Oxytocin, a hormone, is primarily known for increasing bonding, social behaviour and closeness between parents, children and couples. Increased oxytocin levels have been found, for example, in partners in functional relationships. In women, it is also produced during the childbirth process and during breastfeeding in order to increase the mother's bond with the baby.
Hugging can also soften your personality. The researchers said someone who hugs loved ones often become more empathetic over time. Neurophysiologist Jrgen Sandkhler, said: ''The positive effect only occurs, however, if the people trust each other, if the associated feelings are present mutually and if the corresponding signals are sent out.
''If people do not know each other, or if the hug is not desired by both parties, its effects are lost.''When we receive unwanted hugs from strangers or even people we know, the hormone is not released and anxiety levels rise.
''This can lead to pure stress because our normal distance-keeping behavior is disregarded. In these situations, we secrete the stress hormone cortisol,'' Sandkhler said. He added that: ''Hugging is good, but no matter how long or how often someone hugs, it is trust that's more important.''
Sandkhler therefore cautioned against the worldwide ''free hugs'' campaign - a social movement involving individuals who offer hugs to strangers in public places.
He said people would only have a beneficial effect ''if everyone involved is clear that it is just a harmless bit of fun.''
Otherwise, it could be perceived as an emotional burden and stress. ''Everyone is familiar with such feelings from our everyday lives, for example, if someone we don't know comes too close to us for no apparent reason.
''This violation of our normal distance-keeping behavior is then generally perceived as disconcerting or even as threatening,'' he said.