Table 5.

 Adjusted odds ratios with 95% confidence intervals for developing schizophrenia any time after conscription for subjects taking cannabis only

Drug use	No of subjects	No (%) of subjects developing schizophrenia	Odds ratio (95% CI)
			Crude	Adjusted*
Cannabis ever†	1635	18 (1.1)	1.9 (1.2 to 3.0)	1.9 (1.1 to 3.1)
Frequency of use of cannabis (ever):
None	36 429	215 (0.6)	1.0†	1.0†
Once	245	0	—	—
2-4 times	499	5 (1.0)	1.7 (0.7 to 4.2)	1.9 (0.8 to 4.8)
5-10 times	255	3 (1.2)	2.0 (0.6 to 6.3)	1.7 (0.5 to 5.7)
11-50 times	176	1 (0.6)	1.0 (0.1 to 6.9)	0.8 (0.1 to 6.0)
>50 times	70	4 (5.7)	10.2 (3.7 to 28.3)	6.7 (2.1 to 21.7)
Linear trend for frequency of use	—	—	1.3 (1.1 to 1.6)	1.3 (1.0 to 1.5)

^*Adjusted for diagnosis at conscription, IQ score, poor social integration, disturbed behaviour, cigarette smoking, and place of upbringing. 

^†No drug use as baseline comparison.