The Mental Health Act attaches great significance to the “nature or degree” of mental illness. Any psychiatrist who has ever appeared before the First Tier Tribunal will be well aware of the importance of these terms in the Tribunal’s decision making.
In broad terms, ‘nature’ is the course of a disorder and the consequences of it while ‘degree’ is the presentation at that point in time.
The Explanatory Notes for the Mental Health Act 2007 note that “Case law has established that “nature” refers to the particular mental disorder from which the patient is suffering, its chronicity, its prognosis, and the patient’s previous response to receiving treatment for disorder. “Degree” refers to the current manifestation of the patient’s disorder (R v Mental Health Review Tribunal for the South Thames Region ex p. Smith  C.O.D. 148).”
When undertaking assessments under the Mental Health Act in the community, in some cases the patient appears to be symptom free and there is little evidence of ‘degree’. However, in some cases it is necessary to rely on the ‘nature’ of the disorder, particularly where there is an established diagnosis and where there would be risk to the patient or others if they were not treated. Commenting on this very issue, Lady Justice Hale, said, “There are of course mental illnesses which come and go, but where there is a chronic condition, where there is evidence that it will soon deteriorate if medication is not taken, I find it impossible to accept that that is not a mental illness of a nature or degree which makes it appropriate for the patient to be liable to be detained in hospital for medical treatment if the evidence is that, without being detained in hospital, the patient will not take that treatment.”
The issue was also considered in a judicial review of the decision of a Mental Health Review Tribunal for the South Thames Region; at the time of the Tribunal hearing the patient was presenting with neither positive nor negative symptoms of schizophrenia. The patient’s consultant psychiatrist, Dr Eastman, gave evidence that in his opinion the Applicant was suffering from a mental disorder of a nature, but not of a degree, which warrants his detention in hospital. The Tribunal was satisfied on the evidence of “Dr Eastman that the patient is now suffering from mental illness, namely paranoid schizophrenia, the symptoms of which are being well controlled by medication, and that this is now of a nature but not of a degree which makes it appropriate for him to be liable to be detained in hospital for medical treatment, and that such treatment is necessary for his own health and safety and for the protection of other persons”
The judge hearing the judicial review concluded that “It is quite clear that the illness was not of a degree which of itself made it appropriate for him to be liable to be detained. The reason for that was because he has a chronic condition which was static. However, the nature of the condition was that it might cease to be static so that the interpretation that nature is in some way unchanging in one view may be right, but the effect of the condition is that because of its very nature it may not remain static. It seems to me that if the facts upon which the Tribunal rely have shown that it may not be static, that goes to the nature of the condition. The degree in the instant case, in relation to his condition, was not relevant because it was static and stable.”
He went on to state: “If one had simply to look at the degree it would have been right for the discharge to take place, but the nature of the condition was such that it was clear that he should not be discharged.”