Hugging, holding hands and caressing give us a psychological boost that is known to be important for emotional well-being and healthy development.

But until now, it has been unclear why we derive pleasure from this kind of touching.

Now researchers at Washington University School of Medicine in St. Louis have identified a neural circuit that transmits the sensation known as 'pleasant touch' from the skin to the brain.

They claim the discovery in mice may help scientists better understand and treat disorders characterised by touch avoidance and impaired social development in humans, including autism spectrum disorder.

'Pleasant touch sensation is very important in all mammals,' said Dr Zhou-Feng Chen, director of the Center for the Study of Itch & Sensory Disorders at Washington University, who led the study. 

'A major way babies are nurtured is through touch. Holding the hand of a dying person is a very powerful, comforting force. Animals groom each other. People hug and shake hands. Massage therapy reduces pain and stress and can provide benefits for patients with psychiatric disorders. 

'In these experiments with mice, we have identified a key neuropeptide and a hard-wired neural pathway dedicated to this sensation.'