The word "worshipped" in the Greek means "to prostrate oneself in homage to; do reverence to; adore." The fact that this tormented man in Mark 5:6 ran to Jesus, and not away from Him, indicates that even "demon-possessed" people have a free will and Satan cannot control an individual without his consent.

There have been many battles fought over whether or not a Christian can be demon possessed. The Greek word for "possessed" literally means "to be demonized."  The Bible makes no clear distinction between degrees of demon activity (such as oppressed, depressed, possessed, etc.), but simply refers to people as being "demonized."  All Christians are fighting against spiritual powers.  If we don't put on the whole armor of God, Satan can certainly affect us or even control us.

The best way to administer deliverance is through God's Word.  As a person receives the Word, it will set him free and also help guard against this situation when the demon tries to come back in with seven other spirits. In severe cases of being demonized, the individual clearly needs the help of a believer, and that's the reason why Jesus equipped all believers with authority over evil spirits.

Anointed praise and worship will also drive off evil spirits. One thing reserved for God alone is worship, and the devil has always wanted it. If he can't be the one to receive worship, then he seeks to turn others away from giving true worship to the most High God. 

Praise and worship to the Lord is a powerful tool against Satan. He can't stand to see God worshipped. We worship God in spirit and in truth. The Father seeks those who will worship Him this way.