Cocaine and heroin abuse
 Patients who abuse heroin get started on opiate pain killers.
(ROOT (NP (NP (NN Cocaine)) (CC and) (NP (NN heroin) (NN abuse))))
(ROOT (NP (NP (NP (NNS Patients)) (SBAR (WHNP (WP who)) (S (VP (VBP abuse) (S (NP (NN heroin)) (VP (VB get) (VP (VBN started) (PP (IN on) (NP (JJ opiate) (NN pain) (NNS killers)))))))))) (. .)))
( ( Cocaine and ) ( heroin abuse ) )
( ( Patients ( who ( abuse ( heroin ( get ( started ( on ( opiate ( pain killers ) ) ) ) ) ) ) ) ) . )