Capitalist society promotes a specific kind of thinking for working class people, and for the bourgeoisie, It wouldn't be far fetched to think that psychology could be used as a tool of the capitalist state to influence the superstructure of society.

Treatment for a specific diagnostic is not the same for all groups of people, one known example is that black people in the US are over-diagnosed with schizophrenia while having the same symptoms as white people who were not diagnosed with schizophrenia. This is especially concerning with the use of psych wards as prisons more than places of recovery.

The idea of a chemical imbalance in the brain causing mental disorders is apparently debated between psychologists, which I think makes sense considering that it happens to be a very convenient idea for pharmaceutical companies promoting chemical treatments to disorders. Personally I am not against the use of drugs, but only when the person is completely free to decide their preferred state of their psyche, under capitalism we are not free to choose as we must be as productive as possible to survive.

And besides those things, psychology does have a pretty bad history, like the treatment of women and LGBT+ people, and racism.

However I do think there is a genuine place in society for the study of the mind, and it's unclear to me if the character of psychology is due to science itself having the political character supported by the material base, or if it has always existed as a tool of oppression.