3.1. Sample characteristics
A total of 222 people with psychosis and 215 controls provided information on exposure to bullying. There were no significant differences between psychosis cases and controls with versus without bullying data in terms of demographic characteristics (results, not shown, are available from the authors). The psychosis cases comprised 129 (58.11%) diagnosed with schizophrenia-spectrum disorders and 45 (20.27%) with affective psychosis.
Sociodemographic data by case and control status is presented in . There was no significant difference between psychosis cases and unaffected controls in terms of age and gender, but controls were more likely to have at least GCSE-level qualifications than cases and be from a White British or White Other ethnic background. Sociodemographic characteristics were therefore controlled for in the subsequent analysis.
Sociodemographic characteristics of first-episode psychosis patients and unaffected controls
In terms of lifetime and frequency of cannabis use, controls were more likely to have never smoked cannabis or to have smoked cannabis infrequently while psychosis cases were more likely to have used cannabis every day. Additionally, around a quarter of psychosis cases had a history of conduct problems.
3.2. Prevalence of bullying victimisation by demographic characteristics
Prevalence of bullying victimisation amongst first-episode psychosis cases and healthy controls, stratified also by gender and cannabis use, is provided in . Compared with controls, psychosis cases were approximately twice as likely to report experiences of bullying (p<0.001). This association held when adjustment was made for other life events (Adj. OR 2.28, 95% CI 1.49-3.49, p<0.001). Stratifying by gender, the association between bullying victimisation and being a psychosis case held for both men and women and no statistical interaction by gender was found. Furthermore, significant associations were found between bullying victimisation and having a psychotic disorder regardless of whether individuals had or had not used cannabis in their lifetime (). The numbers of individuals with different frequencies of cannabis use were too small to permit a more fine-grained stratified analysis.
Prevalence of bullying amongst first-episode psychosis cases and unaffected controls as well as by gender and cannabis use
3.3. Bullying victimisation and psychosis-like experiences
presents the prevalence of bullying amongst unaffected controls by presence and absence of PLEs. Previous studies estimated the prevalence of PLEs in the general population within a range from 4% to 28% (Morgan et al., 2009
; van Os et al., 2009
). In our sample the prevalence of PLEs was 15.3%, which falls within the range reported by these previous studies. Amongst controls, those that reported at least one PLE were approximately twice as likely to report exposure to bullying as those without such symptoms, though this association just fell short of statistical significance (p
=0.051). The strength of the association was similar for men and women, when analysed separately, but also failed to reach conventional levels of statistical significance.
Prevalence of bullying amongst unaffected controls by psychosis-like experiences
3.4. Bullying victimisation and psychiatric comorbidity/diagnosis
presents the prevalence of bullying amongst first-episode psychosis cases by psychiatric comorbidity and diagnosis. Amongst the psychosis cases, those presenting with a history of conduct problems were over two times more likely to report experiences of bullying victimisation (p=0.036). In terms of psychosis diagnosis, a higher prevalence of bullying victimisation was found amongst patients with both schizophrenia-spectrum disorders (p<0.001) and those with affective psychosis (p=0.031) when compared to controls. When adjusted for age, gender, ethnicity, level of education and family psychiatric history, the association between being a victim of bullying and history of conduct problems (p=0.020) and diagnosis of schizophrenia-spectrum disorders (p<0.001) held. However, the strength of the association between bullying victimisation and diagnosis of affective psychosis was attenuated (Adj. OR 1.50) and fell short of statistical significance following adjustment for these confounders (p=0.281).
Prevalence of bullying amongst first-episode psychosis cases by psychiatric comorbidity and diagnosis
3.5. Childhood bullying victimisation and psychosis
A total of 133 people were aged 22 or below at the time of interview and thus we can be more certain that their reports of bullying victimisation that occurred 5 or more years previously, were experienced during childhood (prior to 18 years of age). Of these, 64 were cases and 69 were controls. There were significant differences between cases and controls in terms of demographic characteristics (gender, ethnicity and level of education). Controls were more likely to be women (χ2=3.98, p=0.046), to have at least GCSE-level qualifications (χ2=45.84, p<0.001) and be from a White British or White Other ethnic background (χ2 = 14.12 p=0.028) than cases.
We found similar results to those obtained for the overall sample (). Compared with controls, psychosis cases were approximately twice as likely to report experiences of childhood bullying victimisation (p=0.034). This association held when adjustment was made for confounders (p=0.007). Stratifying by gender, a non-significant association between bullying victimisation and being a psychosis case was observed for men (p=0.085) and a significant association for women (p=0.023). Despite a stronger association being evident amongst women, no statistical interaction by gender was found (Likelihood ratio χ2=0.52, p=0.469). Unfortunately, the small size of this subsample did not permit extension of the analysis to testing the potential interaction with cannabis use, comorbidity with conduct disorder or associations for diagnostic subcategories.
Prevalence of childhood bullying amongst first-episode psychosis cases and unaffected controls by gender