Perception of intimacy could depend on the activity of serotonin, a brain chemical.
Understanding the powerful influence of such chemicals is important as supportive close relationships are known to protect against the development of mental illnesses and to promote recovery in those affected by psychiatric conditions. The opposite is also true: dysfunctional relationships can be triggers for those at risk of these conditions.
In the Oxford University research, two groups of volunteers were given amino acid drinks in order to manipulate blood concentrations of the amino acid tryptophan, a vital ingredient in the synthesis of serotonin. One group received drinks that contained tryptophan. The other group received drinks that did not contain tryptophan. They were then asked to make judgments about sets of photographs of couples. Differences in the judgments made by the two groups reflected changes in their serotonin activity.
The volunteers who received the drink without tryptophan consistently rated the couples in the photos as being less 'intimate' and 'romantic' than the participants who received the control drink.
It is already known that serotonin function drops in episodes of depression, where the capacity for intimacy is often compromised.
The results raise the possibility that lower serotonin activity in people with depression and other psychiatric conditions could contribute to changes in the way they perceive personal relationships, or even in their ability to maintain positive personal relationships.
"Although this is only a small study, the same patterns may well extend to the way we perceive our own relationships," said Professor Rogers.
"The ability to chemically influence the capacity for intimacy could be very important. Reduced capacity for intimacy can be a vexing symptom of many psychiatric disorders and an important target for treatment," noted Dr. John Krystal, Editor of Biological Psychiatry. "Drugs that ameliorate the impact of serotonin deficits might play a role in the treatment of this symptom."
Although much more research is necessary before a drug might come to market that can help promote intimacy, it is clear for now that our chemistry has an impact on nearly aspect of our lives, from our most public actions to our most private, as we see here with human intimacy and romantic feelings.