Psychology is a rather young field. It most certainly is not a medical science. Indeed, up until around the beginning of the 20th century, it was nothing more than vague notions and questionable philosophical biases. It is questionable as to wether or not psychology is still more or less the same today. Afterall, it has not been much more than one single century that it has been seriously persued as a science (which is nothing compared to fields such as physics and math, which go back multiple centuries and even millenia) and many of these persuits in themselves are most definitely blunders. The actual medical study of the brain is an entirely separate field from psychology. Psychology is the study of the mind, which is an intangible thing. Psychology is, at best, a highly underdeveloped social science. At worst, it is simply the personal delusions and means of empowerment for men in ivory towers.
It must be pointed out that psychology as a field has an inherent paradox, weakness or loophole within it. Essentially, "the mind" is no less of a philosophical thing to be studying then "the soul" or "the will". If another man tells you that he knows why you acted in a certain way better than you yourself did (I.E. that he knows your will better than you do), there is a 99.99% chance that the man is completely full of it. The mind is not something that was can realistically penetrate with 100% accuracy. We cannot completely deterministically predict the nature and behavior of people's minds with mathematical formulas or testing. Humans are not telepaths, capable of reading eachother's minds, and as such, neither are psychologists. The idea that we can reduce the mind to statistics and actually learn something meaningful from this is nonsense.
The mind is incapable of being measured. Even in seemingly non-tangible or "invisible" areas of science, things can be measured and scientifically observed. Gravity can be measured. Inertia can be measured. Speed can be measured. Time can be measured. Yet the mind cannot be measured. This is what gives psychology such a flimsy basis to begin with. The mind is completely immeasurable by the methods of the natural sciences. As such, the claim that a bunch of men can measure the mind is questionable at best. It is simply impossible to truly "study" the mind in any real scientific sense. It is practically immune to observation. In short, psychology is trapped from the start in that it is impossible to apply any pre-existing scientific methodology to the mind. The mind is intangible to the point where you cannot apply direct observation and traditional scientific methodology to it.
Psychology faces the problem that the psychologists themselves have minds, and are therefore subject to the same fallability as the minds of others that they study and deal with. In short, there will be an inevitable tendency for the "study" to be tainted by the fallable perceptions and/or personal biases of the observer. Further, this tendency will be strongest in the social sciences, where human behavior is what is being observed. If the methodologies of modern psychology were consistantly applied to everyone in the world, the results would show that everyone is insane. Of course, everyone is not insane; this merely demonstrates the inaccuracy of modern psychology.
The minds of human beings may have different reactions to the exact same stimuli. The minds of human beings also have different desires and preferances, and they consist of different ideas. This fact in itself makes the developement of psychological standards practically impossible. There is no objective way for a psychologist to determine and tell you that your thoughts are "wrong". If a girl draws a picture of a pony, and another girl draws a picture of a soldier with a rifle, there is no objective way of determining that one is "right" and the other is "wrong". If a boy draws a picture of a train, and another boy draws a bunch of big blotches of color and "imperfect" geometric shapes, there is no objective way of determing that one is "right" and the other is "wrong".
If John sees a butterfly in the rorsatch image, while Jack sees a demon with horns, there is no objective way of determing that one is "right" and the other is "wrong". If one person believes that UFO's are populated by aliens, while another person believes that humans are the only living creatures in their entire universe, there is no way of determining the sanity of the people on this criteria. If person X thinks that the government should do whatever it wants under any circumstances, while person Y thinks that the government should be abolished, there is no objective way of considering either person "sane" or "insane" on such criteria. Yet modern psychology consists almost entirely of judgements with regaurd to such subjective things.
How does a psychologist determine what behavior is correct and incorrect behavior? There are a number of common methodologies that most psychologists use. One methodology is to use the status quo or majority numbers to determine what "sane" and "proper" behavior is. Another is to outright use personal preferances (wether they be political, cultural, religious or economic) to determine what "sane" and "proper" behavior is. Another is to use a criterion that reflects the personal preferances of people who are higher in authority then the psychologist (such as any higher-up in the buisiness, various government officials and heads of local public school systems).
