Psychologists and psychiatrists are not epidemiologists; they don't necessarily want to find out causes, even if they should. They want to make the world a better place, which to them usually means progressive , where findings supporting conservative or liberal viewpoints will be judged measureably differently on that basis alone. As Psychology Today notes, in psychology and social work, "there has been a good deal of resistance to evidence-based practice."

For example, when Regnerus authored a study that suggested gay parents had worse outcomes, which led to calls for the journal where he published to be boycotted and the editor to resign, there were no allegations of fraud or the like, to quote the critic's own response to his paper, "Much of the controversy surrounding the Regnerus study involves its political ramifications and questions of the propriety in the review process." and "The acceptance of this article has not only been damaging for same-sex equality, but it also shows the utility of checks and balances in the current peer review system need improving."
His paper could be quite misleading if you didn't look closely, but that is far from unique, check the data on lots of political papers psych papers and they often have far worse mistakes, see how well the conclusions match the results, or the sources actually say what they are supposed to but as long it is favorable to liberal subjects, it gets little notice, whereas Regnerus' underwent an audit and lots of scrutiny for not toeing the progessive line. Even then, they found nothing retration worthy.

These things are further polluted by psychologists, psychiatrist and other academics following in, not wanting to stigmitize certain minority groups, leading to UVA's own Dr. Haidt saying, '"They’ll embrace science whenever it supports their sacred values, but they’ll ditch it or distort it as soon as it threatens a sacred value.”

... But academics can be selective, too, as Daniel Patrick Moynihan found in 1965 when he warned about the rise of unmarried parenthood and welfare dependency among blacks — violating the taboo against criticizing victims of racism."...“Open-minded inquiry into the problems of the black family was shut down for decades, precisely the decades in which it was most urgently needed. Only in the last few years have liberal sociologists begun to acknowledge that Moynihan was right all along.”...Similarly, Larry Summers, then president of Harvard, was ostracized in 2005 for wondering publicly whether the preponderance of male professors in some top math and science departments might be due partly to the larger variance in I.Q. scores among men....“It blamed the victims rather than the powerful. The outrage ultimately led to his resignation." '

Pro-gay groups and anti-fornication conservative groups teamed up to make America think AIDS was a major heterosexual threat in the west and AIDS was not a gay disease, wasting billions on blanket awareness campaigns that could have been spent on AIDS prevention among vulnerable groups. In all these, the science and data wasn't even important enough to verify. The important thing was their ideas wouldn't progress things.

In the end this can lead to a house of cards, as it has before.

To quote the last psychiatrist blog (which goes way more into the depth of the rabbit hole of psychiatry):
"In order for this to be a science, there has to be a testable hypothesis. There isn't any of that in psychiatry. "

Example: antidepressant induced mania is the kind of testable question amenable to scientific investigation. Do they cause it, or not? ... You could do a billion studies on every drug ever made, in every description of "depression" imaginable and that would only allow you to say, "ah, I know the answer in a billion specific situations" but would still have no insights into the nature of the phenomenon.

....

When you give someone Paxil, you are playing the odds: this worked in 25% of the guys we gave it to in 1997. There's nothing wrong with doing this, that's what you're supposed to do; but it does not allow you to speculate on either the nature "antidepressants" or "depression."

...

In physics, such empty theories don't hurt anyone, and there's value in the theory itself. String theory may turn out to be wrong, but you at least are going to be really good at math. Okay.

But in psychiatry these empty questions and empty answers are still applied to social concepts as if they carried the weight of scientific validity. The question of "antidepressant induced mania" may be empty, but that doesn't stop the legal system from using it. You can't imagine the defense proposing that at the precise moment of the murder, the universe split into two equivalent eigenstates and the defendant, in this eigenstate, had been already determined to have had to have been committing the act of murder, which he already had even before he started; but that explanation carries considerably more scientific merit than the psychiatric one, by which I mean both have absolutely none at all.

TLDR:
Psychology is a very soft science, regardless of any access to brain scans or whatever they use to build legitimacy. They are very progressive (in a good and bad way) and are going to say what they think will put them on the right side of history, regardless of costs to scientific understanding.