Psychiatrist and addiction expert Peter DeMaria of Temple's School of Medicine joined "Radio Times" to discuss the science and psychology of addiction. Why do people abuse drugs? "There are two big reasons people use drugs," explained DeMaria . "One is to get high, and the other is to remove this disphoric effect….One of my supervisors once told me about a patient that told him that shooting heroin was like 'instant mommy' — it's that idea of that total warm feeling."