A mental health professional will give his or her opinion based on what a person says. The chance of getting more useful insight is likely higher because of the education of the person than a person who barely has any knowlegde about it. I'd say usually it's the person with the problems who knows best what kind of problems they have. A person with 4-6 years of education in a certain area simply has knowlegde about the things this person learned and can easily be wrong, their knowlegde is limited to what they learned in their life.

I've studied things regarding behavior for years, and even though there were so many things I learned, there are also so many things I don't know. I think even if anyone will studie things for 50 years, there will still be a lot of things a person doesn't know. There will always be things that person doesn't know, but an other person, regardless of education, may know something about. Meaning there might be something I don't know, some mental health professional doesn't know, but maybe some other person does know something about because that person might learned something in their life some time that can contribute to useful insight about something.