In either case, no matter which of those methodologies are used, all of them make apriori determinations and generalizations; that is, they assume ahead of time that behavior X will always equal Y and that the appearance of X will always equal behavior Y. This inevitably is going to clash with individualistic variance in humans. You cannot paint droves of people with the same brush in this way. "One Size Fits All" simply doesn't work. Behavior X will not necessarily always have the same motive and purpose for different people. Psychology has of yet to provide any objective criterion by which thought and behavior can be considered "proper" and "improper".
Of course, there are even deeper problems in the three (or four) mentioned methodologies. The method of using the majority to determine correctness is obviously flawed because (1) the amount of people engaging in an activity does not determine its morality or sanity (2) the majority may very well do immoral and insane things sometimes and (3) this method mistakenly paints all individuals and minorities that vary from the "norm" as being mentally disturbed.
The method of using the status quo is flawed because it is inherently "centric". That is, it is biased towards whatever political, racial, religious, social and economic norms exist at the time. Its results may differ from the majoritarian method because the status quo is not always determined by majorities (in some cases it is almost wholly determined by powerful minorities or aristocracies). It nonetheless is inevitably tainted with some degree of political-centric, national-centric, cultural-centric and/or ethno-centric bias.
The method of personal preferances is, to some extent, unavoidable. If the psychologist strongly holds a personal preferance with respect to a particular behavior, it is a possibility that they will consider them to be "proper" and "sane" in their criteria, and therefore deviations are considered to be insane behavior. But this starts to get really interesting when the psychologist is merely functioning as an underling for a set of higher-ups who are determing the criteria. In such a situation, the Psychologist is a tool for powerful people to use in order to mold society into their pre-concieved notions of good people or ideal citezens.
Most frequently, one finds that these higher-ups are governmental officials and those who are well-connected with them. This is apparent both for the public school system and the "private" officies of various shrinks. It is also quite obvious that most psychologists are wedded at the hip to the pharmacudical industry, and therefore the criterion of psychologists may be considerably prone to make a diagnosis as to get people on a particular pharmacudical drug. In this sense, psychologists and the pharmacudical industry are our "legal drug dealers".
One common facade used by all sorts of "social scientists" is that of utilitarianism or subjectivism. That is, they claim to be value-free observers, not inserting anyone's biases or pre-determined structures at all. This obviously is impossible. Noone is a value-free observer and no social science is completely immune from bias and fallability, especially psychology. A claim of subjectivism on the part of a psychologist is hypocritical and paradoxical. If everything was truly 100% subjective, then there would be no purpose to study the mind at all.
Certain things can be deduced, but it can never be determined like a mathematical equation or with absolute certainty because of individuality, spontaneousness and a degree of subjectivity. It still is nonetheless true that certain things can be deduced about the mind, but on a considerably limited basis. In either case, the claim of subjectivism is more often than not just a facade to hide whats really going on; wether that be personal bias, the bias of higher-ups, majoritarianism, "conservatism" (I.E. the status quo as "sanity") or any combination of these things.
A look at the works of Sigmund Frued reveals a psychological model riddled with sweeping generalities that make no sense, the personal biases of Frued and a reoccuring use of the status quo of Frued's environment (predominantly Jewish areas of Eastern Europe circa. turn of the century) as "the norm". Frued had a tendency to classify loads of rather harmless and seemingly meaningless human behavior into signs of paternalism, maternalism and fetal-derived memories.
To Frued, just about everything under the sun could be simply explained away as a manifestation of people's emotional attachments to their parents and romanticism for their fetal stage. What Frued presented us with, in the end, was not a solid new science but a rather wild philosophy that deserves much criticism. Close to a century after the time of Frued, Psychology still does not have any real medical evidence or medical contributions.
Psychology is easily used as a tool to enforce conformity. Anyone who deviates from the generalized and one-size-fits-all criteria is considered as an abnormality to be "fixed". Thus leading to the idea that psychologists can "fix" people (most commonly through subscribing them to a bunch of drugs). Individual variance is anathema to most modern psychologists. Anyone who thinks or acts in a way that is considerably different from the majority of their fellow men is automatically branded as mentally handicapped in some way.
