3.1. Demographic data
The average age of the participants was 37.5 (S.D. = 13.3) (minimum = 18, maximum = 77). The mean IQ score was 104.6 (S.D. = 12.0) (minimum = 69, maximum = 133). Further basic information on the participants is presented in . There is a spread of participants across socio-economic categories, and the proportion in each category is broadly representative of the United Kingdom population.
Demographic data for the sample.
3.2. Occurrence of traumatic events
At least one traumatic event had been experienced by 70% of the sample (n = 140). Childhood physical or sexual abuse had been experienced by 25.5% (n = 51), with 7.5% experiencing severe childhood sexual abuse (n = 15). A traumatic event had been experienced in the last year by 15%. Endorsement rates for individual events are presented in .
Endorsement rates for each traumatic event.
3.3. Occurrence of persecutory ideation and anomalous perceptions
The mean persecutory ideation score was 22.6 (S.D. = 11.6) (range 16–78). Paranoid ideation was not reported by 42.5% of the sample(n
= 85), and the scores showed an exponential distribution similar to other studies (Freeman et al., 2005
). Verbal hallucinations were reported by 15.5% of the sample (n
= 31), and at least one anomalous experience in the clinical psychosis factor was reported by 44.5%r (n
= 89). There were higher rates for endorsement of at least one item for the temporal lobe (75%) and chemosensation factors (72%).
3.4. Associations of traumatic events and psychotic-like experiences
The occurrence of at least one lifetime traumatic event was associated with a 2.5 times greater risk of endorsing a persecutory thought than not reporting any traumatic event (see ). Similarly, the occurrence of at least one lifetime traumatic event was associated with a 4.8 times greater risk of endorsing a verbal hallucinations item. (These associations of lifetime trauma and psychosis-like experiences remained significant in logistic regressions controlling for age, sex, ethnicity, education level, socio-economic status, and intellectual functioning.) It is also of note that a history of lifetime trauma was associated with higher scores on the Cardiff Anomalous Perception Scale factors of temporal lobe experience, chemosensation, and clinical psychosis (all P-values < 0.01).
Cross-tabulation of history of trauma with psychotic-like experiences.
Type of trauma was also examined (). Using the whole sample, it can be seen that non-victimisation events and severe childhood sexual abuse were particularly associated with psychotic-like experiences. Recent adult traumas did not have an impact. When the group with no history of any trauma was used as the comparison (n = 60), all trauma types, except adult history of physical attack, were significantly associated with the presence of paranoid ideation and verbal hallucinations (P < 0.05). The analysis was also repeated removing the individuals without a history of trauma (i.e. looking within the group who had experienced at least one trauma). Experience of non-victimisation events was significantly associated with both paranoid ideation and verbal hallucinations (P < 0.05). Severe childhood abuse was strongly associated with verbal hallucinations (P = 0.001), and almost had a near-significant association with paranoia (P = 0.056). All other comparisons were non-significant (P > 0.05).
3.5. Mediation analyses
The presence of at least one lifetime trauma was significantly associated with higher levels of anxiety, depression and negative ideas about the self (all P-values < 0.05) (see ). Lifetime trauma was also associated with current use of illicit drugs, Chi-square (df = 1) = 4.586, P = 0.032, odds ratio = 2.14, CI = 1.06, 4.32. The presence of paranoid ideation was significantly associated with higher levels of anxiety, depression and negative ideas about the self (all P-values < 0.01). Persecutory ideation was also associated with current use of illicit drugs, Chi-square (df = 1) = 8.640, P = 0.003, odds ratio = 2.57, CI = 1.36, 4.88. The presence of verbal hallucinations was significantly associated with higher levels of anxiety (P < 0.05), had a trend to be associated with higher levels of depression (P = 0.068) but was not associated with negative beliefs about the self (P = 0.122). Verbal hallucinations were not significantly associated with current use of illicit drugs, Chi-square (df = 1) = 0.749, P = 0.387, odds ratio = 0.68, CI = 0.29, 1.62. Illicit drug use was associated with higher levels of anxiety (P = 0.006), but not significantly with levels of depression (P = 0.058) or negative ideas about the self (P = 0.237).
Levels of affect by the presence of paranoia, hallucinations, a history of trauma, and use of illicit drugs.
Only potential mediation variables that had a significant association with trauma and paranoia or hallucinations were entered into the next stage of the analysis. A binary logistic regression was carried out with paranoid ideation as the dependent variable and a history of trauma, anxiety, depression, negative ideas about the self, and illicit drug use entered as independent variables (see ). Only anxiety was a significant predictor in this model. A similar finding was obtained including age, sex, ethnicity, education, intellectual functioning, and socio-economic status as covariates. A further binary logistic regression was carried out with verbal hallucinations as the dependent variable and a history of trauma and anxiety as independent variables. Both lifetime trauma and anxiety were significant predictors (see ). When age, sex, ethnicity, education, intellectual functioning, and socio-economic status were entered as covariates, then lifetime trauma remained significant (P = 0.021), but the association with anxiety became a trend (P = 0.055).
Binary logistic regressions with paranoia and hallucinations as dependent variables.