This is how the study in question announces the context of the research:
Speculation in public discourse suggests that sexual encounters outside a committed romantic relationship may be emotionally damaging for young people, and federal abstinence education policy has required teaching that sexual activity outside of a marital relationship is likely to have harmful psychological consequences.So the researches set out to prove that casual sex does not damage the participants psychologically (even though it obviously does a lot of damage to the sex-deprived journalists and members of the public, who cannot get over the idea that somebody somewhere is actually having sex and maybe even - the horror! the horror! - enjoting it.)
The results of this study were not surprising: casual sex or "sexual activity outside of a marital relationship" does not cause psychological damage. Why it is necessary to waste resources and time on proving something that is so obvious is beyond my comprehension. Every sane individual must surely know that it's the absence of sex that causes grave psychological harm. It is sad that scientists are forced to dedicate themselves to proving self-evident things simply because a large group of sexually repressed maniacs has colonized public discourse.