In an initial study they found that violent incidents rose when the home team, Wales, won, rather than lost, regardless of the sport being played. A subsequent study evaluated fans on measures of aggressiveness, happiness and intention to drink alcohol before and after the match.
It turned out that aggressiveness was increased in winning fans but not losing fans. A win did not increase happiness but losing or drawing decreased it and intention to drink was not affected by the match result.
This concurs with the results of a somewhat disturbing study on domestic violence that found that assaults against women in the Washington area specifically increased when the Washington Redskins American football team won.