A new genetic theory of mental disorders

Yesterday’s New York Times outlines a striking new theory of mental disorders. Put forward by Bernard Crespi and Christopher Badcock — neither of whom works in mental health — the theory goes roughly like this: Genes from the mother’s egg and father’s sperm compete for dominance in the offspring, in what the Times called an evolutionary tug-of-war.

A strong bias toward the father pushes a developing brain along the autistic spectrum, toward a fascination with objects, patterns, mechanical systems, at the expense of social development. A bias toward the mother moves the growing brain along what the researchers call the psychotic spectrum, toward hypersensitivity to mood, their own and others’. This, according to the theory, increases a child’s risk of developing schizophrenia later on, as well as mood problems like bipolar disorder and depression.

This is no less than a unifying theory of mental illness — a theory that puts all mental disorders onto the same spectrum. It naturally has its skeptics.

It does not account for various quirks of autism or schizophrenia, particularly the coexistence of both positive and negative symptoms found in both. Even critics, though, praise the theory for its creativity and plausability. And, though it is limited, there is some biological evidence to lend support to the theory.

Crespi’s name may sound familiar. A biologist by training, he has frequently waded into the murkier waters of sociology, focusing specifically on evolutionary influences in human behavior. In putting forward this theory of mental disorders, he teamed with Badcock, a sociologist. Family therapy has, throughout its existence as a profession, benefited from the contributions of outsiders. Psychology may now be getting a similar shot in the arm.