If oxytocin is released in times of closeness and trust, hugging has got to be one of the best activities for getting and giving a nice oxytocin boost.
Newspapers articles are always saying that hugging releases oxytocin, and recommending at least 20 seconds. As far as I know, there's only been one study documenting this.
A 2005 study led by Karen Grewen tested women's blood levels for cortisol and oxytocin before and after 10 minutes of "warm contact" between a woman and her spouse or partner. They weren't exactly testing the effects of hugging itself, however. They wanted to see the relationship between the amount of support a woman perceived from her partner and her blood pressure, stress and relaxation hormones.
The women who in general felt more supported also had lower blood pressure and higher baseline levels of oxytocin. They did NOT find oxytocin increases after the hugs.
Nevertheless, some things you don't need a scientist to prove. I believe that other studies have shown hugging lowers blood pressure and improves health in general.
Here's the paper: <>a href="http://www.psychosomaticmedicine.org/cgi/content/abstract/67/4/531">Effects of Partner Support on Resting Oxytocin, Cortisol, Norepinephrine, and Blood Pressure Before and After Warm Partner Contact