If we examine the prayers of the Orthodox Church, we often see that demonic activity is mentioned:
And grant unto us, O Master, when we depart to sleep, repose of body and soul; and protect us from the murky sleep of sin and from all the dark pleasures of the night. Calm the impulses of passions, and quench the fiery darts of evil which are craftily thrown against us; check the turbulence of our flesh, and still all earthly and material thoughts. And grant us, O God, a watchful mind, a prudent reason, a vigilant heart, a tranquil sleep free from all the fantasies of Satan. Raise us up again at the time of prayer strengthened in thy commandments, holding steadfastly within us the remembrance of thy judgments. (from Little Compline)
O holy Angel who accompanieth my wretched soul and lowly life, forsake me not, and depart not from me because of my extravagance and wickedness. Give not access to the evil demon to rule with his might this mortal body of mine,... (from Little Compline)
Demonic temptation is a struggle for all Christians, and addicts have their own unique battles with the demonic because of their compromised wills.
A quick review of demonic activity: the word 'demon' comes from δαίμων in Greek, which is essentially a 'messenger' (this is why you may get a 'mailer daemon' (http://en.wikipedia.org/wiki/Mailer_Daemon#Causes_of_a_bounce_message) when an email bounces, since some programmers have actually read Classical Greek!). Demons bear messages. The other form of this concept is ἄγγελος, or 'angel.'
These messenger spirits come delivering messages. In the case of what we most often refer to as 'angels' (as opposed to 'fallen angels'), these messages come from God the Father. Angels will often communicate clearly and announce plainly where they are from and Who the Lord is. Angels usually appear in visions, but God can even make them appear as live human beings. However, there are times when angels may subtly communicate through thought. After all, they are not material beings and so they communicate to the spirit of those with whom they converse.
Demons or fallen angels, on the other hand, do not bear messages from God, but rather the opposite. They seek to bring man down by provoking his temptations. They bear a satanic message, which is centered on the selfish desires of each person they seek to influence. In essence, when you are following satan, you are following yourself.
Demons are no so much interested in gaining worship for themselves, but getting us to stop following God. They envy our unique position as material and spiritual beings. Therefore, they seek for us to abuse these areas so as to drive us away from God.
How do we know we are being demonically influenced? It is very hard to discern one's thoughts when we spend so much time racing from thought to thought, so we often do not know when we are being 'tempted' by our own selves or a demon is placing a thought in our heads, or, rather, communicating with us. While it may feel like a thought is being put in our heads, it is merely our spiritual nature at work: we are meant to hear on more than just a material level.
So, the discernment of thoughts has always been emphasized in Christianity. You must know whether a thought is coming from your own mind or someone else's.
What panics most people is that they think demons can read their minds, and this is not true. Demons cannot read our thoughts, but having been around people for a long time, they are pretty good at guessing. It can seem like they are reading us when they are in fact not able to access our thoughts. They can only 'speak' to us with feelings, images, and concepts.
Part of an addict's work is to discover his own passions that at once reveal the source of his unhealthy thoughts and what he can be tempted by. Once he knows his temptations, then he also knows where he's going to get punched when he enters the ring.
Demons do not want us sober, because sobriety means growing closer to God. They want us to follow after ourselves. So, the more we seek God, the more we will have to contend with demonic opposition.
Monks, due to their choice to engage the struggle face-on, are often the hardest hit by demonic contention. There are many stories from the Desert Fathers about these battles. The rest of us who live in the world, with its hustle and bustle, rarely spend the time to examine our thoughts and where they come from.
For all concerned, it is important for an addict to understand that he is not always responsible for the thoughts that come into his head, but what he should not do is entertain the unhealthy ones. This is why addicts need 'sponsors,' to review thoughts and see which ones are 'light-bearing' and healthy, versus those that are selfish and destructive.
On the one hand, the Church encourages us to confess all thoughts and ask forgiveness for them all, just because it is safer that way and also because even the thoughts that not our own injure us and we need healing from them. Demons can't punch you, but they can bring you to painful sorrows. Confess these and you will experience great healing.
There is a great deal more to be said about this, but this is enough for now.