We assessed DIF for three key demographic characteristics (sex, age and race/ethnicity) and three co-morbid disorders (anxiety, mood and personality) across four substances. We did not find consistent evidence for DIF across all these substances and characteristics. The AUD criteria showed no DIF in the six covariates examined. The cannabis criteria showed significant DIF only by age (χ2 = 29.9, p = 0.0009). All cannabis criteria except larger/longer and quit/control contributed to measurement non-invariance by age. The cocaine criteria also showed significant DIF by one characteristic: race/ethnicity (χ2 = 31.6, p = 0.0001). All cocaine criteria contributed to measurement non-invariance except craving. The heroin criteria showed significant DIF by one characteristic: having a mood disorder (χ2 = 44.4, p < 0.0001). All heroin criteria contributed to measurement non-invariance by whether patients had a mood disorder or not.
