Is Low Libido a Brain Disorder?

by Julian Savulescu

Update: The same misunderstandings are still in evidence, 2 years on (May 2012), for example:  ‘Brain circuitry different for women with anorexia, obesity’

Having started to work in the field of neuroethics a couple of years ago, I have become staggered by the misunderstanding of what neuroscience can tell us. The best example is a recent BBC story which goes by the wonderful title “Libido problems: ‘brain not mind‘” .

It starts by point out, [italics are mine]

“In recent years, a diagnosis of “hypoactive sexual desire disorder” (HSDD) in women has become more accepted by science. However, there remains controversy about whether the term can or should be used to describe a lack of sexual desire, which may be caused by a variety of psychological, emotional and physical factors. The latest study, highlights differences in mental processing in women who have low sex drives.

Its author, Dr Michael Diamond, said it suggested that HSDD was a genuine physical problem… He recruited 19 women who had been diagnosed with the condition, and compared their brain responses with those of seven others using a functional magnetic resonance imaging scanner, which can measure levels of activation in different parts of the brain by detecting increased blood flow. The women were asked to watch a screen for half an hour, with everyday television programmes interspersed with erotic videos. In the seven women who did not have the HSDD diagnosis, increased activity in the insular cortices – parts of the brain believed to be involved in the processing of emotion – could be seen. The same did not happen in the women with HSDD.”

On the basis of this Dr Diamond posits a physical “explanation” for low sex drive in women: “Us being able to identify physiological changes, to me provides significant evidence that it is a true disorder as opposed as opposed to a societal construct.”

There is obviously a physical explanation for sex drive, at one level of explanation. Every mental state has a physical explanation because mental events occur because of activity in the brain. It would be impossible for the brains of two women experiencing different sexual desire (or different thoughts, motivations, sensations or any other mental states) to be exactly alike. There must be differences which explain their different mental states. But these differences in brain activity tell us nothing about what caused the differences in brain activity, which is what Dr Diamond wants to assert.

If I am bored and you are not, our brains will have different activity. If we get a high enough resolution scanner of their activity, we will of course see that the bored brain works differently. But this does not show that boredom is a “true disorder” or “social construct” or anything else.

The brains of women with low sex drive must be different to the brains of women with high sex drive, because they have different drives and mental states! Of course they have different mental processing – they experience different things. The very title of this foray into false explanation illustrates the profound folk confusion between causation and correlation, “Libido problems: brain, not mind”. Our mind is not some spiritual or mysterious thing disconnected from our brain. Our brain activity gives rise to our mind, to our thoughts, feelings and desires.

Dualism is the idea that the brain and mind are separate entities. People like Dr Diamond and the author of the BBC article are folk dualists. Dualism causes us to misunderstand the nature of the relationship between ourselves and our brains.

Even the opponents of this study get it wrong. Sandy Goldbeck-Wood, from the Camden and Islington Mental Health Trust, said that, while interesting, the study could be a “complete red herring”. “She said a bigger study would be needed to make sure that the brain differences identified were truly related to sexual function, as opposed to depression, which could cause sexual problems.”

A bigger study will not solve this issue. And this kind of approach, at least in this simple form, cannot tell us what causes the differences in brain activity.

We can be sure that the brains of women who have low libido are different to brains of women with high libido just as we can be sure that the brains of people who see green are different to the brains of people who see red. What causes those differences could be genetic, environmental or some combination. It is highly likely to be a combination of our inherent biological differences together with key features of our social history.

Looking at a colourful brain scan is amusing, and it makes for an interesting conference presentation, but it can’t tell us that our problems are or are not just “in our minds”, are psychological problems or disorders based on strong intrinsic biological differences. It just tells us which bits of the brain are active when there are differences in emotion.