According to the Buddha the ten unwholesome actions are the cause of being reborn as a hungry ghost or "shade".
http://www.accesstoinsight.org:80/tipit ... howto-peta
"Then there is the case where a certain person takes life, takes what is not given, engages in sensual misconduct, engages in false speech, engages in divisive speech, engages in abusive speech, engages in idle chatter, is covetous, bears ill will, and has wrong views. With the break-up of the body, after death, he reappears in the realms of the hungry shades. He lives there, he remains there, by means of whatever is the food of hungry shades. He lives there, he remains that, by means of whatever his friends or relatives give in dedication to him. This is the possible place for that gift to accrue to one staying there."