I think it is fair to say that if you have something influencing your thought processes in a way that bothers you, then you can say that is a mental illness. It might be the common cold, or it might be pneumonia.
It might be of a week's duration, or it might be chronic. It might be self resolving, or it might be fatal. Illness has a lot of variety. If suspected I was mentally ill, I would not seek a psychiatrist's opinion for a
diagnosis. Illness of the brain and its treatment is assigned to one of two branches of medicine. Neurology, and psychiatry. I like to think of psychiatry as the triage ward of neurology. Psychiatry is where you
go when there are no answers and your treatment consists of.....try this medication and see if it makes you feel better. If it does, and that medication is approved for schizophrenia, they might even give you
the diagnosis! Or, if you respond to an anti depressive medication, they might give you the diagnosis of depression. More than likely, they will give you no diagnosis at all, because it doesn't really matter
except for insurance billing purposes. From my personal experience with 5 psychiatrists, I conclude they don't care. It makes no difference to them. Psychiatry is the junk yard of medicine.
What I would do is start in neurology. If I thought my symptoms were significant enough to "bother" me, I would have an Electroencephalogram performed. That could tell me if I have any number of
neurological illnesses that could be responsible for my symptoms. If necessary, I would have an MRI also. Only then would I allow myself to be triaged to psychiatry. If you go to psychiatry first,
they may never find out that you do have a diagnose-able neurological illness. How many psychiatrists would refer you back to neurology for the EEG you never had? Not one of the 5 psychiarists
that treated me for over 25 years ever did so, and it fell to me to discover I was epileptic and an EEG could easily explain many of my symptoms that psychiatry was not adequately addressing.
And when I got the appropriate treatment that was right for me, the majority of symptoms I had experienced for 40 years disappeared. All those symptoms which made no sense, for which I could not make a
connection all went away together, which was surprising because I couldn't see the relationship between some of my symptoms. Physical and mental.