How can i get my brother off of weed, skunk n maybe others who knows?

i really love my brother n im scared somthing might happen to him hes always smoking weed n skunk, i no this cuz i can smell it n i really want him to stop but if i even try n speak to him then he just tells me to shut up n i think he might be doin it because hes depressed im not sure because start of last year he had a really bad bike accident n he lost his leg n i dnt think hes ever got over it n somtimes hes really nasty n other days he just ignors me n ive left leaflets on his bed before but he just throws them bk in my face so i just wonderd if there was evey a chance of him stoppin. hes 18 n im 14 if dis helps in some way.