More stress being single than married?

Are you more vulnerable to life stresses

 if you are single?

A recent study has found that being married or in a committed romantic relationship alters hormones in a way that manages stress and brings a relaxed response to it. 

Is it probably because having a partner produces a sense of support and companionship with which to face life challenges? There is research supporting this point produced by Dario Maestripieri, at the University of Chicago: 

"The results suggest that single and unpaired individuals are more responsive to psychological stress than married individuals, a finding consistent with a growing body of evidence showing that marriage and social support can buffer against stress."

The cortisol levels (stress hormone) of single students were higher than those of their married counterparts...This research doesn't discriminate on the married life quality of non-single students; we know nothing of the variations according to the degree of companionship and support obtained from marriage, only that the fact of being married and not single helps a lot.

 Willing to manage your stress better by making your marriage work?  What about reading more about healthy relationships?