What I hate about psychiatric and the mental health field is that you can never truly know when a person is or is not suffering from a "real" mental illness rather than say being over-diagnosed with diagnosis such as "depression" and "anxiety".
There is no doubt that some people really do suffer from serious depression and anxiety, though no-one can definitely tell you what is wrong with these people in any particular case.
There is no test physical test for depression and the symptoms are highly subjective.
A person who wishes for attention or even due to their psychological suggestibility may think or assert that something is wrong with them, such people can easily exaggerate describing the subjective symptoms of depression or other illness in either a conscious or subconscious attempt to obtain diagnosis. There is also the problem of therapists emphasizing and projecting their personal beliefs about mental illness onto certain groups of people. For example why are way more women diagnosed with depression when twice as many men successfully kill themselves? Generally any group with a higher incidence of depression would be expected to have a higher incidence of suicide- except women.
Some people also feel especially sorry for themselves or have poor psychological coping mechanisms or are even suffering moderate grief from losing their pet cat, but they may get diagnosed with depression. I honestly believe some doctors would rather err on the side of caution and diagnose someone with depression that doesn't have it, than risk diagnosing someone who does have it as not having it. I also think some doctors see modern antidepressants as some sort of general preventative or vaccine against suicide and depression "Just in case". "Let's put them on antidepressants just in case their is some chemical imbalance in their brain".
It is for the above reasons I think the incidence of "mainstream" illnesses like depression and anxiety are significantly exaggerated. There is also reasonable evidence that some people are suggestible and that emphasizing they may have "depression" may create the internal perception that they have the disorder, much like giving people a sugar pill is well known to cause many depressed people to respond to treatment because "they believe they need treatment and are receiving it".
No denying depression and anxiety exist- I suffer from both- but there is also no denying that in the average case with non-psychotic features which is not overly severe- you can't be sure with any certainty what may or may not be going on in a persons head in any particular case.
I also feel psychiatric diagnosis can be exploited by people for attention purposes and misguided desires for recognition. I find it particularly suss when people strongly advocate their own mental illness as an excuse for otherwise unacceptable behavior, especially in the case of violent behavior towards others. Everyone is their own advocate.
Also I think psychiatric diagnosis can be abused, especially by teenagers and the gullible.
One of my former best friends when I first met them at 16, seriously told me that they had: Bipolar Disorder, ADHD, Major Depression, OCD, Borderline Personality Disorder and Generalized anxiety disorder. They were tanked up on various meds. I got them to gradually cut them down. Since then they have made massive progress with their problems, and my friend is now perfectly balanced and a good mother to her child, and has no contact with psychiatrists and is not on any medications. As I always said, I didn't really think she had any of that wrong with her in the first place, but she used to thrive on the various diagnosis and almost brag about them.
All of this is just my opinion. You are entitled to yours, none of this is personally directed at any person or group.