.

Results

Following the systematic search, a total of 25 eligible studies (20 cross-sectional and 5 longitudinal) were included in this review reporting on suicidal behaviour outcomes for a total of 101,798 participants.

The authors found that experiencing psychotic-like symptoms was associated with a significantly increased risk of:

• Suicidal thoughts (Odds ratio [OR] 2.47; 95% Confidence interval [CI] 1.71 to 3.59; 14 studies; 76,216 participants);
• Non-suicidal self-injury (OR 2.36; 95% CI 1.13 to 4.95; 3 studies; 23,100 participants);
• Self-injurious behaviour (OR 3.20; 95% CI 2.33 to 4.40; 20 studies; 89,869 participants);
• Suicidal thoughts and/or self-injurious behaviours (OR 3.03; 95% CI 2.08 to 4.41; 10 studies; 52,005 participants).

The authors next undertook meta-analysis including only those studies in which statistical adjustment was made for depression. The association between experiencing psychotic-like symptoms remained significant for:

• Suicidal thoughts (OR 2.00; 95% CI 1.57 to 2.55; number of studies unclear; 56,827 participants);
• Self-injurious behaviour (OR 2.02; 95% CI 2.33 to 4.40; number of studies unclear; 73,987 participants);
• Suicidal thoughts and/or self-injurious behaviours (OR 2.10; 95% CI 1.65 to 2.66; number of studies unclear; 47,217 participants).

However, psychotic-like experiences were no longer significantly associated with non-suicidal self-injury in those studies that made statistical adjustment for depression:

• OR 1.60; 95% CI 0.80 to 3.10; number of studies unclear; 16,131 participants.

Conclusions

The authors found that the experience of psychotic-like symptoms was associated with a significantly elevated risk of suicidal behaviour ranging from an approximate two-and-a-half fold increase in the risk of non-suicidal self-injury (OR 2.36; 95% CI 1.13 to 4.95) to around a three-fold increased risk of suicidal thoughts and/or self-injurious behaviour (OR 3.03; 95% CI 2.08 to 4.41).

Although adjustment for depression reduced these odds ratios, psychotic-like experiences nonetheless remained significantly associated with an increased risk of suicidal thoughts, self-injurious behaviour, and suicidal thoughts and/or self-injurious behaviours. Psychotic-like experiences were no longer significantly associated with non-suicidal self-injury, in contrast, in those studies that reported effect sizes adjusted for depression. The fact that odds ratios were reduced after adjustment for depression may indicate the presence of unaccounted residual confounding. Results from this review should therefore be interpreted cautiously in light of this.

Limitations

In the first analysis, the review authors included studies irrespective of whether unadjusted and adjusted data were reported, for example, where an included study simultaneously adjusted for multiple possible confounders. Although the approach taken by the authors, namely to include those analyses adjusted for the maximum number of covariates, is generally considered to be a valid selection rule (see Higgins et al, 2011, section 13.6.2.2), combining both unadjusted and adjusted effect sizes within a single meta-analysis is more problematic, as results from such an analysis can be difficult to interpret.

Additionally, the included studies were not independently appraised for study quality by the review authors; a critical step in any meta-analysis (Greco et al, 2013). Given that information gained from assessing the quality of included studies is central to determining the confidence readers can have in the conclusions generated by the review (Greco et al, 2013), failure to appraise study quality considerably limits the research, policy, and clinical practice inferences that can be drawn.

Summary

The authors found that the experience of psychotic-like symptoms is significantly associated with a two-and-a-half to three-fold increased risk of suicidal behaviour and, arguably, should be considered a risk marker indicative of vulnerability to both self-harming behaviour and to suicide.

Further work on this association is necessary, however, given the methodological weaknesses apparent in both the included studies and this review.

If you need help

If you need help and support now and you live in the UK or the Republic of Ireland, please call the Samaritans on 116 123.

If you live elsewhere, we recommend finding a local Crisis Centre on the IASP website.

We also highly recommend that you visit the Connecting with People: Staying Safe resource.

Links

Primary paper

Honingsa S, Drukkera M, Groena R, van Os J. (2015) Psychotic experiences and risk of self-injurious behaviour in the general population: a systematic review and meta-analysis Psychological Medicine 46 (2) pp 237-251. http://dx.doi.org/10.1017/S0033291715001841 Published online: 30 September 2015

Other references

Fisher HL, Caspi A, Poulton R, et al (2013) Specificity of childhood psychotic symptoms for predicting schizophrenia by 38 years of age: a birth cohort study. Psychol Med 2013 43: 2077-2086.

Greco T, Zangrillo A, Biondi-Zoccai G, et al (2013) Meta-analysis: pitfalls and hints. Heart Lung Vessel 2013 5: 219-225 [PMC3868184]

Higgins JPT, Green S (editors) (2011). Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1.0. The Cochrane Collaboration 2011. Available from www.cochrane-handbook.org.

Miller GA, Chapman, JP (2001) Misunderstanding analysis of covariance. J Abnormal Psychol 110: 40-48.

Saha S, Scott JG, Johnson AK, et al (2011) The association between delusional-like experiences and suicidal thoughts and behaviour. Schizophr Res 132: 197-202.

Sharifi V, Eaton WW, Tzy L, et al (2015) Psychotic experiences and risk of death in the general population: 24-27 year follow-up of the Epidemiologic Catchment Area study. Br J Psychiatry 2015 207: 30-36.

van Os J, Linscott RJ, Myin-Germeys I, et al (2009) A systematic review and meta-analysis of the psychosis continuum: evidence for a psychosis proneness-persistence-impairment model of psychotic disorder. Psychol Med 2009 39: 179-195.

Werbeloff N, Drukker M, Dohrenwend BP, et al (2012) Self-reported attenuated psychotic symptoms as forerunners of severe mental disorders later in life. Arch Gen Psychiatry 2012 69: 467-475.

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