Further, there is a function of guilt that goes on here. The point is to convince the person that they are handicapped as such. The purpose is to make them feel guilty as to their individualistic behavior and therefore stamp it out so that the person conforms to the desired collectivistic behavior that is considered "normal, sane and proper" by the psychological criteria. Someone who has been "fixed" in this way is someone who been tricked into conforming to the preferances of others, essentially. Of course, the individualistic differences and "quirks" of people is almost impossible to truly stamp out completely outside of highly abusive physical and mental treatment.
The use of psychology for social control in this way is expressed most heavily in our political system and school system (especially public). Increasingly, the "school nurse" has more or less been replaced by the "school psychologist". Any student who seems to meaningfully vary from the herd is sent to the school psycholigist, often considered a "trouble-child", has the schoolboard meet with or conspire with their parents, diagnosed with some barely-off-the-books disorder and perscribed with medication. Individual students who are simply bored, eccentric or too smart for highschool are made to go through hell.
These people are more often than not more screwed up afterwards then they were before they were "treated" and loaded full of drugs. The purpose of the school psychologist is obvious: to stamp out the individuality of students as to create a collective ideal. The role of the school psychologist may also more or less be as a spy for the school board or parents. It is a means to pry personal information from students for quasi-governmental purposes.
This works much the same way for adults in our political system as well. Despite the disagreements between the parties, all or most political parties are in complete agreement on a certain core of things. There is a status quo center, if you will, that neither most Democrats or Republicans, and even not most of the independant parties, disagree on aside from a few minor points. People who question any of those "core" agreements are considered to be deviations in the same way as students who don't conform to the flock. They are considered "insane" in their positions.
There is a psychological atmosphere in which you have to fit the "core" criteria or be considered "politically insane". This psychological atmosphere, of course, was created, in part, by powerful people through propagandistic methods derived from modern psychological methodology. Governments have created psychological generalities as criterion for "proper" and "improper" political ideas. Those who do not fit into those generalities are considered "subversive" and "on the fringe". The ulterior purpose, once again, is to instill guilt as to make people conform to the "core" criteria.
A psychologist in general weilds a potentially dangerous weapon over their client. They possess a possible means to control the client. The purpose of psycho-analysis is more than for analysizing. It is for influencing the subject of the analysis. They are to be influenced to adopt a particular pattern of behavior. If the person makes it to the point where they have adopted the desired behavior, the psychologist has suceeded in "fixing" the client. If the person does not make it to this point, the psychologist goes through a whole host of specially-designed methods intended to "fix" the client.
After a certain point, they (those who maintain their individuality) become a nuissance to the psychologist. As such, they are "released", so to speak. This realising is usually coupled with a transferance to other authorities or a quick subscription to a pharmacudical drug. Interestingly, in many cases, these pharmacudical drugs introduce new problems to people's lives, which functions as an incentive for people to keep going to psychologists and seek more "treatment".
Government's role in all of this is quite large. Psychologists depend on licensing from the government to practise their field and are subject to a whole host of regulations, which inevitably introduces political influence into "private" psychological establishments. Not surprisingly, many psychologists are also lawyers. We now have, to some extent, psychologists employed by the state. School psychologists, more or less, have their criteria determined by local and state government (if not federal). Their employment, of course, is entirely dependent on the government. Further, government heavily subsidizes the pharamacudical industry that the psychologists rely on for their diagnosises.
Governments themselves, of course, are ever-willing to create a psychological atmosphere in favor of themselves and in conformity to a certain ideal of citezenship. There is no greater tool than court intellectuals (who in modern times spout lots of psychological constructs) by which such a feat can be accomplished. Psychology is the perfect weapon for people of power to enforce society to conform to their wishes. The purpose is to get rid of as much individuality as possible as to create a collective of drugged-up zombies with no clue as to what's really going on in the world.