Table 2. The odds ratios for opiate dependence according to the presence of cavum pellucidum.

	Opiate dependence	Controls	Odds ratio a	95% CI	p value
Categorical measures of CSP	No. (%) of subjects
Presence of CSP	54 (83.1)	43 (64.2)	2.74	1.21 to 6.21	0.016
Presence of large CSP b	12 (18.5)	4 (6.0)	3.64	1.10 to 12.04	0.034
Quantitative measures of CSP	Mean (SD) length of CSP, mm
Length of CSP	4.17 (5.39)	2.27 (2.10)	1.22	1.05 to 1.42	0.011

^aValues were risks for opiate dependence in the presence of the CSP and were calculated by the logistic regression model including age and sex as covariates.

^bA large CSP was defined by the criterion of ≥ 6 mm in CSP length

^cValues were risks for opiate dependence with each 1-mm increase in CSP length and were calculated by the logistic regression model including age and sex as covariates

Abbreviations: CSP, cavum septum pellucidum; No., number; SD, standard deviation; CI, confidence interval