It is a guessing game because of the nature of the complaints. When your back hurts it is not normal, that is easy to decide. But you have no motivation towards life? This complicates things by orders of magnitude. Maybe you are naturally born that way, maybe you had certain traumas, maybe you had no particular trauma but your upbringing lead you that way slowly, maybe you had shitty friends or family... List goes on. It is even harder for deciding what is normal and what is not. How much sadness or joy should counted as pathological and under what conditions?

Psychiatry has the most subjective organ of interest of all fields in medicine.