I dare you to go over to the research department and tell those “biologists” that they are not scientists because what they are working on does not apply a scientific solution to a problem.
It if weren't for psychology, those scientists wouldn't know what they were trying to scientifically “fix.”
All that said, as an engineer, I understand the position of the snobby scientists. Much the way there are no absolute baselines in “climatology,” much of what is studied as normal and abnormal is in varying degrees subjective.
Deciding who is and who is not “depressed” enough to need such is subjective and (so far) not scientifically determined.
As one in four women in America are currently on mental health drugs - either throughout history 25% of women were CRAZY - or the diagnosis is a bit fast and loose - and self serving.
A monthly counseling session serves the psychologist who diagnoses the depression, and depression has gone from a normal thing that should be temporary to a lifelong condition seems to necessitate life long medical intervention.
I work for a pharma company also.
The Behaviorist school at least tries to quantify behavior in statistical terms, thereby rendering "normal" as an objective value. The danger there is that in doing so, they reduce their patients to little more than statistical abstractions -- dehumanized standard deviations or analyses of variance.
So while psychology isn't the "hard" science that math is, it can be described scientifically, if that evolves to the patient's benefit. However, I doubt that it does.
It if weren’t for psychology, those scientists wouldn’t know what they were trying to scientifically “fix.”
You are describing biochemistry which can have a psychologically measurable result. Even so, most of the drugs perform little better than placebos in the scientific studies.