"A decision made at the age of 25 might be crystal clear for the individual at that time but might take on other dimensions 20 years later," she wrote in an email to Reuters Health.
"We have, in this study, shown that the men who are accepted for the program were all in the normal range of character and also demonstrated a mature personality and a stable character."
The study, published in the British obstetrics and gynecology journal BJOG, looked at 115 men who donated sperm at clinics in Sweden between 2005 and 2008, comparing them with men of similar age who did not attempt to donate sperm.
Donors in Sweden go through a screening process that weeds out men with psychological or health problems. The study questionnaire asked about behaviors, emotions and social skills.
On two measures, self-directedness and cooperativeness, the donors scored higher than the comparison group, showing that they pursue goals, stick to their values and take responsibility, researchers said.
The donors scored lower on one measure, called harm avoidance.
"This indicates that the sperm donors described themselves as being less worried, uncertain, shy and less subject to fatigue," the researchers wrote.
All other personality traits, including persistence and novelty seeking behaviors, were similar between the two groups.
The results suggested that the donors would not be thrown if a child decided to contact them, said Robert Oates, president of the Society for Male Reproduction and Urology, who was not involved in the study.
"They will be able to handle it if in the future somebody comes to them and says, 'I am your donor child'," he added.
"I think the majority are just nice people who want to help people out. That may be a different personality from the 21-year-old college student who wants to make a lot of money."
Two recent studies have shown that uniting children with donor fathers is usually a positive experience, but the researchers wrote that they were not aware of any children in Sweden taking advantage of the transparency law to contact their biological fathers.
(Reporting from New York by Kerry Grens at Reuters Health; Editing by Elaine Lies)