The concept of mental illness

I want to follow up my previous post about the nature of mental illness. The article I've always thought that does the best conceptual analysis of 'mental illness’ is by BA Farrell (see article).

Farrell makes clear that ‘mental illness’ is a statement about psychological functioning. It’s not primarily a statement about statistical abnormality. It standardly implies social maladjustment, but social misfitting is not just due to mental illness. Nor does mental illness necessarily imply bodily dysfunction. As Farrell says, the regulative principles of physical medicine are extended in the concept of mental illness to the psychological reactivity of human organisms. In other words, the psychological functions of the person do not operate within their standard limits when someone is diagnosed as mentally ill. This concept of mental illness fits more clearly with psychotic than neurotic conditions in general, and may well be problematic for personality disorders. What counts as a psychologically morbid process can be open to debate. Applying the concept of mental illness is both descriptive and evaluative in the sense of implying an undesirable and unwelcome state. There are real problems with defining mental illness as behavioural disorder. As Farrell says “all concepts have their difficulties”. We need to work through what we mean by the term ‘mental illness’, rather than merely dismissing it as invalid.

This definition of mental illness is reinforced in an article by Aubrey Lewis. The concept of illness can be ambiguous. It designates a change from a pre-morbid state. As Lewis says, maladaptive behaviour is only pathological if it is accompanied by a disturbance of psychological functioning. Social criteria play no part as such in the diagnosis of illness.  To quote from Lewis: “The concept of disease ... has physiological and psychological components, but no essential social ones”. Doctors may well deal with more than illness. And psychoanalysis generally defines mental illness quite loosely. The recognition of illness may well not be very reliable or valid, and this is even more likely to be the case for mental than physical illness. But Lewis is clear that “it is not possible to set up essentially different criteria for physical health and mental health”.

Psychopathology is, therefore, a morbid process like physical illness. To be diagnosed as mentally ill, a person's psychological processes are dysfunctional. A tweet pulled me up for suggesting that psychosis is maladaptive, as using the word ‘adaptation’, perhaps particularly in the evolutionary sense, may actually explain why people do become psychotic. Psychosis may well increase survival eg. by preventing someone dying by suicide (see my twitter response). I agree that whether mental illness is maladaptive is not the essential relevant criterion to consider. From the individual perspective becoming psychotic may be a necessary reaction. However logical the private sense may seem to the person, it is the loss of common sense viewed by most people that is characteristic of madness. The correctness of our judgments and the soundness of our understanding are subjective but our understanding is also restrained by the understanding of others. As Jaspers said, there may be an 'un-understandability' about psychosis. This applies, however, to others' perspective, as from the individual's point of view a psychotic reaction may make sense (at the time at least).

As both Farrell and Lewis emphasise, our modern idea of illness as physical lesion only really starts from the nineteenth century. The concept of ‘illness’ itself is much more long-standing. Modern critics of the concept of mental illness need to have this longer historical perspective rather than juxtaposing it too much with physical illness and thereby invalidating the concept.