Table 2.

Levels of sub-threshold psychotic symptoms, as measured using the Comprehensive Assessment of At-Risk Mental State (CAARMS), and schizotypal features, as measured using the Schizotypal Personality Questionnaire (SPQ), in ketamine users and poly-drug using controls

	Poly-drug controls (n = 19)	Ketamine users (n = 17)	Test statistic	p-value
CAARMS severity
Abnormalities of thought content (mean ± SD)	0.4 ± 19	2.5 ± 2	t = 4.2	< 0.001
Abnormal perceptions (mean ± SD)	1.6 ± 1.8	3.0 ± 1.8	t = 2.4	0.02
Abnormalities of speech production (mean ± SD)	1.1 ± 1.5	2.2 ± 1.8	t = 1.9	0.06
CAARMS frequency
Abnormalities of thought content (mean ± SD)	0.2 ± 0.5	2.6 ± 2.2	t = 4.5	< 0.001
Abnormal perceptions (mean ± SD)	0.7 ± 1.4	2.6 ± 1.8	t = 3.5	0.001
Abnormalities of speech production (mean ± SD)	0.6 ± 1.5	2.8 ± 2.0	t = 3.4	0.002
SPQ
Total score (mean ± SD)	11.0 ± 7.3	27.6 ± 20.6	t = 3.2	0.003
Cognitive and perceptual (mean ± SD)	2.6 ± 2.8	9.1 ± 8.4	t = 3.1	0.004
Interpersonal (mean ± SD)	4.2 ± 3.2	9.7 ± 9.0	t = 2.5	0.018
Disorganisation (mean ± SD)	3.8 ± 4.8	8.7 ± 5.2	t = 2.8	0.008