Here’s a hypothesis: there are two broad types of mental disorder, and distinguishing between them might aid in understanding their causes as well as in diagnosis and treatment. The idea springs from my thoughts on the evolutionary forces that have shaped our psychology, particularly in selecting for a diversity of personality types and cognitive styles.
First up, I define mental disorder along pretty broad functional lines as being any lasting psychological condition that hampers an individual’s ability to pursue their interests. I prefer the functional approach (as I do in many cases) rather than trying to dig around to find some essential core or set of features that characterises all mental disorders, but that doesn’t preclude other modes of defining mental disorder.
The benefit of the functional approach is in seeing the mind as an evolved tool, the function of which is to produce behaviours that serve to satisfy our interests (defining what these interests are is another important issue, but I’ll leave that to one side for now).
So, in this light, I propose that there are two broad types of mental disorder:
The first is caused by what might be called a ‘malfunction’ from the normal function of the brain. This might include things like schizophrenia, autism, aphasia, amnesia, Tourette’s and the kinds of things Oliver Sacks writes about.
These can be understood by starting with the normal function of the brain – again defined in functional terms as those functions that enable us to behave in a way that serves our interests – and then looking for specific malfunctions that prevent that from happening.
For example, schizophrenia may be caused in part by a malfunction of the brain structures responsible for the internal monologue, disassociating the inner voice from the sense of self, thus producing a separate voice that can influence behaviour. It might also involve malfunctions of the regions of the brain that process perceptual information before they’re reacted to by higher cognition. Whatever they are, they appear to involve areas of the brain that are not functioning ‘normally’ in the evolutionary functional sense.
Contrasting this could be a second broad type of mental disorder which is simply an extreme version of natural variation in some psychological trait or cognitive style. This might include things like Asperger’s, obsessive compulsive disorder, depression, many affective and mood disorders, phobias, anxiety etc.
Rather than being caused by an outright malfunction, they might be caused by extremes of natural variation. For example, negative emotions serve a functional role of negative reinforcement of the stimuli and demotivating behaviour that might cause those stimuli from reoccurring. There is likely a natural variation in terms of how sensitive we are to negative emotions, how intense we feel them, and in concert with experience, what triggers them and how intensely. Someone who suffers from depression may just be experiencing the normal negative affect, only at a more extreme intensity than is functionally normal, thus impairing behaviour.
Likewise for things like Asperger’s, which may be caused by an extreme of the systematising cognitive style, as defined by Simon Baron-Cohen.
Obsessive-compulsive disorder might be taking our normal concern over order and cleanliness etc and pushing it to an extreme.
In some sense there may be some ‘malfunction’ in these variation-based disorders, but it’s not a fundamental break in the normal function, but instead pushing the normal function to an extreme, thus interfering with normal behaviour.
This is conjectural at this stage. And I profess that psychopathology isn’t my area of expertise. But I am interested in the function of minds, and that raises the prospect of accounting for malfunction. So thought I’d put this out there and see what people think.