Table 1.

Characteristics of the deceased individuals in this study

	Control (N = 39)	Drug usea (N = 14b)	Group comparison P value
Age (year), mean (SD)	54.9 (21.5)	37.5 (12.0)	0.006
Alcohol intake, n (%)	7 (18.0)	2 (14.3)	0.754
Postmortem interval ≤ 6 h, n (%)	32 (82.0)	9 (64.3)	0.173
Cause of death, n (%)			0.015
Accident	17 (43.6)	4 (28.6)
Homicide	3 (7.7)	5 (35.7)
Suicide	2 (5.1)	3 (21.4)
Natural death	15 (38.5)	1 (7.1)
Undetermined	2 (5.1)	1 (7.1)

^aThis group included deceased individuals who had used heroin, amphetamine-type stimulants (ATSs) or ketamine

^bOne of the heroin users without adequate methylation data for the PFC