Three Poisons
In Buddhist psychology, we classify mental maladaptation into the so called three poisons of greed, hate and delusion. This is a rough and ready idea since in most cases there is some mixture and the cut off points are not that clear. Nonetheless, it can be a useful way of thinking.

Basic Life Tendencies
This is because it corresponds to a very basic, primitive level of life. If one thinks of a very simple creature - an amoeba, say - this little blob of life moves along and encounters things which it then has to respond to or not. Some things it envelops and absorbs - food - some things it shrinks from in a reaction of fear and some things it has a confused response to.

So, at the most primitive level, life has these three tendencies. We could say that they are what make life interesting for an amoeba and in so many millions of years we have not progressed very far. We just have a more sophisticated way of being the same.

Theory
Actually, the term delusion can have a broad and a narrow meaning. In a broad sense, all three poisons are forms of delusion, but in the narrow sense of delusion as distinct from greed and hate, mostly has to do with a confused sense of identity. It is more of less synonymous with conceit. Conceit may be agrandising - a deep belief that one is better than anybody else - or denigratory -  that one is worse - or, commonly wild fluctuation between the two. At the core of this is a sense that self-worth matters. From a Buddhist point of view, the healthy position is not one in which a person experiences positive self-worth all the time, but one in which the person stops thinking about self because it does not matter so much.

I think you can see that these two forms - agrandising and denigratory - are themselves forms of greed and hate respectively, so we can say that there are only two poisons - greed and hate, but that delusion in the narrow and usual sense refers when these conditions are directed toward the self rather than toward the external world. Delusion involves more deception and secrecy. Thus, greed and hate are actually less serious conditions than delusion, at least in the sense of being less complicated, closer to the basic life force of amoebic existence, and more on the surface whereas delusion is more deeply hidden.

Eating Disorders
Before we get too lost in theory, let look at an example. Eating disorders clearly fall into this classification. Compulsive eating is a greed condition. Anorexia - self-starvation - is a hate condition and bulimia is a delusion condition. Compulsive eating is based on an overly exaggerated fear that one will not get enough. Anorexia is a longing for the purity of not having to be dependent of anything taken in from outside, seeing it as contamination. Bulimia is a kind of alternating current in which the person iterates a cycle of perfectionism and self-hate, not knowing who or what they are really and copes with the anxiety of life by ritualistically abusing their natural instinctive bodily mechanisms  in relation to food. In all three conditions there is a hidden inner aspect, but in the case of bulimia the whole condition is kept secret and secrecy is part of it. The other two may dissimulate for social reasons, but cannot and do not particularly hide their behaviour so much. We can see that this person is fat and likes cake and that that one is thin and seems to eat nothing, but in the case of the bulimic we might not realise that there is anything of the kind going on at all. However, in this third case, the secret self-confusion dominates everything, creating havoc in relationships and many aspects of daily life even while conventional social forms are superficially maintained. The secret ritual of self-abuse is a substitute for meaning. Instead of engaging with the outside world the person is obsessed by issues of self-evaluation. The cycles becomes ritualistic. In general, ritual can express meaning, but it can also become a substitute for it. The ritual of binge eating and then vomiting to erase the signs of the binging is a kind of expression of futility.

In psychology, everything operates with compensation. There is always a yin-yang effect. Thus, compulsive eating is clearly, in terms of overt behaviour, a greed condition. However, the compensation is that it tends to go with a denigratory self-orientation. The person is fearful. Anorexia is evidently a hate condition. The person rejects the nourishment that comes from the outside world. The compensation is that this tends to go with a secret agrandisement. The person is seeking a purity and superiority - often vis-a-vis their mother - by demonstrating that they can rise above the mere things of this world.

The Example of Shakyamuni
We can see the first two stages of the life of Buddha as being a compulsive phase followed by an anorectic phase. First he had a life of indulgence, then he had a life of ascetic self-punishment. The second was an attempt to over-come the dependency of the first. His compulsivity and anorexia did not just extend to food. They included sex, self-care/mutilation, habitation - in fact, all aspects of physical life. We can thus see that one can be compulsive, anorectic or bulimic in relation to things other than food as well.

Greed conditions tend to be chronic, often low-level and long-lasting whereas hate conditions are more short, sharp and acute. Siddhartha had many years of indulgence then a few years of asceticism. A person may go on being a compulsive eater all their life. If an anorectic person does not actually starve him or herself to death, then they usually come out of the condition after a few years naturally. However, the anorectic condition can often be more severe and life threatening at the time.

Society
Whole societies go through cycles of this kind with lengthy periods of indulgence punctuated by short, destructive periods of warfare. As we reach the stage where military technology is become so hugely destructive that war becomes more and more difficult to contemplate, one could say that society is gradually becoming bulimic, creating a false surface soap opera life behind which all kinds of hidden ritualistic, inhumane practise goes on. Here, for “ritualistic” we could say institutional. The modern, “developed” society projects the idea of the happy family portrayed in so many advertisements, yet is full of rather desperate people whose whole lives seem to be dominated by the stress of playing the institutional game. This institutional game involves massive over-consumption and over-spending - the equivalents of over-eating and vomitting - as people go to work to earn the money to buy the things that are necessary to be the kind of person who can have the kind of job that will pay the money to buy the things that… and so on. While putting on an appearance of normality, people are trapped on a hamster wheel, unable to believe that there is any alternative, yet feeling a gnawing sense of futility.

When people suffer from bulimia or equivalent conditions, it is generally thought that the aim should be to bring them back to normality, but in the modern world, normality is close to being a kind of bulimic condition itself in which much is kept secret and people dare not show themselves just as they are. Surveys that ask people "How many people do you trust and confide in?" have shown a gradually decreasing number. People in general are less trusting. Nobody trusts a handshake contract any more - if it is not on paper it didn't happen. Nbody lets their children walk home from school any more. Although the world is probably no more dangerous than it was, we trust it less. This distrust manifests subjectively as anxiety and stress. We live in a bulimic world.

Liberation
Buddha broke free from this by abruptly re-discovering the sanity of simplicity and ordinary kindness. He suddenly felt love all around him rather than threat and started to share that love with others. Can we?