Scientists have long believed that certain types of drug abuse are connected with depression and anxiety at a biochemical level. The evidence to support this theory continues to accumulate at an impressive rate. Research done at the Johns Hopkins Bloomberg School of Public Health indicated that individuals with depression and anxiety were more likely to take prescription narcotics for non-medical reasons (in other words, to abuse them). Read more of this research summary at Medical News Today.
Link Between Opioid Abuse And Mood And Anxiety Disorders