Mental illness may not differ from other medical conditions. High blood pressure can occur during numerous illnesses, or even as a normal physiological response to stress. But no one would argue that hypertension isn’t also a “real” medical diagnosis in itself, among individuals meeting certain criteria.
Similarly, painkillers can bring effective relief without correcting whatever biological abnormality necessitates their use. Talk therapies can be very helpful for individuals with psychosis or other disabling symptoms, regardless of whether they target the root biological causes of these syndromes.
Contemporary neurobiological psychiatry, with its heavy reliance on treatment by diagnosis, presumes that each human life with a psychiatric illness is best explained by a disorder of brain biochemistry that needs to be corrected. However, psychiatric conditions and life narratives inform each other.