Can mental disease be diagnosed directly by medical devices?

[kenny1999]

In other words, is there any objective test to find out the problem or differencce of a patient from blood test, CT scan etc rather than assessment by a list of questions or symptoms that we cannot objectively measure or see e.g. feel nervous, feel sad, feel bad

[PurplePuppy]

You can find your answer to your question at this site right below the heading "Getting A Diagnosis":

https://www.nami.org/Your-Journey/Individuals-with-Mental-Illness/Understanding-Your-Diagnosis